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Home > Issue by Date > April 2008

Net-Zero-Energy Buildings

Can these types of facilities be market viable by 2030?

By Kent Peterson, P.E.

With increasing energy costs and climate change considerations, design guidance related to energy efficiency is more important than ever. Nowhere is this more evident than in this industry, given that buildings consume roughly 40% of the primary energy in the United States, according to the U.S. Energy Information Administration (EIA).

Additionally, the EIA has reported that world energy consumption is projected to grow by approximately 60% from 2004 to 2030. And while energy consumption and prices continue to rise, the true costs are even higher when considering the impact on future generations and the environment.

In the past, the building industry has focused on minimum energy efficiency requirements to reduce consumption. Recognizing that more must be done, the industry must look ahead to energy optimization and provide guidance that will result in market viable net-zero-energy and carbon neutral buildings. This transformation will change the way facilities are designed, built, and operated.

As one of several groups striving for energy neutral buildings, the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) is working toward this change. The Society has publicly stated its vision to improve building energy performance continuously, with the ultimate goal of market viable net-zero-energy buildings by the year 2030.

ASHRAE defines net-zero-energy buildings as those which, on an annual basis, use no more energy from the utility grid than is provided by on-site renewable sources. These buildings use 50% to 70% less energy than comparable traditional counterparts. The remaining energy use is derived from renewable sources, such as solar panels 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.

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Traditional design would be to meet the U.S. model energy code, based on the ASHRAE/IESNA Standard 90.1 for energy conservation in commercial buildings. But in this new age of energy optimization, a project team may want to set out to design a net-zero-energy facility, which would surpass the traditional design in terms of energy savings.

By orienting the building on the site properly, designers can save energy by optimizing natural daylighting, gaining passive solar heat in winter, and minimizing solar heat gain through windows. Other building envelope measures could include increasing mass and R-value of walls and roofs with enhanced insulation, exterior shading, skylights, and optimized surface reflectance.

All of those measures, which involve existing technology, bring the building closer to net-zero on the energy scale. These measures can also lower the requirements of the environmental control systems used, thus reducing the size and cost of mechanical and electrical systems.

Next, HVAC, service water heating, and lighting measures would be added to the design. Again, all existing technologies can be used here: high efficiency lighting with occupancy sensors and daylighting controls (which lower lighting energy and cooling requirements); heat recovery systems; high efficiency water heating systems; and ventilation approaches that maximize outside air when temperatures are mild.

Other measures include controlling the amount of outside air that needs to be conditioned (through demand control ventilation strategies); adding technologies such as ground source heat pumps (to improve HVAC efficiency); reducing energy at part loads through variable speed air conditioners, fans, and pumps; and providing training on energy efficient building operation.

Implementing these strategies puts the project even closer to the goal of net-zero-energy. The facility should be able to save roughly 50% to 70% on annual consumption with advanced efficiency measures. Renewable sources can generate enough power to offset the remaining annual energy needed for operation. An example of this scenario can be viewed in a video 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 of best practices to apply to the design, construction, and operation of low- 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 load factors.

Whole building design or integrated building design (IBD) are collaborative processes that can help achieve high performance, low energy buildings by considering all design variables. IBD looks at how the building and its systems can be integrated with supporting systems on its site and in its community and at how materials, systems, and products of a building connect, interact, and affect 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 buildings more efficient, fms can help set annual goals and relate their experience to designers on how the systems work together, which is key to better sustainable design.

Achieving net-zero-energy in today’s facilities requires careful IBD. Fms should strive to squeeze as much efficiency out of their buildings before implementing the more costly renewable strategies. The cost-effectiveness of net-zero-energy facilities will improve as the costs for energy and carbon emissions increase and the prices of renewable technologies are reduced.

With rising energy costs and climate concerns, the time has come for more collaborative 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 saying no longer holds meaning regarding energy use in the building industry.

Peterson, P.E., fellow ASHRAE, is the 2007-08 president of ASHRAE and vice president and chief engineer of P2S Engineering Inc., a consulting engineering 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 avazquez@groupc.com.

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