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The Future of Energy Efficiency: Net Zero Energy Buildings

February 21, 2012 | 1 comment

Increasing energy efficiency is a goal for almost every building owner and facility manager. But what if a building could actually become completely energy self-sufficient? That’s the idea behind Net Zero Energy Buildings (NZEBs).

The NZEB Commercial Building Initiative (CBI) was developed by the U.S. Department of Energy (DOE) in response to the Energy Independence and Technologies Security Act of 2007. According to the DOE, commercial buildings account for 20% of energy used in theU.S. The goal of the CBIi s to utilize public/private partnerships to achieve marketable high performance, Net Zero Energy Buildings by 2025.

These buildings are already quickly becoming a reality due to advances in retrofit products, construction, renewable energy systems and academic research.

NZEBs are designed to generate as much energy as they consume during the course of one year. This can be achieved by using both supply-side and demand-side renewable energy technologies – both of which a building needs in order to be classified as an NZEB by the CBI.

The power used to operate a NZEB will ideally be inexpensive, locally available, and emissions-free, supply-side, renewable energies – such as the energy generated from photovoltaic panels, solar hot water, wind, hydroelectric technology and biofuels.

On the demand side, energy-efficient retrofits using renewable energy technologies can greatly reduce energy consumption by existing buildings. Some retrofits can even save enough on energy costs to pay for themselves. Retrofits to consider include:

  • Using Light-Colored Roofing Materials – White rooftops reflect about 84% of sunlight, while black rooftops absorb nearly 95% of the sunlight that hits it. Painting roofing surfaces white can potentially save buildings with large roof areas around 10 to 20% on energy bills.
  • Installing window film – Installing high-performance window film helps reduce solar heat gain up to 84%. New generation low-emissivity (low-e) window films help improve insulating properties of single-pane glass to that of dual-pan glass, helping reduce heating costs. Reductions in total energy costs for the average building are 5-15%.
  • Upgrading to efficient lighting Upgrading to an ENERGYSTAR qualified high-efficiency lighting system can reduce heat output by 75% and drastically cut the energy consumption of both the lighting and HVAC systems.
  • Adding an Energy Recovery Ventilation System (ERV) – An ERV system uses recovered energy from building exhaust air to pre-condition fresh outdoor air to the correct temperature and humidity – reducing the workload of the HVAC system. In fact, the need for energy to treat outdoor air can be reduced dramatically – by up to 80% – a savings that can pay for the HVAC system to be downsized.

Other measures to consider include daylighting, water conservation, window shading with awnings and plants, passive solar heating, and insulation among many others.

Not only are NZEBs good for the environment and good for the bottom line, these buildings typically have improved reliability, increased value, and, due to the innovative technologies used, they can actually improve the comfort level of building inhabitants. The DOE CBI Website provides more information on improving energy efficiency with the goal of helping buildings achieve a Net Zero status.

1 Comment

  1. Soumyajit
    March 2, 2012

    Hi Ted,Nicely written! I’m lokoing forward to the book.I agree that increasing insulation in our buildings is a huge step to saving resources and reducing the environmental impact of excessive burning of fossil fuels. But I think as an industry we need to emphasize that the solution is not only about increasing the amount of insulation in the building envelope. I am frequently confronted by clients that insist on R40 or better roofs and walls, but then they want to plaster their northern elevation with glass to capture the view, or they are lokoing for the cheapest installer for their highly insulated wall and roof systems. While the high r-value walls and roofs do have a significant impact on the performance of these buildings, I suggest their first dollars are better spent on energy efficient windows, better design, and a tighter envelope.I would suggest that the lowest hanging easily accessible fruit is air infiltration. No matter how well insulated your wall or roof, what good is it if the cold air is simply making an end run and infiltrating your envelope through poorly sealed walls, roofs, windows, doors and other penetrations. Until we get a house well sealed and partner it with an adquately designed energy recovery ventilations system I think money is wasted on additional insulation.As you say in your foreword Understanding insulation and using it effectively are key to achieving passive comfort and energy independence. Using it effectively means spending the time necessary to tighten up a home, to take advantage of site condtions, southerly exposure, overhangs and thermal mass and to make intelligent choices on heating and cooling equipment and capacities. The title of the book uses today’s sexy energy words green and insulation which will help sell the book, and that is good. I suspect Alex Wilson emphasizes the importance of insulating effectively, and as builders of energy efficient homes we need to emphasize that energy sexiness isn’t quantified by simply in inches. 36-24-36 is not the all encompassing measurement of sexiness any more than my 12 inches of blown cellulose is the ultimate measurement of energy efficiency.

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