HVAC Improvements For Existing Buildings – HVAC Retrofits
One way to identify Heating Contractor 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.