Designing office space: HVAC systems
Office building clients demand sustainability, flexibility, and cost conservation in both new and existing buildings.
Michael F. Cooper, PE, LEED AP, Managing Principal, Harley Ellis Devereaux, Southfield, Mich.
Kurt Karnatz, PE, CEM, LEED AP, HBDP, HFDP, President, Environmental Systems Design Inc., Chicago
Kent W. Peterson, PE, FASHRAE, LEED AP BD+C, BEAP, Vice President/Chief Engineer, P2S Engineering Inc., Long Beach, Calif.
CSE: What unique requirements do office building HVAC systems have that you wouldn’t encounter on other structures?
Peterson: One unique requirement of an office building is the flexibility requirement of the building HVAC system to be reconfigured four or five times over the life of the system.
Karnatz: The need to support multiple and diverse occupancy needs is the most common difference between other types of buildings.
Cooper: Office building systems have more diversity in occupancy schedules, required ventilation rates, and functionality. Available equipment space is consistently being challenged to yield higher net to gross square footage. Engineered systems want to be high efficiency, but also with reasonable initial cost. Finally, office buildings are driving simplicity of design. Limited building management resources are encouraging the design community to look at sophisticated systems to meet the functional needs, which are easy to monitor and control.
CSE: How can automated features and remote system control benefit office building clients?
Karnatz: Remote monitoring is certainly becoming a very important part of lean building operations and management and will continue to grow. Remote oversight of building system operation provides an opportunity to continuously monitor and respond to load and system changes. It can provide predictive and preemptive information to better respond to the operational and maintenance needs of a system.
Cooper: When building management resources are limited, automation and remote control are keys to making these facilities run. Through Web-based management systems, building occupants can provide input on system performance and, likewise building management who may be responsible for multiple facilities can respond immediately to system notifications and tenant requests. The result is improved responsiveness and a more satisfied tenant community.
Peterson: Office buildings experience a wide range of occupant diversity throughout the day. Today’s HVAC and lighting controls have the capability of reducing lighting levels when daylight is available or turning off lights when rooms are not occupied. This can result in 50% less lighting energy on an annual basis.
CSE: What is the most important indoor air quality (IAQ) issue you typically address in these projects, and how do you address it?
Cooper: Ventilation rates, with varying occupancy and space function, is one of the key issues we see on our projects. In high-density spaces requiring large amounts of ventilation air, dedicated outside air units used in conjunction with energy recovery wheels and demand-controlled ventilation help offset energy consumption. Underfloor displacement air delivery systems are an effective way to get just the right amount of ventilation air where and when you need it. Understanding how fresh air is introduced into the building and managing the quality of the outdoor air through appropriate filtration systems is essential. MERV-13 or better filters are typically utilized for this purpose, with positive results.
Peterson: The most important IAQ issue is to provide the proper amount of ventilation air throughout the range of operation of the building. We always provide airflow measurement of the outside air with demand-controlled ventilation in densely occupied spaces to optimize IAQ and energy efficiency for the building.
Karnatz: Occupant comfort is enhanced in environments that feel vibrant and fresh. Today’s systems that support higher air change rates and lower thermal asymmetry are able to deliver consistent indoor air quality, thermal comfort, and occupant satisfaction.