Andrew Simpson
by Andrew P. Simpson
Fortunately, a growing trend in the architecture, engineering, and construction industry has been the drive toward net zero building energy use. Typically considered too energy-intensive with high equipment and ventilation needs, life science facilities have often been overlooked for net zero consideration. A combination of many new and existing technologies, however, can be utilized in reducing energy consumption and therefore allow us to achieve net zero in a responsible manner.
The architectural design approach and specific features can play an important role in reducing overall energy use. Thermal mass construction has been used for centuries to absorb energy during peak times and release that energy later in the day, leveling off the peaks and valleys of building load. New glazing technologies offer additional energy savings. Electro- and thermo-chromatic glasses react to electrical current and temperature changes respectively to change the tinting of exterior glazing. A number of mechanical system approaches can be incorporated into the architecture of the building, some of which are described below. Even the way the building program is laid out can affect the energy use. Concentrating similar program types together can allow the mechanical systems to be optimized, with separate, dedicated systems for office space and lab space.
Electrical design focuses primarily on reducing plug loads and lighting demand. The first step is the open discussion with the project team on targeted design criteria for plug loads and lighting power densities. The first step in reducing plug loads is an analysis of what equipment is actually required in the building and eliminating any redundant or unnecessary items. Connected load can be further reduced through the use of automatic receptacles, which turn off during unoccupied periods or when equipment is not in use. Cloud computing can also reduce building energy use by relocating computer power offsite where server energy is used more efficiently. Day-lighting of the building is important in reducing electrical lighting demand. As much of the building as possible should be day-lit with the help of light louvers at exterior windows and light-colored or reflective surfaces indoors.
Mechanical systems are often the largest users of energy in life science buildings, since the systems respond to the building ventilation, heating, and cooling demands. In order to achieve net zero performance, a number of strategies should be developed. Once the building loads are reduced/optimized, the most energy-efficient systems and equipment need be applied. Wherever possible, hydronic heating and cooling should be used, taking advantage of the superior heat transfer characteristics of water over air. This would include water-cooled laboratory equipment over conventional air-cooled units. Geothermal heat pumps can be utilized, where site conditions allow; extensive use of radiant heating and cooling is also recommended. Radiant systems can be provided via panels or sails, as well as through the structural slab.
Reducing ventilation and air conditioning requirements is crucial to lowering energy use. Every effort should be made to reduce airflow to the minimum allowed by code. This can be accomplished through the use of filtered fume hoods, an air quality sensing system, and unoccupied air change rate setback. Strategies to reduce the need for conditioning air include automatic operable windows that open when outdoor air conditions allow, and a nighttime purge, which pulls in untreated outdoor air during cool summer nights to pre-cool the space prior to warmer daytime conditions. Pretreating outdoor air through exhaust air heat recovery is an essential part of the system.
Passive pretreating methods should also be considered. A long, circuitous concrete crawl space or interstitial level can be used as an air intake plenum. The concrete will act as thermal storage, drawing energy out of the air during peak times and returning it during off-peak hours. A transpired solar collector uses a perforated metal panel to create a plenum space at the building exterior that is heated by the sun and is especially useful in colder climates. Natural ventilation should never be overlooked, but needs to assessed in context of the space program, location, and culture of the occupants to enhance that occupant safety and the scientific research is not put at risk.
One last consideration, which is often overlooked, is building occupant behavior. As much as 30% of building energy performance can be attributed to how the space is utilized. Occupant education is an important tool and should be used in conjunction with interactive energy-use meters and displays.
All of the strategies described above have been successfully used on past projects to significantly reduce energy use and consumption. Finding the best combination for each specific life science building program and location can push the industry toward net zero goals and overall success. It’s important to remember that any building can be net zero; it just takes the right attitude, approach, and leadership.
Andrew P. Simpson, PE LEED AP, is an associate at Vanderweil Engineers in Boston.
