Intro
One of facilities managers’ greatest operational challenges is dealing with service calls from building occupants. Legitimate calls must be responded to and resolved in a timely way-if the mechanical system is down, a technician should be dispatched quickly to investigate. On the other hand, illegitimate calls should be discovered quickly, or better yet, prevented in the first place-if only one person out of the 20 people working in a cooling zone is uncomfortable, and if the zone temperature and humidity are where they should be, then the facility manager can’t do much to improve the situation because most HVAC systems simply aren’t designed to allow for highly localized control of space conditions. How can these calls be prevented?
And it’s not just a question of occupant comfort. Anytime a system is running when it doesn’t need to be, energy is being wasted, hurting both the environment and your O&M budget. Many occupants will do the right thing and turn systems off when they’re not needed as long as the building makes it easy for them. If there’s no obvious way to turn the system off, it usually gets left on. In any building without automated controls, the result is unnecessary system operation and needlessly high utility and maintenance bills.
An emerging green building strategy offers a great solution: localized individual space controls. This topic is an excellent example of a green building strategy that is also a high-performance building strategy. In other words, why wouldn’t anyone consider it?
Occupant Control-Standard Practice
Buildings employ an endless variety of controls on their mechanical systems, with a wide range of possible occupant influence. Small buildings may have separate heating & cooling units in each room, and these may have automatic thermostatic control, manual control, on/off control only, or even no control. Larger buildings typically use central systems with central control, and while some systems allow occupants to adjust the zone thermostat, such adjustments may have limited or no effect on actual system operation.
Lighting systems typically offer a greater level of occupant control in the sense that occupants can usually turn the lights on or off, but for large spaces the switching often regulates whole banks of lights rather than individual fixtures or small groups of fixtures. Moreover, except for certain applications such as conference rooms, lights must be fully on or fully off – dimming capability is rarely offered.
Ventilation systems consistently offer occupants far less control than heating, cooling, or lighting. Except for applications having dedicated local exhaust fans (kitchens, bathrooms), occupants virtually never have a way to get more fresh air into their space from the mechanical system if they want it. Their only recourse is to open the windows if they can, which may cause its own problems (e.g., higher HVAC bills).
Why More Occupant Control can be Better
Recent articles in this series have stressed the importance of maintaining a healthy, comfortable working environment for building occupants. This means ensuring the space has a comfortable temperature, humidity, and air speed; adequate ventilation air; and adequate lighting. None of these criteria are purely objective because of varying personal preferences among the occupants, so traditionally buildings are designed to meet the applicable industry standards, e.g., for thermal comfort and ventilation.
But facilities managers know that operating the building to meet the standards doesn’t necessarily keep every occupant happy all the time. The standards designers agree, often stating outright that their intention is to publish guidelines for uniform conditions that will keep most of the people happy, most of the time. Indeed, this is the best you can expect under these assumptions. However, innovative building designers and operators recognize that they needn’t be restricted to uniformly operated systems. They can take the notion of “zoning” the HVAC and “banking” the lights down to a finer level of detail, offering individual occupants at least partial control over the conditions in their space.
Individual control keeps occupants more satisfied and productive by allowing them to tailor the space conditions in two important ways: 1) to suit their personal preferences, which may well be outside the “average” ranges published in industry standards, and 2) to suit changing conditions in the space caused by weather, occupancy, equipment loads, etc. Although providing individual control may cost some money up front, the payback rule applies because they can save on both energy bills and maintenance bills.
The clearest example of reduced O&M costs may be for lighting. First, the University of California, Berkeley’s Center for the Built Environment has shown that building occupants use 40% less lighting energy when given convenient individual control of lights. Since lighting is one of the biggest energy loads in many buildings, that quickly adds up to real savings. Second, lighting controls can also extend the calendar life of the lamps, thereby creating a longer interval between lamp replacements and therefore savings on maintenance materials and labor costs.
Individual Controls and LEED-EB
Many existing buildings were designed as sealed environments with no occupant controls and no physical connection to the building grounds and neighboring areas. Such an environment can result in the occupant discomfort mentioned above, as well as a lack of connection to the outdoors. The LEED for Existing Buildings Rating System provides incentives to improve this situation by rewarding provision of individual controls in two credits:
- Environmental Quality credit 6.1: Controllability of Systems—Lighting
- Environmental Quality credit 6.2: Controllability of Systems—Temperature and Ventilation
Credit 6.1 requires that at least 50% of building occupants have individual lighting controls, while credit 6.2 requires that at least 50% of building occupants have individual temperature and ventilation controls. For credit 6.2 operable windows may be used instead of mechanical system controls for spaces near the windows. Both credits give separate consideration for individual workspaces and multi-occupant group spaces.
By providing individual controls such as light switches, thermostats, vents, operable windows (where available) and shading devices, building occupants can customize the indoor environment, making them more satisfied and productive. This is part of what green building and high-performance building operations is all about.
Conclusion
The past few articles in this series have been all about the occupants: keeping them comfortable, keeping them healthy, and giving them some control over their space conditions. Fundamentally, the reason the building exists in the first place is to provide a safe, efficient working or living environment for the occupants. Good facilities managers will take the time to give proper focus to occupants’ needs in these areas, both for the occupants’ sake and for their own sake: keeping occupants happier will often save money and reduce operations hassle. What facility manager would say no to that? Resources
U.S. Green Building Council (www.usgbc.org)
The USGBC’s LEED for Existing Buildings program addresses thermal comfort in several of its requirements and credits.
University of California—Berkeley. College of Environmental Design, Center for the Built Environment. (www.cbe.berkeley.edu/research/wireless_lighting.htm)
Development of a Prototype Wireless Lighting Control System 2002. 11 February 2005. Efficiency data is from a pilot installation of the lighting control prototype. CBE is expanding research in this area.
