When Facility Executives Need HVAC Upgrades

You want to include a major HVAC renovation in the plan for this year. How do you convince an owner to complete a retrofit that the building needs? You need to demonstrate, first, how the upgrade will improve the building and, second, how this increases the value of the building for the owner.

Some managers may think it is simple to convince an owner to spend thousands of dollars on an upgrade. They assume that an owner will want to complete a project so the building remains state-of-the-art. However, most owners — institutions, for example — view the building as an asset similar to stocks or bonds. They need to see the value of the property increase as a result of their cash outlay.

A second reason commonly given by managers to owners is that the office building will operate more efficiently after the retrofit, thus reducing utility costs. However, tenants usually pay their share of the building’s operating costs based on the amount of space they occupy.

Therefore, the tenants, not the owner, will benefit from the reduced utility costs. The owner pays for the renovation at the time the work is done. The cost of the work is then amortized and passed through to the tenants over the lifetime or payback of the project. The owner will spend the money today and only recoup it over time while the tenants will experience the immediate benefit.

This is the challenge faced by a fictional facility manager we’ll call John Philips, who is responsible for the hypothetical Spencer Building. Built 10 years ago, The Spencer Building is a class A office building in a downtown market. Like many buildings in the marketplace, the 240,000 rentable square foot building is 100 percent occupied with no major leases rolling over for seven to 10 years. Philips is aware that the owner’s objective is to hold this building for at least two to five more years. Although only 10 years old, the building’s HVAC system has two problems. First, the energy management system is not state-of-the-art and does not provide the building with efficient operation and sufficient control. Second, the parts of the mechanical equipment are expensive to maintain.

Philips has recommended upgrading the EMS system and installing variable frequency drives (VFV) on major equipment motors. The upgrade of the EMS system will include new power supplies, bases, transducers, wiring and associated relays. The existing temperature sensors will be replaced and new direct digital controllers will be installed for the interior and exterior air handling units, 24 in all. Static pressure controllers, solar load sensors and control relays will also be added to the EMS, giving the operating engineers more control points to ensure tenant comfort levels and increased monitoring capability. All of the new sensors and relays will be linked by a networking cable in a user-friendly package to a desktop computer with a Pentium microprocessor, graphics card, high-speed modem, color monitor and color printer.

VFDs will be installed on all motors and pumps. VFDs provide a staged start-up of equipment, preventing “spikes,” or sharp increases in electric demand. Motor speed can also be controlled by a VFD to operate more efficiently when equipment is at part load. Other advantages to VFDs are increased equipment life, decreased maintenance costs and automatic restart of equipment after power failures.

The system upgrade was bid to five companies with the recommended vendor bidding on this work for $326,978. The vendor has also given the option of a lease of this system at $422,100 at 11 percent for 60 months. This cost includes energy accounting, bill auditing and benchmarking reports for the first year.

The economic analysis that follows is based on the upgrade package just described; however, a similar approach can be taken with any HVAC system upgrade.

Owner’s Plans

Because the building may be for sale in the next two to five years, Philips knows the owners will want an increase in value at time of sale and a quick return on investment. To prove the increase in value, Philips will rely on the income-capitalization method of appraisal. The income-capitalization method is based on the net operating income (NOI) — the result of subtracting the operating expenses from rents received. If rents go up or expenses go down, NOI increases; higher NOI means higher value.

What’s more, an HVAC retrofit may make a building more appealing to tenants than other buildings in the area, thus increasing rents. Further, a retrofit project usually decreases utility costs.

The income-capitalization method divides the income by a cap rate, defined by market conditions, to find value. Based on the NOI for the building and a cap rate of 9 percent, the current value of The Spencer Building is $50,666,666.

At the Spencer Building, occupancy is already 100 percent with no major leases expiring until the year 2015. Therefore, the upgrade will not attract new tenants so no increases in rent as a result of the project are expected.

However, if the building had vacant space and was located in a competitive market, it might have an edge in leasing over buildings with higher utility costs. A tenant pays operating expenses over a base year. A base year may be set at $10 per square foot. The tenant pays all operating expenses in excess of $10 per square foot; the owner bears the cost up to that amount. If the operating costs are $14 per square foot, the tenant is paying $4 per square foot. If the retrofit reduces costs by $0.50 per square foot, the tenants’ costs fall to $3.50 per square foot. The owner’s costs are not reduced. The benefit to the owner is that the tenant may be happy with the reduced costs and be more inclined to renew the lease.

Cutting Costs

The retrofit at the Spencer Building will reduce costs in several ways. The EMS will improve staging of equipment during start-up and shutdown schedules and increase detail of temperature sensing and automatic adjustment. The VFDs will reduce utility costs by operating at only the speed required to satisfy the comfort load; the current system provides constant volume and constant speed flow. Based on a review of the equipment and historical electrical data, energy savings are estimated at:

• EMS base system utility savings: $96,154


• VFD installation utility savings: $40,872


• Total estimated annual utility savings: $137,026


• Savings per square foot: $2.570

The system costs $326,978. As outlined above, the annual utility savings are $137,026, creating a payback period of 2.39 years. Annual utility savings will increase NOI by $137,026. This, in turn, produces an increase in value based on the income-cap method of $1,522,511. The new value of the building is $52,189,177.

Range of Benefits

Philips can present this project to the owner by citing the benefits of the upgrade. The physical improvements include:

• Improved system control through installation of state-of-the-art equipment


• Cost savings due to VFDs and improved response to temperature


• Ease of operation by use of “point and click” methods


• Reduction of engineering staff time required to program the system and to check concerns through the system rather than a physical site inspection


• Reduced maintenance cost

More important are these financial benefits:

• A payback period of less than 2.5 years


• An increase in value in excess of $1.5 million dollars


• Lower operating expenses for tenants

To win approval for capital projects, a facility manager must have two things: knowledge of the owner’s objectives and the ability to prove the improvements meet those goals. After this upgrade, the Spencer Building will have a state-of-the-art HVAC system and be worth more than before the renovation. This combination will make the building more attractive to potential purchasers. Based on the numerous benefits, the owner would probably approve this upgrade at the Spencer Building.

Geothermal Systems Heating, From the Ground Up

The demand on maintenance and engineering managers to provide comfortable temperatures and good indoor air quality while keeping a tight grip on the budget is among their greatest challenges. On top of the energy costs, there is a maintenance cost for HVAC, boilers, chillers and cooling towers, which can stretch staff skills and time in many directions.

Yet there is a way to provide a high level of comfort without taxing the budget or the staff. The geothermal heat pump systems can cut maintenance and energy costs in half.

How Geothermal Heat Pump Works

Geothermal heat pump systems rely on the temperature of the earth to heat and cool buildings. While there is a variety of designs, the most popular design relies on heat pumps and a closed-loop system of pipes laid under the ground or a body of water.

The efficiency and simplicity of the system is due to the closed-loop system that acts as a large heat exchanger. The loop is filled with a heat-transfer fluid, typically water or a water-antifreeze mix. When a facility requires cooling, heat is transferred from a building to the earth. When heating a facility, heat is absorbed from the earth and transferred to the building.

The system utilizes a heat pump that uses a refrigerant cycle to take low quality heat and concentrate it to high quality heat. Pumps and fans then move the heat.

The system is efficient and simple because it moves heat and does not create heat. In addition, while most mechanical cooling systems work under the same principles, geothermal systems gain efficiency because of the size of their primary heat exchanger — the loop.

At the heart of the process are two thermodynamic principles: Heat always flows from hot to cold, and the greater the difference in temperatures, the higher the rate of heat transfer.

Six to eight feet beneath the surface of the earth, the ground maintains a constant annual temperature from 45 in the north latitudes to 70 degrees in the south. Because the earth’s temperature is stable and the ambient air temperature is not, there is a seasonal differential in most climates that makes the geo-thermal process efficient.

Cost Savings

The relative simplicity of the systems is in part what makes them cost effective. Geothermal heat pump systems do not rely on boilers and cooling towers. Since reversing-cycle technology is deployed at the point of use, there are only two pipes to provide heating and cooling, not four like most conventional systems. And there are no large chillers in the mechanical room or an array of packaged units on the roof exposed to the elements and creating potential problems for the roofing system. All the critical equipment, except the ground loop — pumps, scroll compressors and fans — are inside the building, protected from the elements.

The heat pumps are generally small, which makes them more flexible in terms of design. While some manufacturers will produce 50-ton capacity pumps, most run from 2-10 tons for commercial and institutional markets. To achieve a higher tonnage capacity, multiple heat pumps are linked together. The heat pumps can be fixed in a zone distribution network that allows for point-of-use heating or cooling.

Cost Matters

There are other savings, too. Most of the piping in these systems is polyethylene plastic piping, like gas-line pipe, rather than copper or ferrous-based piping. Ductwork generally is not a part of the installation except for point of use distribution and fresh-air delivery.

There are also maintenance and operational savings. According to the American Society of Heating, Refrigeration and Air-conditioning Engineers (ASHRAE), the annual maintenance cost for a conventional boiler, chiller, cooling tower system is 65 cents per square foot. For a geothermal system that cost is 22-25 cents per square foot. The cost is lower because there is less equipment that needs attention.

Of the maintenance tasks necessary, changing filters was the highest. Less than half as many tasks involved lubrication and checking fan belts, the study notes. There are no water quality problems to worry about. You don’t have to clean or treat a cooling tower. There’s virtually no maintenance to the heat pump. About the only cost is to change filters and maybe check on the circulation pumps’ packings and on the fan belts.

The heat pumps themselves come as self-contained units that are tested at the factory. Even the refrigerant is in a sealed system that requires no checking.

Technology Evolves

Geothermal heat pump technology is energy efficient, offering energy costs about 25-50 percent less than those for a conventional system. Recent changes in the technology have made a significant difference.

The biggest change came when the industry switched from reciprocating compressors to scroll compressors. There was a sizable increase in efficiency there. Manufacturers also started using variable speed fans and compressors. There also have been improvements in reversing and expansion valves in pumps and evaporative coils.

Geothermal heat pump systems have lifespans of 22 years or more and in-ground piping can last 50 years or more. As a result of these and other changes, efficiency has improved. The coefficient of performance for these systems went from 3 to 4.5, and SEER ratings from 13-14 to 17-18. Additional changes in the technology and installation has made these systems better life-cycle investments. For instance, much of the joining of the ground pipe is done in the factory under controlled conditions, rather than in the field. When joints must be made in the field, the tools to do that have been improved. Leaks in the loop are practically unheard of.

Life-Cycle-Cost Advantage

Because a significant portion of the cost of these systems is in the installation of the buried loop, the costs for the whole system begin to decrease as the system gets bigger. Fifty tons is about the breaking point. At that point, the cost of digging more trenches or drilling more wells doesn’t continue to increase at the same rate because the contractor has already brought in his equipment and the work crews are at the site.

The first cost of the system depends on many local variables. Is there competition in the area for geothermal systems? Are well drillers readily available? What is the soil and geology of the area? These systems can more than pay for themselves over the years, avoiding costs on maintenance and roof repairs, and because equipment, principally the loop system, lasts so long, the energy efficiency is really the icing on the cake.

Boilers and HVAC Building Automation Systems

With the newest state-of-the-art sensors, direct digital controls and computer driven expert systems, buildings now can be completely automated and remotely controlled. This article will review what such systems and their operators can and cannot do, what new risks can be created for the boilers in such buildings, and how to reduce and control those risks.

Benefits of automation

Intelligent buildings today use a building automation system (BAS) and other systems to operate HVAC, boilers, chillers, lights, elevators, building access fire protection and other systems to achieve the twin goals of efficiency and comfort.

A BAS is defined here as a system of sensors, pilot devices, logic elements, controllers, peripheral computers, and monitoring equipment providing data to a central computer for energy-efficient control of a building’s internal environment while also providing maximum tenant comfort and equipment reliability.

BAS can deliver energy savings, comfort and maintenance/reliability benefits. These benefits cannot be achieved, however, unless the systems are properly integrated. The system designer must anticipate and overcome the risks outlined below.

Thermal shock

When boiler controls are improperly integrated with the BAS, thermal shock can occur in several ways.

The most common is low return water temperature. In a recent claim, a cast iron hot water boiler suffered a cracked section because of cold water returning from the system. The building was a single-story school, with portions of the building distant from the boiler room.

During the fall, the BAS was programmed to reduce the temperature setpoint on weekends. Water in the zones serving remote areas cooled, and when the BAS attempted to bring the building back to normal occupancy temperatures, a slug of cold water cracked the hot boiler sections.

The problem was solved by putting timers on the zone valves to prevent the simultaneous opening. Controls also were added to maintain a minimum floor through the longest loops during reduced temperature operations to maintain a minimum temperature.

In another case, a store chain reported damage to boilers and air conditioning equipment due to thermal shock when the BAS alternated between heating and cooling. This situation was made worse because all the store locations around the country were connected to a central BAS.

The central BAS computer did not adequately allow for transition from heating to cooling operation and vice versa, resulting in boiler damage and business interruption.

Another form of thermal shock can occur in systems that use a three-way bypass valve. When controlled by outdoor air temperature, these valves allow a high bypass, with reduced flow through the boiler. This reduces the temperature delivered to the loop, thereby saving energy.

The problem occurs when the control is so aggressive that the boiler water stratifies the same way water stratifies in a water heater. In situations where the boiler is called on to deliver only minimum input, the burner will cycle frequently. Since the overall temperature is low, the metal is subjected to much higher stresses than intended or designed for by the supplier.

Thermal shock also has occurred in boiler rooms having outside air inlet louvers controlled by the BAS. Cold outside air entering the boiler or equipment room will chill the boiler. If inadequate precautions are provided, thermal shock, freezing or condensation will occur.

Single-pipe heating and cooling systems area also subject to thermal shock. Single-pipe systems — one piping system for heating and cooling — sometimes are selected for low initial cost. Should both heating and cooling be called for within a short period of time, there is a good chance that chilled water will be admitted into the boiler. Serious thermal shock will result.

Two-pipe systems — using separate piping circuits for heating and cooling — do not completely eliminate this risk. If the BAS incorrectly sequences air handling units and if both heating and cooling coils are in the same unit, air cooled by the refrigeration coils will cool the heating coils. This also will cause cold water to return to the boiler.

Another more common event occurs when the BAS calls for 100 percent outside air to save cooling or heating energy. This usually occurs in shared spaces of buildings that do not require heating or cooling for comfort. Spaces such as foyers, lobbies, hallways or large conference rooms frequently receive 100 percent outside air to address indoor air quality concerns.

The heating coils in the air handling units can be subjected to low temperature. When the boiler starts or the local zone calls for heat, the cold water will shock the boiler.

In spaces requiring very strict temperature and humidity controls, simultaneous operation of the heating — temperature control — and cooling systems — to reduce humidity — is needed. Careful attention to the programming of such heat/cool operation is necessary to avoid the potential for cold water return to a hot boiler.

Condensation

When boilers cool below the dew point temperature of the combustion products, flue gas condensation will occur during the boiler warm-up, causing corrosion on fireside surfaces, breeching and stacks.

Corrosion is another leading cause of boiler accidents. Much of the corrosion can be avoided if the BAS is programmed to maintain boiler temperature at or slightly above the flue gas dew point.

Boiler start-up

When a boiler is first started from a cold condition, both the metal and water are cold. If the boiler is designed to adjust firing rates in response to load changes, it is very important to heat the boiler slowly.

The metal structure must be allowed to gradually absorb the stresses that develop as the metal expands with temperature. Most boiler manufacturers include low fire hold into their boiler controls to provide boiler warm-up. BAS programming must not compromise this protection by premature transfer to high firing.

Multiple boilers (Modular)

For buildings with multiple or modular boilers, the hazards discussed above are more difficult to handle. In such cases, BAS programming must recognize the practical limits of boiler operation for all units.

Other concerns

In addition to the mechanical aspects already discussed, there can be other concerns with control system integrity. A BAS is comprised of sensors, pilot devices, logic elements, controllers, peripheral computers and monitoring equipment. All of these devices are sensitive to some of the following conditions.

Electrical transients

A number of claims have recently been reported involving failure of electrical and electronic devices caused by electrical transients. Common disruptions stem from lighting, internal power fluctuations, harmonics and electric utility problems. Without proper protection, an otherwise harmless power fluctuation can result in damage to the boilers if the BAS fails.

Major utility power problems are infrequent. Lighting arresters, surge protection and current controls have made power in the United States very reliable. One source of localized disturbances is not uncommon, however.

Short duration voltage collapse — a few cycles — can occur when utilities attempt to regulate power factors by compensating for inductive loads with large capacitor banks. When the capacitor bank is engaged, the current inrush causes the voltage to sag, which can cause localized disturbances in the power system.

Boiler/BAS Solutions

CONSIDER THESE RECOMMENDATIONS to address common boiler problems related to BAS:

Thermal shock

• Prevent cold water return by installing three-way mixing valves as a way of limiting the boiler inlet water temperature.


• Consider a small blending pump to prevent temperature stratification in the boiler.


• Control the low fire hold to warm the boiler according to boiler manufacturer guidelines.


• Avoid high fire cut-off when zones are satisfied to avoid rapid temperature change.


• Don’t overlook the air side as a potential source of thermal shock.

Condensation

• Avoid control logic that will increase the frequency of boiler cycling.


• Avoid contact of humid outside air on cool boiler surfaces, or keep the boiler warm.


• Maintain minimum boiler temperature at or above flue gas dew point.

Electrical transients

• Properly ground not only the BAS but also all other equipment. Follow the manufacturer’s instructions.


• Isolate AC power connection to electronics using isolation transformers or equivalent devices.



• Maintain minimum boiler temperature at or above flue gas dew point.

Recommendations

This article has covered areas of concern when integrating heating and cooling equipment with automatic building controls. BAS control programs must recognize the operating limitations of all controlled equipment, as well as the customary energy optimization, HVAC comfort, and building security objectives.

Building designers and owners and maintenance and engineering managers should always follow the recommended practice of the equipment manufacturers. BAS have the ability to control and monitor equipment and alarms from remote locations. Many states have laws requiring boiler operators to be on site in certain situations.

The ability of the BAS to sound alarms based on preset conditions with actions implemented from a remote location should not replace the actions taken by qualified operators on the scene.

Indoor Environmental Quality (IEQ) Problems And Opportunities

In reality, the perfect office doesn't exist today. Evidence that it doesn't, if any is needed, comes from a survey of members of the International Facilities Management Association (IFMA). IFMA asked more than 7,000 facility managers at U.S. corporations to rank the complaints they received most often. At the top of the list, according to the 2,400 respondents, were indoor environmental quality concerns. The biggest complaint was being too hot; number two was being too cold.

Employees responding to another survey reported difficulty doing their work because of poor indoor environmental quality. Those employees specified a number of factors as "stressors." Again, being too hot or too cold were among the top complaints. In fact, all of the top five stressors related to indoor environmental quality (IEQ):

1. Lack of air movement

2. Being too hot in summer

3. Stagnant air

4. Cigarette smoke

5. Being too cold in winter

IEQ is a broader term than IAQ - indoor air quality. IAQ deals specifically with the condition of the air within the building's occupied spaces. IEQ addresses the overall condition of the indoor space. Elements of IEQ include indoor temperature, ergonomics, noise and lighting, as well as the quality of the indoor air.

While there's no distinct line between IAQ and IEQ, what is clear is that the HVAC system has a substantial impact on both areas. What's also clear is that evaluating the HVAC system in light of the broader IEQ concerns can bring important benefits, including improved occupant comfort, reduced complaints and enhanced employee performance.

HVAC and IAQ

IAQ, of course, is a familiar topic for facility executives. It's also an area that's easy to overlook until a problem arises. Often, it is an accumulation of factors that cause the problem. Smoke, odors, dust and high occupancy in an area with too little ventilation all can decrease comfort and affect employee productivity. The U.S. Environmental Protection Agency (EPA) ranks indoor air as one of the top five environmental threats to human health. According to the World Health Organization, 30 percent of commercial buildings show signs of Sick Building Syndrome, including headaches, nausea, irritated nasal passages, itchy eyes and skin irritations.

Most code authorities recognize standards for ventilation air qualities established under ASHRAE Standard, which is based on the maximum possible number of occupants in the building. What complicates the matter is that, in the case of outside air, more is not necessarily better. The problem is how to avoid wasting energy by unnecessarily overventilating a building. Among the solutions are the methods used to control the ventilation, such as time-based ventilation, demand-based ventilation, carbon dioxide sensors and mixed gas sensors.

Controlling humidity

Humidity plays an important role in indoor environmental quality. If it gets too low, it causes respiratory problems, particularly for people with allergies, sinus problems or asthma. If it gets too high, more places become breeding grounds for microbial growth.

ASHRAE standards suggest relative humidity levels should be maintained between 30 percent and 60 percent. That means at times humidity needs to be added to the air and at other times it must be removed.

High relative humidity can have an impact on absenteeism and increases the potential for respiratory illnesses among workers. When relative humidity exceeds recommended levels, humans are adversely affected. Our sinuses are affected when humidity is too low and our skin dries out. Too high humidity causes different bacteria to propagate in mechanical systems.

There's another advantage to controlling humidity directly. The building owner can reduce energy bills in the heating season by reducing the temperature that would otherwise have been maintained and increasing the relative humidity within healthy ranges. The opposite can be done in the summer. Raising the temperature above what would otherwise have been maintained and lowering the humidity allows the body to evaporate moisture off the skin to stay cool.

While humidity and airborne contaminants are traditionally considered in IAQ analyses, other important IEQ factors may not be. Consider air movement. So many people look at IAQ from a system level and they tend to overlook what's happening in the occupied space. ASHRAE spells out rules for selecting a diffuser based on an air diffusion performance index (ADPI). An ADPI of 80 or higher assures adequate air movement.

Temperature is another issue that isn't always included in discussions of IAQ. One rationale for excluding temperature is that IAQ should be limited to health and safety issues.

Unfortunately, that distinction doesn't matter to building occupants who are complaining about their space. Rightly or wrongly, complaints about temperature are often attributed to poor indoor air quality. What's more, it can be difficult to separate health issues from ones tied to comfort.

Equally important is that employees who are uncomfortably hot or cold are likely to be less productive than they would otherwise be. That's one more reason facility executives are better off taking the IEQ approach to analyzing interior space.

Gains from good IEQ

A report for the National Energy Management Institute states that even in healthy buildings, a 1.5 percent productivity gain is possible when IEQ measures are instituted. In fact, the 1.5 percent gain is the conservative estimate; the report says that gains may be as high as 10 percent.

Productivity gains are not the only benefits from improving indoor environmental quality. Good IEQ also is good business.

To the building owner, good IEQ is a very clear plus. When you have good thermal comfort and good acoustic comfort, it differentiates your building from your competition. You can market your building as a clean and comfortable environment in which to work.

Analyzing IEQ

There are four basic steps to take. First, listen to your occupants and understand what they are saying about the building's indoor environmental quality. The second is walk through the building checking for those things and take specific measurements for those problems. The third step is to go back to the source - the HVAC system, for example - and take measurements there, making sure the equipment is doing what it is designed to do. The fourth step is to document any revised design or maintenance procedures that are taken to correct the problem. You also want to incorporate an occupant response mechanism for feedback to make sure you have corrected the problem.

Before making HVAC improvements, facilities executives need to conduct an economic analysis. Often, this analysis is based on utilities costs and savings. But, payback periods for HVAC improvements are much shorter when all major cost elements are added to the analysis. Such factors as building operating costs, salary costs and current productivity losses that could be regained shorten the payback period for proposed improvements.

Indoor environmental quality can be improved in nearly every building. And a number of steps can improve quality without costing much. In fact, many steps are just good facilities management.

You need to do proper maintenance of the building. Set up a checklist on a periodic basis and keep a log of all maintenance of your HVAC system. Do carbon monoxide monitoring for ventilation and make sure all controls are operating properly.

Facility managers and their staff need to fully understand how the HVAC and other systems in their buildings were intended to work and keep them operating in that manner. When major remodeling occurs or changes in space occupancy or usage, the ventilation and thermal requirements of the space need to be reviewed. When replacing equipment, the facility's staff needs to be involved in the selection, location and installation of the new equipment. This can help assure that the equipment will meet their needs and that they understand how it is to be operated and maintained. Building managers should also demand that the systems and equipment selected meet the currently established standards-of-care in that industry.

There are many solutions to indoor environmental quality problems, but it's not wise to wait for the crisis. Facility executives are better off looking now, before they have a problem. Chances are they'll find a number of IEQ issues that need to be addressed that can be handled at next to no cost. Half the issues that arise involve simple things your inhouse staff can do, like changing filters, cleaning drain pans, using high efficiency vacuums in housekeeping and so on. When you wait for the complaints, you are in a reactive mode trying to find a Band-Aid when you could have a more serious situation. If you consider IEQ now, you can take a more holistic approach and prevent your building from experiencing many IEQ problems.

Given all things on the facility agenda, it can be tough to find time to tackle a problem that no one is complaining about. But being proactive can pay off. One direct benefit is that, over the long term, a preventive approach will save time, perhaps a significant amount of time. There's another plus: Facility executives who can show senior managers that their actions have increased employee satisfaction or productivity are positioning themselves as problem-solvers and are demonstrating that the buildings they manage are assets, not costs.

The HVAC Systems - Overlooked Opportunities To Improve IAQ

The new HVAC technologies and approaches promise reductions both in first costs and long-term operating expenses, and herald improvements in indoor air quality.

Low Temperature Air Distribution

A relatively new approach to HVAC system design - one that's being employed increasingly often in new buildings and major renovations - lowers the temperature of the chilled air distributed through the facility. The chief advantages of this approach lie in reduced first costs and in longer-term savings realized through reduced "churn" costs.

When chilled air is distributed in the range of 46-48 F (as opposed to 55 F, the benchmark in conventional systems), less air is needed to cool interior spaces, so ductwork and piping can be significantly smaller than in conventional systems. That downsizing of air and water flow, in turn, means fans and pumps can be smaller. Fans operate continuously when spaces are occupied, but because less air is required to do the same job, energy costs also drop.

Air that arrives at an interior space at such a low temperature, however, cannot be released directly into the room. Dumping 46-48 F air into a room through a ceiling diffuser would likely cause some very real discomfort. But if the cold air is combined with room air before it enters the space, it can be brought to an acceptable temperature - warm enough that the occupants below won't feel cold downdrafts.

This blending of chilled and room air can be accomplished by a fan-powered mixing box, set in the ceiling, that will produce a constant flow rate while varying the proportions of chilled and room air.

Experience shows that if the blended supply air is within the 50-52 F range, it will mix well enough with room air near the ceiling (typically about 75 F) that no discomfort will result.

Demand-controlled Ventilation

Making sure that the air-change rates in interior spaces and the volume of fresh air being brought into a space conform with standards set by the American Society of Heating, Refrigeration and Air-conditioning Engineers (ASHRAE) can be an expensive proposition - especially in the summer, when warm, moist outside air must be cooled and dehumidified before being used for ventilation. One way to cut down on those refrigeration/dehumidification costs is through a demand-controlled ventilation system that modulates the quantity of outside air being brought into the building as occupancy and pollutant levels change.

The ability to know how much outside air should be brought into a space at any given time has been greatly enhanced by the refinement of low-cost electronic monitoring devices that accurately measure carbon dioxide levels. (Sensors that monitor other contaminants, such as volatile organic compounds, are also available, though their relatively high cost has so far limited their use.)

Demand-controlled ventilation can be incorporated into systems that mix fresh air with room air as well as into systems that have separate ducting for fresh air supply. Because installing an independent fresh air delivery system is fairly costly, however, the potential benefits of such a system must be carefully weighed against its substantial first costs.

Filtration Choices

As useful as they are - and as crucial as they've proved to be in improving indoor air quality in facilities - the fresh air standards set by ASHRAE are bedeviled by one basic problem. The standards necessarily assume that the air being brought into a building is clean. In reality, there can be an enormous variation in the quality of outdoor air, depending on factors such as time of day and a facility's location. And it is difficult to predict how the general air quality at a location might change, for better or worse, over time.

Given this unpredictability, owners and developers of new facilities or those undergoing extensive renovations may wish to ask their consulting engineers to specify very high efficiency filters - as high as 85 percent efficiency - especially in some densely populated urban areas.

Owners may also be wise to instruct consultants to build extra space into designs for air-handling units so that additional filters - or higher-efficiency filters - can easily be added later if the quality of outdoor air declines or if, for example, the owner wants to attract tenants with very strict air quality requirements. If that space is not built in, the cost of installing additional filters later may be prohibitive.

The small additional cost of building-in that space at the start may be very easy to justify if the business environment changes in the future. For instance, if a commercial rental market should turn sharply competitive, the ability to ensure high indoor air quality might give an owner a much-needed edge in attracting prospective tenants.

Sizing Systems for Real-World Demand

For generations, good HVAC engineering practice has demanded that systems and components be sized large enough to accommodate peak use. For the most part, however, engineers have sized systems by textbook standards instead of real-world conditions. Because they have had little actual performance data from which to make their calculations, engineers have also tended to increase sizing even beyond what's necessary to accommodate a theoretical peak load in order to to protect against under-capacity.

Sizing in this way creates systems that are far bigger than they need to be. Sizing systems to accommodate conditions that never occur is unnecessarily expensive for two reasons: First, there's the added cost of buying equipment that's bigger than a building is ever going to need; second, the part-load performance of most equipment (e.g., fans and pumps) is generally much less efficient than that equipment's full-load performance.

When energy is cheap, those part-load inefficiencies may not seem to matter so much. But when energy prices go up, such inefficiencies could boost operating costs enormously.

It may be difficult to see the mistake that's being made when an air conditioning system is unnecessarily oversized. If a facility contains a certain amount of heat-generating equipment, shouldn't the cooling system be built big enough to handle the load that would occur if all that equipment were running at once?

The answer is no, for the simple reason that it's extremely improbable that that would ever happen. For example, sizing chillers for a hotel should not be based on the sum of the peaks of all rooms, public spaces, and back-of-the-house areas. Calculations of cooling needs using such a sum might easily exceed 2.0 to 2.5 tons per room, including public areas. But the actual operating experience of hotels shows that total chiller sizing should be based on use in the range of 1.5 tons per room including public and back-of-house areas.

Obviously, each project must be reviewed individually. However, monitoring actual building use provides a sound basis for establishing diversity in lieu of design-day calculations and guesswork on diversity values. Building owners can be of great help to engineers if they keep actual records of equipment use, calculate performance data and make this information available to the design community. In some cases, leaving enough space to accommodate future additions of equipment is a good approach for avoiding initial oversizing.

For typical office buildings, lighting and equipment are the largest components of cooling loads. With advances in lighting design, typical open workspace can be easily reduced to 0.8 to 1.0 watts per square foot. Equipment loads, on the other hand, tend to be more difficult to estimate because of "diversity" - that is, the fact that patterns of actual use are constantly changing and that peak loads do not occur simultaneously throughout a facility.

Despite increases in office equipment use, however, office power on a gross-area basis does not usually exceed 2.0 watts per square foot. Nevertheless, hot and poorly ventilated spaces are common in many older buildings where new "high-tech" tenants are occupants.

Given this experience, convincing design engineers and owners not to oversize air-conditioning systems when designing for new construction is difficult. But systems that take advantage of diversity from space-to-space and floor-to-floor are usually effective at matching active loads without oversizing. Air-based systems that can vary temperature in sequence provide the most flexibility. Fan-powered mixing boxes that vary primary air while keeping ventilation of the space high for good air quality are efficient devices.

Moreover, this kind of system can be combined with low-temperature air to provide additional cooling capacity without a high-premium first cost. Variable air volume systems, which can deliver colder air if required but can be reset at a higher level when average conditions exist, are very efficient and allow for "built-in" capacity without much penalty on first cost.

Chillers that have from 10 to 20 percent additional capacity allow chiller temperatures to be reduced by 1 to 2 F. This is more cost effective for meeting high-load periods than adding a chiller to serve infrequent peaks.

Underfloor Air Distribution

One approach to HVAC system design that emphasizes the "air side" has been receiving a great deal of attention lately: low-pressure underfloor air distribution. In this approach, cool air, which is kept at a slight positive pressure, is distributed through access-floor plenums and delivered to occupied spaces through diffusers set directly in floor tiles, from which it rises toward ceiling return vents through a natural convective process, removing heat and contaminants from the space as it travels upward.

Underfloor air distribution offers multiple advantages over conventional supply-air delivery methods, including greatly enhanced individual control of comfort conditions, long-term reductions in energy consumption and improvements in IAQ. Still, the first costs associated with underfloor air, though falling, remain relatively high as compared with those of conventional systems, and an access floor system probably cannot be financially justified on the basis of air distribution alone. When underfloor air is coupled with access-floor power and voice/ data grids, however, the numbers become a lot easier to live with - especially in offices with high churn rates where the ease of reconfiguration that's possible with plug-and-play systems can lead to mind-boggling reductions in the use of outside contractors.

There's one trend that's sure to make underfloor air distribution a viable alternative for a wider range of buildings in the near future: the progress being made in developing window glass that can regulate solar transmittance and heat rejection.

Today, the implementation of underfloor air systems is mostly limited to building interiors. In heavily glazed buildings, it has been necessary to supplement or replace underfloor air delivery at the perimeter with more conventional systems that are better able to handle the huge swings in temperature that can occur even over the course of a single day.

New glass technologies that immensely improve the efficiency of the building envelope will likely be on the market within the next decade. When that happens - perhaps as soon as five years - it will no longer be necessary to install a separate system to handle the heating/cooling needs of the perimeter, and the overall short- and long-term costs of underfloor air systems will drop precipitously.

Given all the new alternatives, facility executives can't make decisions based on what's been done in the past. Instead, the focus must be placed on applying those technologies that make the most sense in a given situation - and on simplifying and integrating systems. "Rules of thumb" provided a better road map when HVAC system goals and technology options were fewer and less complex than today.

Having a master plan, defining clear long-range goals, and making sure that systems are as simple and integrated as possible is the most sound advice that can be offered as HVAC technologies and approaches to system design continue to change.

State-Of-The-Art Design And Technology Can Meet Both Energy And Comfort Demands

The CFC phaseout has forced facility executives to take a hard look at their HVAC systems. At the same time, current technology offers significant opportunities for energy savings from the heating and cooling system, typically the second-largest energy user in commercial facilities. On top of all that, the definition of comfort has evolved rapidly over the past decade.

At one time, HVAC systems satisfied the comfort issue by simply making sure the work area was warm or cool enough for most occupants. Now, comfort is being refined to include indoor air quality and outside air exchange.

All in all, it's a tall order: The HVAC system is expected to achieve comfortable conditions for the individual and the masses in the office without harming the delicate global atmosphere. A good example is the CFC phaseout.

Facility executives have three choices: contain CFCs in existing chillers, convert existing units to alternative refrigerants or replace existing machines. Installing new high-efficiency equipment can result in significant energy savings.

Modern HVAC equipment offers improved efficiencies, which are being achieved with better motor performance and better temperature splits in the refrigerant tubes. Today's HVAC systems also offer better part-load efficiencies than older models. Multi-stack units and horizontal screws run more efficiently at part-load levels than earlier models. The economizer bundles are better than they used to be, so the systems run more efficiently.

The recent improvements in chiller efficiencies are the result of refinements in many small places. Manufacturers have done it by better designed compressors, by improving heat transfers. Every component has been reengineered.

New materials, notably plastics, offer major potential for increased HVAC advances that end up benefiting building owners and managers. New materials make units more efficient, easier to install and more corrosion resistant. HVAC systems are becoming more component oriented so they can be put in after the building is built.

Resolving IAQ via HVAC

One of the biggest challenges facing facility managers today is how to meet ASHRAE's current standard for outside air exchange. Variable air volume systems and normal applications need to be reexamined to meet ASHRAE fresh air standard.

To maintain energy efficiency and meet the new standard, multi-zone air-handling systems may need some overhauls. The normal unit has two decks -- one for warm air and one for cool. Provided air is mostly being recirculated, the two decks work effectively.

With the larger temperature differences involved with increased outside air, a neutral zone also may be needed. In a triple-deck system, the outside air is brought by the heat exchanger to that neutral point, before entering the air stream. The result is returned efficiency to the HVAC system in its heating and cooling modes.

Another promising solution is the use of dessicants to pre-condition air without mechanical cooling.

For buildings undergoing major retrofits, the building's air should be tested before renovations begin. Establish the levels of existing contaminants, if any, so that you have a point of reference. After renovations, the air quality should be retested. Periodically, additional IAQ tests should be conducted.

What should building owners do when indoor air actually is better than outside air, as often is the case in buildings located adjacent to major airports? Filtration for gaseous contaminants can play a major role in cleaning the building's air. The health care industry already is aware of the importance of air filtration in controlling the spread of airborne pathogens. But other building owners are just beginning to recognize the importance of proper filtration systems.

Custom comfort

Many advances have been made in HVAC control technology during the past decade. One of the most recent is the ability to control air flow, temperature and even air quality at individual workstations. Because of metabolism and dress in the office, women often complain that they are too cold, while men are too hot.

Advances in DDCs and control systems give us tools to get better air as well as energy conservation from HVAC systems. Everything now is automatic. We can set certain parameters for temperature and humidity with the outside air economizer.

And we can do so much more with the system to protect the health of the people inside the building. For example, if there is a fire and the smoke-detection system is activated, the HVAC controls can stop the air-handling system and start exhausting smoke from the space while alerting local fire and alarm departments.

Electronics in HVAC systems are becoming more integrated with each other: The air-handling unit knows how much is needed from it, and the chiller knows what each air handler is doing and can adjust itself accordingly.

Further refinements in HVAC system controls are on the near horizon. For example, comfort control that relies on more than the temperature to measure a space's overall comfort currently is being investigated by researchers, consulting engineers, ASHRAE and building controls manufacturers. Sophisticated comfort control sensors are being developed that will take into account not just the dry-bulb temperature of today's thermostats but also the mean radiant temperature, air velocity and humidity level.

Julian Arhire is a Manager with DtiCorp.com - DtiCorp.com carries more than 35,000 HVAC products, including industrial, commercial and residential parts and equipment from Honeywell, Johnson Contols, Robertshaw, Jandy, Grundfos, Armstrong and more.

Taking Charge of Indoor Air Quality (IAQ)

As sick buildings become more visible, inaction is a liability. This situation begs the question: "Will you be ready when dissatisfied occupants, reporters and lawyers show up at your building?" As part of an overall preventive due diligence program, an IAQ audit can show good faith and quality management.

Making headlines

Most publicized incidents involving IAQ problems have involved moisture and microbial problems. For instance, an employee in a branch of the New York Library complained of respiratory illness. Even though the library had undergone an extensive renovation a few years earlier, basement flooding problems persisted.

A consulting group was brought in to investigate, and found a mold - Stachybotrys atra - that has been implicated in numerous sick buildings. The exact health effects of this mold are not clear, however. The building was closed, and other library branches were investigated. As a result of these additional investigations, two other branches were closed.

IAQ audit

An IAQ audit involves periodic inspection of an IAQ program to ensure practices are carried out and procedures are followed. In its simplest form, it involves a visual inspection of the building and its HVAC system components. A more comprehensive audit includes this inspection, along with a review of a building's:

• design documents


• training program

• written IAQ plan, including policies and procedures

• on-going documentation, such as complaint reports and maintenance records

• any IAQ or medical reports.

Fortunately, many useful resources exist to facilitate the audit process. For commercial buildings, the EPA's Building Air Quality guidance document contains blank forms that can be used to structure and conduct an audit. For educational facilities, EPA's IAQ Tools For Schools guidance kit contains practical checklists that can be used in an audit. An audit template accompanies this article on page 9, but any checklist used should be tailored to a building's specific needs.

Typical legal scenario

No legally established definitions exist as to what constitutes "good" IAQ in terms of design, operation and maintenance of HVAC systems or controlling indoor air contaminants. What should maintenance and engineering managers do to provide a healthful indoor air environment, given the lack of definitive standards?

Managers should base their conduct on industry standards developed by organizations such as the EPA, the Occupational Safety and Health Administration (OSHA), and the American Society of Heating, Refrigeration, and Air-Conditioning Engineers (ASHRAE), since the courts turn to these sources for guidance.

If managers can show that they are making a good-faith attempt to manage their facilities according to prevailing standards, their legal exposure to IAQ litigation will be minimized. How do managers show a judge or occupant they are making such an attempt? Documentation is key.

Building audits are an important process that managers should perform consistently in the course of building management. Aside from ensuring IAQ, audits can create necessary documentation to demonstrate good-faith IAQ efforts. A quality building audit provides a manager with tangible evidence that the building and its components have been assessed for current problems.

Regular building audits, much like regular medical check-ups, are preventive. They indicate a diligent, rather than an indifferent, management style, which can minimize legal exposure.

Air quality improvement

Maintenance and engineering managers need to meet rising occupant expectations each day, and they need to show a concerted effort is under way to maintain acceptable IAQ. Essentially, this is the concept of continuous quality improvement being applied to buildings: the air quality improvement process.

An IAQ audit can be a useful tool for isolating the areas on which management should focus. IAQ audits can pinpoint potential areas of concern, areas where preventive efforts are successful, areas that require the establishment of policies and procedures and areas where staff training is needed.

Implementation tips

The most effective way to start an audit program will depend upon a facility's in-house maintenance and engineering expertise. If a building's staff is well trained in IAQ and experienced with buildings and HVAC systems, managers can customize a checklist for the building, and audits can be performed periodically -at least once a year.

If in-house expertise does not exist, a consultant can be brought in to conduct the audit. During this third-party audit, appropriate personnel should accompany the consultant to learn how to conduct the audit themselves. It may be helpful to use photographs to document observations of the building and HVAC system.

The auditing process and the resulting observations can serve as a valuable training tool for all those charged with IAQ responsibilities.

After any audit, the auditor should brief members of the IAQ team on the resulting observations and suggestions. Managers should retain the completed audit checklist for future reference, and they should address problems in any areas that require corrective action, making sure to document the process.


With the increase in sick building visibility, inaction is a liability. After all, you never know when your IAQ might start making headlines.

The Elements Of An Efficient HVAC System

Today's systems are designed to meet stricter environmental, indoor air quality and user requirements. Many of the gains in HVAC system efficiency have come as the result of improvements in the operating efficiency of key system components. Other gains are the result of the use of technologies that are either new, or new to the HVAC field. Even the use of computer-aided design tools have helped system engineers design HVAC systems that perform more efficiently.

Although there are many individual advances that have helped to improve HVAC system operating efficiency, much of the overall improvement can be attributed to five key factors:

- The development of low kW/ton chillers;

- The use of high-efficiency boiler control systems;

- The application of direct digital control (DDC) systems;

- The use of energy-efficient motors; and,

- The matching of variable frequency drives to pump, fan and chiller motors.

For years, building owners were satisfied with the performance and efficiencies of chillers that operated in the range of 0.8 to 0.9 kW/ton when new. As they age, actual operating efficiencies fall to more than 1.0 kW/ton at full load.

Today, new chillers are being installed with full load-rated efficiencies of 0.50 kW/ton, a near 50 percent increase. Equally impressive are the part-load efficiencies of the new generation of chillers. Although the operating efficiency of nearly all older chillers rapidly falls off with decreased load, the operating efficiency of new chillers does not drop off nearly as quickly.

Chiller design changes

Several design and operation changes have helped improve chiller performance. To improve the heat transfer characteristics of the chillers, manufacturers have increased the size of the units' heat exchangers. Electromechanical control systems have been replaced by microprocessor-based electronic controls that provide greater precision, reliability and flexibility. Variable frequency drives control the speed of the compressor, resulting in an increase in part-load performance.

Increased energy efficiency is not the only benefit of the new generation of building chillers; these chillers offer better refrigerant containment. Although older chillers routinely may have lost 10 percent to 15 percent of the refrigerant charge per year, new chillers can limit losses to less than 0.5 percent. Lower leak rates and better purge systems reduce the quantity of non-condensable gasses found in the refrigerant system -- a key factor in maintaining chiller performance over time.

Another significant development is in boiler operation: the replacement of pneumatic and manual controls with microprocessor-based systems. As a rule of thumb, the systems can be expected to achieve energy savings of 5 percent to 7 percent over conventional pneumatic-based systems.

Microprocessor-based control systems achieve their savings primarily as the result of their ability to modulate the boiler's operation more accurately than pneumatic-based systems. By modulating the boiler's operation accurately, the systems help to maintain the proper fuel-to-air ratio and track the load placed on the boiler by the HVAC system.

Microprocessor-based systems offer several additional advantages, including remote monitoring and operating capabilities, automated control sequences, monitoring of steam flow, and reduced maintenance costs. One way the systems can help reduce maintenance costs is through their ability to maintain proper fuel-to-air ratio. By maintaining the proper ratio, the systems reduce the rate at which soot collects on boiler tubes, thus decreasing the frequency of required tear down and cleaning. Keeping the boiler tubes clean of soot also helps to improve the thermal efficiency of the boiler.

Direct digital controls

A major change in the HVAC field is the widespread implementation of direct digital controls (DDC). Introduced more than 15 years ago, DDC systems have become the industry standard for control systems design today. With the ability to provide accurate and precise control of temperature and air and water flows, the systems have widely replaced pneumatic and electric control systems.

DDC systems help building owners save energy in several ways. Their accuracy and precision nearly eliminate the control problems of offset, overshoot, and hunting commonly found in pneumatic systems, resulting in better regulation of the system. Their ability to respond to a nearly unlimited range of sensors results in better coordinated control activities. This also allows the systems to perform more complex control strategies than could be performed with pneumatic controls. Finally, their simple or automatic calibration ensures that the control systems will perform as designed over time, with little or no loss of accuracy.

DDC systems also offer several other advantages. Because the control strategies are software-based, the systems can be easily modified to match changes in occupant requirements without costly hardware changes. DDC systems also are ideal for applications that benefit from remote monitoring and operation.

Energy-efficient motors

Today's HVAC systems are making use of energy-efficient motors. Energy-efficient motors offer a moderate but significant increase in full-load operating efficiency over standard motor designs. For example, an energy-efficient 10 hp motor operates at about 93 percent efficiency; a standard motor of the same size is typically rated at 88 percent. Similarly, a 50 hp energy-efficient motor is rated at approximately 94 percent efficiency in contrast to the 90 percent efficiency rating of a 50 hp standard motor.

This increase in operating efficiency accompanies a first-cost increase for the motors. How rapidly this additional first cost is recovered depends on two factors: the loading of the motor, and the number of hours the motor is operated per year.

The closer the motor is operated to its full-load rating and the greater the number of hours per year the motor is operated, the quicker the first-cost differential is recovered. For most applications where the motor is run continuously at or near full load, the payback period for the additional first cost is typically between three and six months.

The combination of constant loading and long hours of operation have made HVAC applications well-suited for the use of energy-efficient motors. Energy-efficient motors commonly are found driving centrifugal circulation pumps and system fans. With these loads, the 4 percent or 5 percent increase in the electrical efficiency of the drive motor translates to a significant energy savings, particularly when the systems operate 24 hours per day, year round.

A side benefit of energy-efficient motor design is its higher power factor. Increasing the power factor of a drive motor reduces the current draw on the electrical system, frees additional distribution capacity and reduces distribution losses in the system. Although increasing the power factor isn't enough of a benefit to justify the cost differential of the higher efficiency motor, it's an important consideration, particularly for large users of electricity where system capacity is limited.

Although the motors have demonstrated themselves to be very cost-effective in new applications, their use in existing applications is a little more difficult to justify. In most instances, the cost to replace an existing, operating motor with one of higher efficiency will not be recovered for five to 10 years or longer.

Of the improvements in HVAC systems that have helped to increase operating efficiency, variable frequency drives have had the most dramatic results. Applied to system components ranging from fans to chillers, the drives have demonstrated themselves to be very successful in reducing system energy requirements during part-load operation. And with most systems operating at part-load capacities 90 percent or more of the time, the energy savings produced by variable frequency drives rapidly recover their investment, typically within one to two years.

In general, the larger the motor, the greater the savings. As a rule of thumb, nearly any HVAC system motor 20 hp and larger can benefit from the installation of a variable frequency drive.

Variable frequency drive applications

Variable frequency drives produce their savings by varying the frequency and voltage of the motor's electrical supply. This variation is used to reduce the operating speed of the equipment it controls to match the load requirements. At reduced operating speed, the power draw of the drive motor drops off rapidly.


For example, a centrifugal fan, when operated at 75 percent flow, draws only about 40 percent of full-load power. At 50 percent flow, the power requirement for the fan decreases to less than 15 percent of full-load power. While conventional control systems, such as damper or vane control, also reduce the energy requirements at partial flow, the savings are significantly less.

Another area where variable frequency drives have improved the operating efficiency of an HVAC system is with centrifugal pumps found in hot and chilled water circulation systems. Typically, these pumps supply a constant flow of water to terminal units. As the demand for heating or cooling water decreases, the control valves at the terminal units throttle back. To keep the pressure in the system constant, a bypass valve between the supply and return systems opens. With the flow rate remaining nearly constant, the load on the pump's electric drive also remains nearly constant.

Variable frequency drives regulate the pressure in the system in response to varying demands by slowing the pump. As with centrifugal fans, the power required by the pumps falls off as the load and speed are decreased. Again, because most systems operate well below design capacity 90 percent of the time, the savings produced by reduced speed operation are significant, typically recovering the cost of the unit in one to two years.

Chiller loads

A third application for variable frequency drives is centrifugal chillers. Chillers are sized for peak cooling loads, although these loads occur only a few hours per year.

With conventional control systems that close vanes on the chiller inlet, chiller efficiency falls off significantly during part-load operation. When variable frequency drives are applied to these chillers, they regulate the operation of the chiller by reducing the speed of the compressor. The result is near full-load operating efficiency over a very wide range of cooling loads. This increase in part-load efficiency translates into a 15 percent to 20 percent increase in the chiller's seasonal efficiency.

Energy conservation isn't the only benefit of variable frequency drives. A strain is placed on an electric motor and the mechanical system it drives every time a pump, fan or chiller is started at full-line voltage: Motor winding becomes heated, belts slip, drive chains stretch and high-pressure is developed in circulation systems. Variable frequency drives reduce these stresses by starting systems at reduced voltages and frequencies in a soft start, resulting in increased motor and equipment life.

Finally, the most important element in an energy-efficient HVAC system is how the system is operated. No matter how sophisticated the system, or how extensive its energy-conserving features, the system's performance depends upon the way in which it's operated and maintained. Operating personnel must be properly trained in how best to use the system and its features. Maintenance personnel must be trained and equipped with the proper tools to keep the system operating in the way it was designed. Maintenance cannot be deferred.

Energy-efficient HVAC systems offer the facility manager the ability to improve system performance while reducing energy requirements. But they benefit building owners only as long as they are taken care of. If facility managers choose to ignore maintenance requirements, they may soon find systems malfunctioning to the point where they have actually increased the requirement for energy.

10 Questions To Ask Before You Choose A Roof

Choosing the correct replacement for an aged roof - or identifying the best choice for a new building - is no easy task. The perfect roofing solution for one building may be the worst option for another just down the street. That's because no two buildings are precisely alike, even if they closely resemble each other. So how do you choose a new roof, given all the choices in the marketplace? You can start by asking a series of questions, before you choose the roof, the roofing contractor or the manufacturer.

1. What is this building's mission statement?

Before calls are made to roofing contractors or manufacturers, the first item to address is the company's mission statement as it relates to the building.

Whether you are building new facilities or managing existing properties, you want to be confident that the roofing systems you select deliver the performance you expect. More often than not, the building itself dictates the appropriate roofing system specification.

You need to know as much about the building and its future as possible. Does the company plan to keep this building as part of its real estate assets for the next 10 to 20 years? Are there any plans to expand it in the near future, or to change its use? What are its current and future occupancy, insulation requirements, aesthetic priorities and even the maintenance schedules for rooftop equipment?

These and other mission statement issues will help shape answers to types of roofing to consider and how much of the capital budget is really needed for the job.

Start your questions with what is the building going to be used for. If it's a spec building, maybe you only need a basic roof. But, if the facility has a special use, such as an airline reservation center with computers in it, then your considerations for roofing options are quite different.

For example, as more companies move toward operating 24 hours daily, seven days a week to satisfy global customers, the data center must never spring a rooftop leak. Water on computer systems generally spells disaster.

A special set of concerns arise for cooling-dominated climates. Does the roof contribute to air conditioning savings and address other key issues? Is it part of a total energy program? There is a growing concern about urban heat islands. Reflective, white roofs have become of interest in those areas for a few reasons. They keep the building cooler, reduce air conditioning costs and also minimize the heat-loading of the surrounding environment.

2. What physical and other elements influence the roofing system selection?

After identifying the goals and mission of a facility, it's time to evaluate the building itself. You need to begin by looking at the building's location and the attributes of its surrounding area. You need to examine building codes, weather trends, topography - even the direction the building faces.

The physical characteristics of the building are also crucial: size, shape, design, height and age.


You also need to look at the construction materials used to build the facility and the location of HVAC and fire protection equipment, particularly if either or both of these are partially or totally housed on the rooftop.

When it comes to roof replacement, you need to list the attributes of the roof area itself. It's best to detail the roof's size, shape, slope, deck construction, edge detailing, protrusions, rooftop access and existing roofing system. Along with this basic information, you need to find out why the original roof is no longer adequate.

3. What flexible-membrane roofing options are available?

SPRI, the association that represents sheet membrane and component suppliers to the commercial roofing industry, identifies three major categories of membranes: thermosets, thermoplastics and modified bitumens.

Thermoset membranes are made from rubber polymers. The most common is EPDM, often referred to as "rubber roofing." These membranes are well suited to withstand the potentially damaging effects of sunlight and the common chemicals found on roofs. They are easily identified on the rooftop. Just look at the seams. Thermoset membranes require liquid or tape adhesives to form a watertight seal at the overlaps.

Thermoplastic membranes are based on plastic polymers. The most common is PVC, which is made flexible by adding plasticizers. Thermoplastic membranes have seams that are most commonly formed using heat welding. Most thermoplastic membranes are manufactured with a reinforcement layer, usually polyester or fiberglass to provide increased strength and dimensional stability.

Hypalon thermoplastic begins as a thermoplastic, but cures over time to become a thermoset. Like other thermoplastics, Hypalon materials are heat sealed at the seams.

Another thermoplastic hybrid is thermoplastic polyolefin (TPO), which combines the attributes of EPDM and PVC. TPO membranes do not cure after exposure to the elements and remain hot-air weldable throughout their service life. Most TPO membranes are reinforced with polyester, fiberglass or a combination of the two, but unreinforced TPO membranes are available.

Modified bitumen membranes incorporate the formulation and prefabrication advantages of flexible-membrane roofing with some of the traditional installation techniques used in built-up roofing. Modified bitumen sheets are factory-fabricated, composed of asphalt which is modified with a rubber or plastic polymer for increased flexibility, and combined with a reinforcement for added strength and stability.

4. Which type of membrane and attachment system are best for the building?

Many factors determine the best system for a particular building. For most buildings, there are a number of options and advantages that need to be weighed against the facility's mission statement. The decision should not be made only on the basis of cost. Other important considerations for membranes are building height, wind exposure, anticipated roof traffic and aesthetics.

The attachment system also depends on the specific building's characteristics. If the roof deck is able to withstand the weight, a ballasted roof may be the best option. But, if the slope of the roof is greater than 2 inches every foot, this system may not be appropriate. There are other limitations to ballasted systems, such as roof height, proximity to shorelines and other high wind zones, and the availability of ballast.

A steel or wood deck that easily accepts fasteners makes a good substrate for a mechanically fastened membrane. These systems can be designed to provide the necessary resistance to known wind forces and are not subject to slope limitations.

Another alternative is the fully adhered system, in which the membrane is attached to the prepared substrate using a specified adhesive. Depending on the membrane, the adhesive may be solvent- or water-based or asphalt. The finished surface of an adhered roof is smooth.

For those concerned with building aesthetics, colored membranes can make an attractive contribution to the building's appearance.

5. Does all roofing material delivered to the job site bear the UL label?

If not, specify that it must. This is the only way you can guarantee that the roofing materials installed on your roof are the same materials tested by Underwriter's Laboratories. Additionally, be sure that the roof assembly you buy or specify, which includes the insulation, is UL-classified and -labeled. Using an insulation other than what was tested with the roofing membrane may void the UL classification. If the UL Building Materials Directory does not list the roofing system you are sold, insist on verification of the classification in the form of a photocopy of the UL's letter of approval.

Make sure that the product you are getting is the actual product that was tested. You don't want something that is similar but not equal. Look for the label at the job site and make sure all components of the system were tested together. You want the membrane tested with the insulation that you are using on your building.

6. Does the system require a wind uplift rating?

Wind uplift damage can be extensive and expensive. Accepted as an industry standard, American Society of Civil Engineers Standard 7-95, "Minimum Design Loads for Buildings and Other Structures," can be used to determine the wind zone of the building. Wind uplift testing, such as that performed at Factory Mutual or Underwriters Laboratories, can be used to determine that the selected roof system meets or exceeds the local wind uplift requirements.

7. How much does the completed system add to the dead load weight of the roof structure?

In choosing any reroofing option, the facility executive should be aware of the load-bearing capacity of the roof deck to make sure the right flexible-membrane option is chosen. In new construction, savings in structural steel can often be achieved by installing one of the lighter flexible-membrane systems.

A ballasted thermoplastic or EPDM roof may require in excess of 1,000 pounds per 100 square feet, while a mechanically attached or fully adhered thermoset or thermoplastic membrane weighs 33 pounds per 100 square feet. A lighter system often allows you to reroof directly over your existing roof, while the heavier ones may require you to tear off the old roof and begin anew. But weight is only one consideration in the selection of a roof membrane and attachment system. A ballasted roof may be the best choice for a given facility. Facility executives must assure that all relevant considerations, including weight, are taken into account in the decision-making process.

8. What are the expertise and financial strengths of the roofing contractor you are considering?

Roofing contractors need to be chosen with great care. The introduction of new roofing materials and application techniques within the past 10 years has led to many changes. A professional roofing contractor should be familiar with different types of roofing systems, to help you make the best decision for your facility, based on your budget.

Ask the contractor if his or her company is a member of a local, state, regional or national industry association. Contractors involved in professional associations generally are better informed on the latest developments and issues of their industry.

Insist the contractor supply you with copies of insurance certificates that verify workers' compensation and general liability coverages. Check that those coverages are in effect for the duration of your roofing job. If the contractor is not properly insured, your company, as the property owner, may be liable for accidents occurring on the property. Also check your state's licensing requirements and find out if the contractor is bonded by a surety company.

The installation of different roofing systems varies considerably. Education and training are the most important elements in the installation of roofing systems. Make sure the roofing contractor you choose has had detailed and ongoing training on the system being installed.

One rule of thumb is to find out if the contractor has installed at least 100,000 square feet of the system you want in the past 18 months. Also, make sure the contractor is approved by the manufacturer to install that specific system.

The quality of workmanship is crucial to good roof performance. The National Roofing Contractors Association offers a professional roofing selection guide. In addition, many manufacturers have approved contractor programs with specific qualifications that roofers must complete before approval.

9. What is warranted and by whom?

There are two basic categories of roofing warranties. The contractor's warranty typically covers workmanship. The manufacturer's warranty covers at least the materials, though many cover additional items. Even if the manufacturer's warranty is broad, it will not completely protect you if the roof is improperly installed.

Carefully read and understand any roofing warranty offered and watch for provisions that would void it. For example, it's nearly impossible to avoid all ponded water. Ponded water can be caused by a clogged roof drain or deflection of the roof deck in between the support columns. Proper roof maintenance can help assure that the warranty remains valid. Be aware of warranty language that voids the guarantee.

Most professional roofing contractors will offer periodic maintenance inspections throughout the year. These inspections help ensure your project complies with the standards specified in the warranty. A typical maintenance program consists of a detailed visual examination of the roof system, flashing, insulation and related components to identify any potential trouble areas.

More important than the warranty, however, is getting the right flexible-membrane roof on your building in the first place. If the roof is correctly designed and installed to meet your facility's needs, building codes and geographical considerations, and the warranty covers those needs, you probably will be enjoying the benefits of a flexible-membrane roof many years after the original warranty expires.

10. After the roof is installed, what after service and educational programs are available for the facilities management team?

Seminars offered by roofing industry associations like SPRI and manufacturers can be invaluable ways for the building's roofing team to expand their understanding of commercial roofing system types, installation processes and maintenance considerations. Specific courses are available to help building owners and facilities managers learn more about various roofing systems, materials and components; insulation and accessory products; elements of roof design; contractor selection; warranties and maintenance considerations.

Energy Efficiency And HVAC Technology

The following overview offers a quick reference to key considerations with some of the most effective technologies. As with lighting, trial installations are a good idea; so is working with manufacturers and distributors.

Getting the most from HVAC controls

Because a building's performance can be dramatically improved by installing and fully using HVAC controls, it is essential to understand and correctly use those controls. The place to start is with a close look at what is really transpiring in your building, 24 hours a day, seven days a week.

What is happening with each piece of equipment? On holidays? Weekends? As the seasons change, do your operations change? It is important to understand where and how energy is being consumed in order to identify where waste is occurring and where improvements can be implemented. Then it is imperative to ask, "What exactly do I want these controls to do?"

Energy management systems (EMS) are designed to run individual pieces of equipment more efficiently and to permit integration of equipment, enhancing performance of the system. In a typical EMS, sensors monitor parameters such as air and water temperatures, pressures, humidity levels, flow rates, and power consumption. From those performance points, electrical and mechanical equipment run times and setpoints are controlled.

Seven-day scheduling provides hour-to-hour and day-to-day control of HVAC and lighting systems and can account for holidays and seasonal changes. As the name implies, night temperature setback allows for less cooling in summer and less heating in winter during unoccupied hours.

Optimal start/stop enables the entire system to look ahead several hours and, relative to current conditions, make decisions about how to proceed; this allows the system to ramp up slowly, avoiding morning demand spikes or unnecessary run times.

Peak electrical demand can be controlled by sequencing fans and pumps to start up one by one rather than all at once and by shutting off pieces of HVAC equipment for short periods (up to 30 minutes), which should only minimally affect space temperature. Economizers reduce cooling costs by taking advantage of cool outdoor air. Supply-air temperature-reset can prevent excessive reheat and help reduce chiller load.

An EMS can provide an abundance of information about building performance, but someone has to figure out what they want the EMS to do and then give it directions. Calibrating controls, testing and balancing are key to any well-maintained HVAC system, but are especially critical to optimize control efforts.

Variable speed drives and energy-efficient motors

Variable speed drives (VSDs) are nearly always recommended as a reliable and cost-effective upgrade.

VSDs are profitable where equipment is oversized or frequently operates at part-load conditions. Savings of up to 70 percent can be achieved by installing VSDs on fan motors operating at part-load conditions. They may be applied to compressor or pump motors and are generally used in variable air volume (VAV) systems. They are also cost effective in water-side applications. Backward-inclined and airfoiled fans are the best VSD candidates.

Air-handler configurations controlled by variable inlet vanes or outlet dampers squander energy at part-load conditions. Using throttle valves to reduce flow for smaller pumping loads is also inefficient. The efficiency of motors begins to drop off steeply when they run at less than 75 percent of full load; they can consume over twice as much power as the load requires. VSDs operate electronically and continually adjust motor speed to match load.

The power to run the VSD is proportional to the cube of the speed (or flow), which is why this technology is so efficient. If the speed is reduced by just 10 percent, a 27 percent drop in power consumption should result. A VSD pilot study performed by EPA found that VSD retrofits realized an annual average energy savings of 52 percent, an average demand savings of 27 percent and a 2.5-year simple payback.

Perform harmonic, power factor, electric load, and torsional analyses before selecting a VSD. Though harmonic and power factor problems are not common in VSD applications, VSDs should generally be equipped with integral harmonic filters (or a three-phase AC line reactor) and internal power factor correction capacitors (or a single capacitor on the VSDs' main power line). In general, this equipment is not standard and must be specified.

Improved design and better materials enhance the performance of energy-efficient motors, which use 3 to 8 percent less energy than standard motors; units with efficiencies of 95 percent are available.

To achieve maximum savings, the motor must also be properly matched with its load, increasing run time at peak efficiency. Motors operate best when running at 75 to 100 percent of their fully rated load; motors routinely operating below 60 percent of rated capacity are prime candidates for retrofit. For motors whose loads fluctuate, VSDs should also be considered.

Smaller, more efficient motors are integral to a system downsizing stratagem; downsizing a 75 horsepower standard motor to a 40 horsepower energy-efficient model will result in energy savings of 15 percent.

Some energy-efficient motors have less "slip" than standard-efficiency motors, causing energy-efficient motors to run at slightly higher speeds; consider a larger pulley to compensate for the higher speed and to maximize energy savings. Installing a new pulley or adjusting the existing one can also be an alternative to a VSD when the cost for the VSD is prohibitive or the load has been reduced.

Improving fan system performance

A common way to improve the efficiency of the air distribution system is to convert constant air volume (CAV) systems to VAV. One authority on energy issues, E-Source, reports that "typical (VAV) air flow requirements are only about 60 percent of full CAV flow."

VAVs respond to load requirements by varying the volume of the air through a combination of pressure controls and dampers rather than by varying the air's temperature. According to the air pressure, fan power and volume of conditioned air are reduced, thus increasing energy efficiency. Of course, it is crucial to maintain indoor air quality (IAQ) when altering air handling systems.

To maximize savings, VAV components such as VSDs, variable-pitch fan blades, diffusers, mixers, and VAV boxes must be operating properly; careful zoning is also required to achieve VAV optimization.

E-Source recommends considering the following VAV retrofit procedures:

• complete load reduction measures and calculate the maximum and minimum air flow requirements,


• measure existing fan performance; examine duct system for possible improvements,

• stage fans that are in parallel configurations,

• commission the system thoroughly,

• optimize static pressure setpoint and implement reset control, and

• possibly remove return air fans.

Energy-efficient and properly sized motors are also recommended along with careful control strategies. Installing a self-contained, thermally powered device to each diffuser can add greater control to VAV systems by controlling individual spaces, rather than entire zones, and eliminate the need for VAV boxes. Such a device also offers VAV-style capabilities to CAV systems.

VAV retrofit costs and paybacks can vary widely. Installation problems related to fan control, reduced supply air distribution, location of pressure sensors and their reliability, in addition to deficient design, can diminish a VAV retrofit's performance. Because VAV boxes are relatively expensive and one is required for each zone, it is generally not cost effective to partition the space into many zones. Careful zone designation -- according to occupancy, internal loads and solar gain -- will maximize efficiency, increase comfort and reduce reheat.

When reheat cannot be eliminated, consider these steps to minimize it: ensuring thermostat calibration; increasing supply air temperatures during the cooling season; and monitoring reheat year round and possibly employing reheat only during winter months. Where reheat is used primarily to control humidity, a desiccant wheel or a heat pipe might be considered.

Downsizing existing VAV fan systems is a relatively low-cost way to save energy when loads have been reduced or when the air distribution system was oversized to begin with. The following are means to downsize fans or airflow requirements:

• Reduce static pressure setpoint to meet actual temperature and airflow requirements.

• Rightsize motors and upgrade to energy-efficient models; install larger pulleys.


• Replace the existing fan pulley with a larger one; that will reduce the fan's power requirements by reducing its speed.

• Make sure the fan's speed corresponds to the load. Reducing a fan's speed by 20 percent reduces its energy consumption by approximately 50 percent.

There are several ways to determine if VAV fan systems are oversized. If a motor's measured amperage is 25 percent less than its nameplate rating, it is oversized. If a fan's inlet vanes or outlet dampers are closed more than 20 percent, it is oversized. If the static pressure reading is less than the static pressure setpoint when inlets or dampers are open and VAV boxes open 100 percent, as on a hot summer day, the system is oversized. Again, be sure to consider IAQ requirements when downsizing air handling systems.

Chillers and thermal storage

No one wants to replace a perfectly good chiller just because of the CFC phaseout. But once load-reducing efficiency upgrades have been completed, it may actually be profitable to replace an oversized chiller. That's especially true given rising prices and tightening supplies of CFC refrigerants.

Oversized units 10 years or older are good candidates for replacement. A high-efficiency chiller reduces energy costs throughout its lifetime; initial costs are reduced because the replacement chiller is smaller than the old one. Depending on the old unit's efficiency and load, a high-efficiency chiller's energy consumption can be.15 to.30 kW/ton less, decreasing energy consumption by as much as 85 percent if combined with downsizing.

An alternative to replacement is to retrofit chillers to accommodate a new refrigerant and to match reduced loads. That may involve orifice plate replacement, impeller replacement and possibly compressor replacement, depending on the chiller's specifics.

Retrofitting may entail gasket and seal replacement and motor rewinding. Depending on the refrigerant and the way the retrofit is performed, the chiller may lose either efficiency or capacity. To determine whether replacement or retrofit is a better option, consider both initial and life-cycle costs.

Retubing the condenser and evaporator yields sizable energy savings but whether it makes sense, given its high cost, depends on the condition of the chiller. Water-cooled condensers are generally more efficient than air-cooled units. Because condenser water flows through an open loop, it is susceptible to fouling. Scale build-up will inhibit heat transfer efficiency; maintenance is therefore required to keep the surfaces clean.

Absorption chillers are an alternative to centrifugal models. Absorption chillers cost up to $150 per ton more than vapor compression chillers like centrifugal units, but can be profitable in areas of high electrical demand charges or where steam or gas is available, depending on the local utility rate structures. Using a combination of the two chiller types can reduce electrical demand charges.

Thermal energy storage (TES) uses conventional chiller equipment to produce conditioned water or ice (or occasionally another phase-change material) in off-peak periods. Water is withdrawn from storage during the day or at peak hours and circulated through the cooling system.

TES systems can be incorporated into new and existing systems and can provide partial load leveling or full load shifting. TES helps decrease operating and maintenance costs; in some cases, a smaller chiller can be specified. Some systems provide lower supply air and water temperatures, so air and water flow requirements can be cut.

Water-side improvements

Fill material, size and fan configurations affect cooling tower efficiency. Cellular fill (aka film packing) increases efficiency over other fill types. Oversizing the tower to allow for closer approach to ambient wetbulb temperature can improve its efficiency. Generously sizing the tower and increasing its share of the chiller load can make economic sense because a cooling tower's initial cost and energy use per ton are less than a chiller's.

At part-load conditions, applying a VSD to the fan (or pump) will improve the tower's efficiency. Systems with VSDs and several fans are more efficient when all tower cells are operating at reduced speed as opposed to one or two cells at full speed.

Because cooling towers contain large heat exchange surfaces, fouling -- scale or slime build-up -- can be a problem. The efficiency of improperly treated systems can be improved with effective water treatment. High-efficiency towers are available; induced-draft types are more popular and efficient than forced-draft towers. Performance can also be improved by increasing cooling surface area.

In traditional pumping systems, flow is generally constant volume; a throttle valve reduces flow at part-load conditions, inhibiting efficiency.

Installing VSDs on secondary pumps in variable flow systems, rightsizing pumps and motors to meet load requirements, and upgrading single loop systems to primary/secondary loop configurations can increase the performance and reliability of pumping systems. In upgrading chilled water pumps, it is important to meet maximum and minimum flow rates through the chiller.

Other cooling options

Desiccants are dehumidification materials which can be integrated into HVAC systems to reduce cooling loads and increase chiller efficiency while improving indoor air quality and comfort. Formerly found only in niche and industrial applications, desiccant cooling is extending throughout commercial markets.

Desiccants make sense when the cost to regenerate them is low compared to the cost to dehumidify below dewpoint and can reduce HVAC energy and peak demand by more than 50 percent in some cases.

Evaporative coolers provide one of the most economical and efficient means of cooling, using up to 75 percent less energy than vapor-compression systems. Though initial cost is typically higher, paybacks for evaporative coolers range between six months and five years. Though evaporative coolers are particularly prevalent in the arid West and Southwest, they can service most U.S. climates. E-Source states that, in combination with evaporative cooling, desiccant cooling can eliminate refrigerative air conditioning in many climates.

Hybrid systems that integrate evaporative cooling with conventional HVAC technologies offer additional opportunities. To improve performance consider lower air velocity; better fill materials; higher fan, pump and motor efficiencies, including VSDs; better belts or direct drive; improved housing; improved controls; and duct sealing. Proper maintenance is key to energy-efficiency.

Packaged air-conditioning units are typically found in buildings or building zones where the cooling load is less than 75 tons. Running these units at part load can severely reduce efficiency. They are generally not as efficient as chiller systems but can be upgraded and rightsized when replaced. Existing systems can be improved by using higher efficiency compressors, larger condensers and evaporators, and VSDs, though life expectancies of 10 to 12 years for these technologies may mean that retrofits are not cost-effective.

Heat pumps are among the most energy-efficient heating and cooling technologies available today. Low operating costs, increased reliability and long life expectancies improve their viability. They function best in moderate climates and proper sizing is critical.

Multi-unit configurations can service larger loads and provide zoning; large, modernized central units offering capacities of up to 1000 horsepower or 750 kilowatts are gaining popularity. Air-to-air type heat pumps are the most common because of low up-front costs; ground supply heat pumps are the most efficient but tend to have higher initial costs.

Boiler upgrades

Especially in colder climates, improved boiler performance -- with improved fuel and airflow controls over a range of load conditions and increased heat transfer surface areas -- can contribute substantially to energy savings. Smaller units arranged in modular systems increase efficiency up to 85 percent while small units replacing those with open-loop condensing systems shoot combustion efficiency up to 95 percent.

Boiler retrofits, combined with improved maintenance measures, can also increase efficiency -- up to 90 percent. New burners, baffle inserts, combustion controls, warm-weather controls, economizers, blowdown heat recovery and condensate return conversions provide increased efficiency opportunities. A smaller "summer" boiler might be a good option when a boiler is required year round though at reduced capacities in warmer conditions. The much smaller summer boiler is sized for reduced loads; the main boiler is shut down.

HVAC upgrades can provide tremendous economic benefits, improve occupant comfort and system reliability, and reduce operating costs. But to maximize benefits and minimize capital investment, load-reducing measures, such as lighting upgrades, should precede HVAC system upgrades.