The HVAC Factor: Net-Zero-Energy Buildings
By Kent Peterson, P.E.
Published in the April 2008 issue of Today's Facility Manager
Withincreasing energy costs and climate change considerations, designguidance related to energy efficiency is more important than ever.Nowhere is this more evident than in this industry, given thatbuildings consume roughly 40% of the primary energy in the UnitedStates, according to the U.S. Energy Information Administration (EIA).
Additionally,the EIA has reported that world energy consumption is projected to growby approximately 60% from 2004 to 2030. And while energy consumptionand prices continue to rise, the true costs are even higher whenconsidering the impact on future generations and the environment.
Inthe past, the building industry has focused on minimum energyefficiency requirements to reduce consumption. Recognizing that moremust be done, the industry must look ahead to energy optimization andprovide guidance that will result in market viable net-zero-energy andcarbon neutral buildings. This transformation will change the wayfacilities are designed, built, and operated.
As one ofseveral groups striving for energy neutral buildings, the AmericanSociety of Heating, Refrigerating and Air-Conditioning Engineers(ASHRAE) is working toward this change. The Society has publicly statedits vision to improve building energy performance continuously, withthe ultimate goal of market viable net-zero-energy buildings by theyear 2030.
ASHRAE defines net-zero-energy buildings as thosewhich, on an annual basis, use no more energy from the utility gridthan is provided by on-site renewable sources. These buildings use 50%to 70% less energy than comparable traditional counterparts. Theremaining energy use is derived from renewable sources, such as solarpanels or wind turbines located at the facility.
To envision this, it may be helpful to walk through the design of a new two story office building.
Traditionaldesign would be to meet the U.S. model energy code, based on theASHRAE/IESNA Standard 90.1 for energy conservation in commercialbuildings. But in this new age of energy optimization, a project teammay want to set out to design a net-zero-energy facility, which wouldsurpass the traditional design in terms of energy savings.
Byorienting the building on the site properly, designers can save energyby optimizing natural daylighting, gaining passive solar heat inwinter, and minimizing solar heat gain through windows. Other buildingenvelope measures could include increasing mass and R-value of wallsand roofs with enhanced insulation, exterior shading, skylights, andoptimized surface reflectance.
All of those measures, whichinvolve existing technology, bring the building closer to net-zero onthe energy scale. These measures can also lower the requirements of theenvironmental control systems used, thus reducing the size and cost ofmechanical and electrical systems.
Next, HVAC, service waterheating, and lighting measures would be added to the design. Again, allexisting technologies can be used here: high efficiency lighting withoccupancy sensors and daylighting controls (which lower lighting energyand cooling requirements); heat recovery systems; high efficiency waterheating systems; and ventilation approaches that maximize outside airwhen temperatures are mild.
Other measures include controllingthe amount of outside air that needs to be conditioned (through demandcontrol ventilation strategies); adding technologies such as groundsource heat pumps (to improve HVAC efficiency); reducing energy at partloads through variable speed air conditioners, fans, and pumps; andproviding training on energy efficient building operation.
Implementingthese strategies puts the project even closer to the goal ofnet-zero-energy. The facility should be able to save roughly 50% to 70%on annual consumption with advanced efficiency measures. Renewablesources can generate enough power to offset the remaining annual energyneeded for operation. An example of this scenario can be viewed in avideo available from the ASHRAE Web site at www.ashrae.org/peterson(“Video On Achieving Net-Zero Energy Design”).
The U.S.National Renewable Energy Laboratory (NREL) has determined a set ofbest practices to apply to the design, construction, and operation oflow- and zero-energy buildings. These practices include using:
- Whole building design processes;
- Post-occupancy performance evaluations;
- Measurement procedures;
- Integrated daylighting into the envelope and lighting systems;
- Evaporative cooling systems in dry climates;
- Natural ventilation systems; and
- Demand responsive controls to integrate on-site storage, daylighting,and energy production to reduce peak demand charges and increase loadfactors.
Whole building design or integrated building design(IBD) are collaborative processes that can help achieve highperformance, low energy buildings by considering all design variables.IBD looks at how the building and its systems can be integrated withsupporting systems on its site and in its community and at howmaterials, systems, and products of a building connect, interact, andaffect one another.
This is where fms are critical.Traditionally, fms have had to maintain systems that they inherited,without input into design. Particularly, to make existing buildingsmore efficient, fms can help set annual goals and relate theirexperience to designers on how the systems work together, which is keyto better sustainable design.
Achieving net-zero-energy intoday’s facilities requires careful IBD. Fms should strive to squeezeas much efficiency out of their buildings before implementing the morecostly renewable strategies. The cost-effectiveness of net-zero-energyfacilities will improve as the costs for energy and carbon emissionsincrease and the prices of renewable technologies are reduced.
Withrising energy costs and climate concerns, the time has come for morecollaborative and innovative designs that draw upon the skills of fms.As the saying goes, the best laid plans of mice and men often go awry.With its push for guidance, ASHRAE is striving to make sure that sayingno longer holds meaning regarding energy use in the building industry.
Peterson,P.E., fellow ASHRAE, is the 2007-08 president of ASHRAE and vicepresident and chief engineer of P2S Engineering Inc., a consultingengineering firm in Long Beach, CA. To learn more, visit www.ashrae.org.
What challenges do you foresee for net-zero-energy? Send an e-mail to email@example.com.
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