Green Building Standards

A reality that many homeowners are familiar with is the cost of energy required to heat or cool one's home. Estimates from various European sources show that on average 70% of household energy use is directed towards maintaining a comfortable living temperature. [1] This is not an insignificant number; it is estimated that the on-site energy use of the residential sector in the US is 2.1 x 10¹⁹ joules/year, approximately 20% of the total energy use in the nation. [2]

As the public becomes more aware of the upcoming energy crisis, there is an increasing demand for goods and services that are more energy efficient. Although consumers often turn to simple steps, such as changing lightbulbs for fluorescents and choosing more energy efficient appliances, these will not have a large impact on the final energy budget. A substantial impact in both energy consumption and consumer costs requires a substantial initial outlay in both time and money to renovate or build a new home according to "green" standards.

Multiple building standards have sprung up around the world focusing on energy efficiency, which reduces long-term energy costs for the consumer as well as decreasing the energy demand placed on the infrastructure. Much of the movement in this area has been focused in Europe and the US. The most common example of this in the US is the LEED Certification provided by the US Green Building Council, although the National Green Building Program also provides a green building standard. [3,4]. Both of these standards focus on areas such as heating, cooling, lighting, and efficient use of available resources. In Europe, one standard that has received a substantial amount of attention is known as PassivHaus, which focuses primarily on heating and cooling, although incorporation of further energy and resource saving techniques is highly encouraged. [5]

The effectiveness of LEED certification at increasing the energy efficiency of buildings is claimed to be between 10% peak demand reduction and 30% overall efficiency. [6] However, questions have been raised regarding the methodology used to produces these comparisons, with more rigorous analysis of the data suggesting that the energy efficiency of the buildings has little correlation with their LEED certification and more guidance is needed. [7] There are also a number of criticisms regarding the increased cost of construction and the cost of certification which is non-trivial. As such, LEED certification remains limited largely to commercial scale projects and out of reach of the average homeowner, although there are increased efforts to build sustainable homes.

The PassivHaus standard introduced in Europe in 1989 instead focuses on the home. The definition of a passive house is "one in which a comfortable interior climate can be maintained without active heating or cooling systems." [8] Houses which meet the passive house standard have an annual heating requirement of 15 kWh/m² per year, while the entire primary living area energy consumption may not exceed 120 kWh/m² per year, including heat, hot water, and household electricity. [9] Comparison of houses built to the PassivHaus standard to alternate low energy home standards have found that the PassivHaus standard fares well due to the emphasis on conservation before the introduction of alternative energy techniques. [2]

The energy reduction of the PassivHaus standard is achieved in a number of ways. Good insulation on all external surfaces is required, with walls required to have a U-factor of 0.15 W/m²K or less while windows should have a U-factor of less than 0.80 W/m²K and a solar heat-gain coefficient of approximately 50%. Home design and placement is important in order to take advantage of such features as natural solar heating (southern exposure) and cooling (shade). It is extremely important to have a well sealed house, with minimal air leakage. [10] Fresh air from the exterior is then brought in through the ventilation system, passing through underground ducts which use the ground as a heat exchange to preheat (or precool) the air before passing it through an air to air heat exchanger which passes heat from (or to) the exhaust air to (or from) the incoming air. [11] Additional suggestions include the use of solar heating for hot water and energy efficient appliances.

Compared to the standard homes in Germany, the PassivHaus standard represents a 90% reduction in the energy requirements to heat and cool the house. [12] Focusing solely on the heating and cooling requirement and assuming no other changes in household energy use, it is possible to see what kind of impact these changes could have on the global energy budget.

For the purposes of this exercise, we will assume that the heating/cooling amounts to 50% of the household energy budget - a somewhat conservative estimate depending on the locale. If we start with the average German usage level of 150 kWh/m² per year, this results in a total household energy usage of 300 kWh/m² per year. Reducing the heating/cooling portion of the budget to 15 kWh/m² per year results in a final value of 165 kWh/m² per year (or if you prefer SI units, 594 MJ/m²) - a 45% reduction in the energy usage per m² per year. Applying this reduction to the broader figures above (assuming we had a magic switch that could convert all houses to the PassivHaus standard) would reduce the total energy use in the US by 9%. These numbers are by no means accurate and represent at best a back of the envelope calculation but do demonstrate the significant energy savings that could be realized in developed nations through greener construction standards.

The techniques highlighted here are relatively simple ones that could be used as a sole solution or in conjunction with more conventional heating or cooling methods in areas of the country where this is insufficient to maintain a comfortable living temperature. The exchange of internal and external air promotes higher air quality indoor by reducing indoor air pollution, which has become a more relevant concern in the past ten years. Additionally, none of these techniques require novel construction techniques but instead attention to and strict adherence to good construction. [10] While the need for quality workmanship may result in an increase in costs initially, as well as the increased need for good insulation, the end result will provide increased financial security against increasing energy prices. [2,11]

© 2010 Linda Thompson. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.

References

[1] R. Galvin, "Thermal Upgrades of Existing Homes in Germany: The Building Code, Subsidies, and Economic Efficiency," Energy and Buildings 42, 834 (2010).

[2] D. Parker, "Very Low Energy Homes in the United States: Perspectives on Performance from Measured Data," Energy and Buildings, 41, 512 (2009).

[3] "LEED," U.S. Green Business Council, 2010.

[4] International Code Council and National Association of Home Builders, National Green Building Standard (Builderbooks, 2009).

[5] T. Zeller, "Can We Build in a Brighter Shade of Green?" New York Times, 25 Sep 10.

[6] G. Kats et al., "The Costs and Financial Benefits of Green Buildings: A Report to California's Sustainable Building Task Force," October 2003.

[7] G. R Newsham, S. Mancini and B. J. Birt, "Do LEED-Certified Buildings Save Energy? Yes, but ...," Energy and Buildings 41, 897 (2009).

[8] W. Feist, "Passivhäuser in Mitteleuropa," Doctoral Dissertation, Darmstadt/Kassel, 1993; H. Krapmeier and E. Drössler, CEPHUS: Living Comfort Without Heating (Springer, 2001).

[9] S. Hastings, "Breaking the 'Heating Barrier': Learning from the First Houses Without Conventional Heating," Energy and Buildings 36, 373 (2004).

[10] J. Schnieders and A. Hermelink, "CEPHEUS Results: Measurements and Occupants' Satisfaction Provide evidence for Passive Houses Being an Option for Sustainable Building," Energy Policy 34, 151 (2006).

[11] U. Janson, "Passive Houses in Sweden," Licentiate Thesis, Energy and Building Design, Lund University, Report EBD-T-08/9 (2008).

[12] V. Badescu and B. Sicre, "Renewable Energy for Passive House Heating: Part I. Building Description," Energy and Buildings 35, 1077 (2003).