Buildings Operating Under Their Own Power

“LEED certified building” is a common phrase these days and has quickly become a part of Oregon’s vernacular. However, less common is the phrase “net zero energy building,” likely because building a structure with net zero energy consumption and zero carbon emissions is even more difficult than building a LEED certified structure.

“Net-zero energy building” or “zero energy building (ZEB)” is a general term applied to a building which has zero net energy consumption and zero net carbon emissions annually (excluding energy and emissions generated from the construction of the building). This means that every year, net-zero energy buildings produce as much energy as they use—they are the poster-child of energy efficiency.

Net-zero energy buildings are also carbon neutral because they don’t use fossil fuels in their operation or create direct greenhouse gases. This gives them a much lower overall ecological impact than other “green” buildings, because many green buildings still require a significant amount of fossil fuel production to power and heat the building. Green building certifications do not require a building to have net zero energy and emissions productions; some certifications only require the building to reduce energy use to a few percentage points below the average. Most green certification programs, including LEED, simply look at building energy output and do not address building design.

How Do Zero Energy Buildings Work?

Much of a net-zero energy building’s efficiency comes from its initial design. Net-zero energy buildings are designed to take advantage of sunlight and solar heat through the use of skylights and solar tubes for lighting and warming purposes. They are also built to take advantage of prevailing breezes and shade for natural ventilation and cooling. Net-zero energy buildings often have vegetation on their rooftops for heat insulation in the winter and cooling in the summer.

Net-zero energy buildings also reduce heating and cooling loads by using high-efficiency equipment and windows, using sheltered-building principles and shade sensitive landscaping, adding insulation, and taking advantage of natural ventilation. Further, many net-zero energy buildings use water conservation fixtures, heat recovery units on waster water, and solar water heating.

They are also designed to reclaim energy from other sources that would normally get wasted including: refrigerator exhaust, energy from computer servers and office equipment, and even human body warmth. Nighttime lighting is typically done through fluorescent and LED lighting, which use one-third less power than incandescent bulbs, while also not producing unwanted excess heat.

Most net-zero energy buildings are still connected to the general energy grid due to traditionally significant fluctuations in their energy supply. While many net-zero energy buildings produce energy onsite, it is usually not enough to continually power the entire building. Therefore, most net-zero energy buildings employ a mixed strategy of energy conservation and production to achieve net zero status.

Advantages of net-zero energy buildings
*  Reduced energy costs due to increased efficiency
*  Protection for building owners from future energy price increases
*  Improved reliability of energy availability
*  High resale value of building as demand for net-zero energy buildings currently exceeds supply
*  Avoidance of expensive retrofits if emissions-regulating legislation is passed
*  Passive solar design (relies mostly on sunlight/shade to maintain comfortable internal temperatures rather than active heating/cooling systems) has demonstrated energy consumption reductions of 70% to 90% in many locations

Disadvantages of net-zero energy buildings
*  Initial construction cost can be higher than other buildings
*  Currently, few designers have the skills or experience to build net-zero energy buildings
*  Climate specific design may make it difficult/expensive to respond to changing climate conditions caused by global warming

Green Building Policies

From 2008 to 2012, the U.S. Department of Energy plans to award $40 million to a variety of Building America teams, academic, and building industry leaders to develop net zero energy homes that consume 50%-70% less energy than conventional homes. States and municipalities have also begun to adopt policies which incent or require green building practices.

At the state level, the Oregon legislature passed SB 79 this session, which mandates that the state building code be amended to match building energy efficiency at the national model codes’ level and creates a “Reach Code” of optional construction standards that achieve greater energy efficiency than what is required by the state building code. The changes in the state code are estimated to make nonresidential buildings 15 – 25% more energy efficient and residential buildings 10 – 15% more efficient, compared to building energy efficiency under the current code.

In Texas, municipally-owned Austin Energy is spearheading an initiative to amend city building codes to make all new single-family homes zero energy capable by 2015. Other amendments to the codes will require radiant barrier and duct testing, making homes 65% more efficient than required under current codes.

Requiring that new residential buildings be net-zero energy buildings makes Austin’s city building code the most ambitious green building policy yet. Oregon may not be ready for so large a step, but policy makers should not be satisfied with the smaller steps they have taken. The state’s “Reach Code” and other local efforts should be viewed as pilots—merely policy trials to discover problems and develop ‘best practices’ before fully implementing the higher goal of energy neutral buildings.

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