One way to identify tenant needs in existing buildings is to note what architects and designers are trying to create for clients in new buildings. The objective for a new building is to provide the ideal office space. Tenants are often looking for space that can address such issues as flexibility, modular space planning, environmental considerations and individual temperature comfort. A particular hot spot for many national tenants is to gain the highest level of productivity from their employees. This usually means the building will need plenty of HVAC zones, flexible office hours and point-of-use supplemental systems. These factors point to a flexible and often programmable HVAC system that can meet tenants' needs.
Architectural trends can also create new loads and requirements for an HVAC system in an existing facility. More natural light can increase heat loads; atrium designs can obstruct air distribution; additional zones can increase the overall volume of ventilated air needed, the quantity of heat to be rejected and the amount of outdoor air required. If a building doesn't have a flexible HVAC plant, then modifications or upgrades to the HVAC system will be necessary to compete with new building design and technology.
One factor that must be considered in any analysis of a possible retrofit is that an HVAC upgrade usually means that the building has to be brought into compliance with current codes. Some codes are based on prescriptive regulations; however, the trend to create a safer and healthier indoor environment can also bring new performance requirements. For example, over time, the percentage of outdoor air has gradually been increased, and current requirements may call for more outdoor air than many buildings have the capacity to condition. Bringing the building up to code may require a significant investment in upgrades beyond those originally planned.
Making Retrofit Decisions
HVAC systems are major energy users, and new HVAC technology is far more efficient than 15 to 20-year-old systems in place in buildings. In some cases, the energy savings alone are so substantial that they justify the upgrade investment. But in many commercial office buildings it can be difficult to justify an HVAC upgrade. Perhaps some upgrades have been performed over the years, reducing the energy savings now available. Or perhaps the owner has a too short a payback-period requirement for energy upgrades.
When energy savings alone do not clearly justify an upgrade, how does the facility executive responsible for a commercial office building determine whether and how to upgrade the HVAC system? It is best to start with the building profile. A relatively small or mid-sized building (less than 200,000 square feet) may present marketing opportunities not available to larger facilities. For instance, instead of converting a constant-volume system to variable-air-volume (VAV), it might be possible to make each floor a separate zone. The marketing plan could then be changed to focus on larger, whole-floor users with large bullpen work areas that do not require multi-zone improvements.
In a medium or large-sized building, upgrade options will depend more on the type of system already in place. If the base building system is a constant volume system, with the main fans delivering varied air temperatures to large sectors of the building, there isn't much choice. To serve the varied needs of today's tenants, the facility executive will need, at a minimum, to increase the zoning abilities. How this is accomplished depends on the building's design and business plan.
For example, new speculative office buildings sometimes install heat pumps, which can deliver heating or cooling to small or large zones, are easily programmable, and operate at about 50 cents a ton per hour. But is the first cost for installing heat pumps a good value for retrofits? Probably not if the building was configured as a constant-volume or multi-zone system. Using heat pumps would require running condenser piping throughout the building and changing the fresh air distribution; what's more, the actual conversion could not run parallel to the old system if this retrofit was attempted in the summer because the cooling tower would be reused.
In this case, options for conversion should be limited to a VAV conversion or to individual zone diffusing that does not reduce energy costs but does create comfort zones similar to VAV systems. VAV systems provide a constant temperature to the space, but the air volume varies with the comfort setting. If the building was constructed after 1975, it probably has some type of VAV system installed. The earlier systems did provide easy zone creation; however, after-hour and flexible operation were usually not part of the operating system.
The most difficult VAV retrofit decisions are the ones where the payback related to energy reduction has already been captured by vortex dampers or by the later addition of variable frequency drives. If the facility will not receive an initial influx of energy savings, HVAC retrofits will have to be justified based on increased flexibility, after-hour operation and supplemental cooling. The facility executive must spend the time necessary to understand the overall value to the asset from a marketing standpoint.
It is important that all values are considered when making the decision. More is involved than just the cost of energy. There will be other gains that are not so obvious. A new cooling tower or new chiller not only operates with less kilowatts per ton, it also has new heat transfer surfaces, better part-load abilities and generally reduces maintenance requirements. The amount of labor and maintenance required to service a temperamental HVAC system can be quite a surprise once it is segregated from general operating costs.
The facility executive must also look at the useful life of the existing system. Will there be parts available next year? Is there a service company that will be willing to support the system? If a decision is made to sell the building will the system be flagged as unserviceable? Can the system still be used when a big block of space comes up in two years? These are all questions to ask when a system is facing obsolescence and when reliability of building systems becomes a factor in the marketplace.
There are other building details that sophisticated tenants are aware of or will become aware of if they enlist a good tenant representative or broker. Consider a broker with a client that is considering an existing building over the brand-new building across the street. The potential tenant is concerned with the condition of the HVAC system and requests the following information:
• Is the ductwork and distribution system clean? Please offer some verification.
• How is the insulation attached? Is it interior or exterior fiberglass?
• Is sound batting provided?
• What is the zoning per terminal?
• What are the temperature setpoints of the zones? How many zones are in my space?
• What is the noise level of the terminals?
• Can we control the perimeter zones of the offices separately?
• Is there any asbestos on the HVAC system, piping or ceiling?
• How can I operate after hours and what is the cost per hour?
• If I want to add some additional servers, is there a tenant tower for condenser water?
• What are the watts per square foot and the cubic feet per minute of ventilation air?
• What am I guaranteed in the future?
• How will I be billed for use of my after-hour heating and cooling?
In the last few years, tenants have been even more concerned with the office IAQ (Indoor air quality) environment. The more important the staff is to the operation, the more concern for the users' welfare. Tenants are asking more questions like these:
• What is the outside air ratio?
• Where does the outside air for my area originate and can you achieve 100 percent economizing?
• Do you have a proactive plan for indoor air quality complaints?
• Do you allow smoking?
• Do you have pressurization, smoke tower, stairway pressurization or smoke exhaust system?
• Are there any negative air situations in this building and does any of the air come from infiltration?
• Is there any redundancy to the heating and cooling systems?
• What is the origin, quality and reliability of the electrical service supplying the building HVAC system?
Competing for Tenants
Potential tenants may also want to see the property's preventive/predictive maintenance program, or to review the energy or computerized maintenance program to determine what occurs when the building operates outside its design parameters. This is when a facility executive must know the market. Can the property afford not to retrofit? Very often an energy payback exercise will show the project being way off the owner's target. But the analysis must also take into account lease-up value, tenant retention, cash flow and ultimately overall asset value. If a property is competing with a state-of-the-art VAV building with lower operating costs and greater flexibility, where are the tenants most likely to go?
In a landlord's market, a building with an outdated HVAC system may do all right. In a tight market, with a lot of available space, that property may either have to reduce rent, offer concessions or decide to give tenants what they really want: An HVAC system that is flexible, usable, efficient and able to provide comfort and good indoor air quality for employees.
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.
