Energy Efficiency and the Passive House

The past year has been one of weather extremes. The winter of 2009-2010 in Virginia saw more snow than had fallen in over a quarter of a century. The summer saw almost seven weeks of days near 100 degrees. Nonetheless, Virginia has a moderate climate and I benefit in the winter by having my roof absorb heat and the southern open orientation of my house. Throughout the summer the same southern orientation results in extra load on the air conditioning/heat exchanger, but provides the optimal conditions for my solar photovoltaic panels. (My husband enjoys the cooler months when he is allowed to open the southern drapes to experience the full beauty of our setting.) My most successful sustainable living project to date has been the insulation of my attic which effectively thermally isolated the attic from the rest of the house. According to the US Department of Energy heating and cooling account for about 56% of the energy use in a typical U.S. home, making it the largest energy expense for most homes.

To further improve the energy efficiency of my home I have been saving up to install a ground source heat exchanger (commonly called a geothermal heat exchanger) when my existing system reaches the end of its life or just before the 30% federal tax credit expires whichever comes first. This past spring, the O’Neill home in Sonoma, CA became California’s first certified Passive House, and the first certified to the new retrofit standards. A Passivhaus or Passive House in English is simply a very well-insulated, virtually air-tight building that is primarily heated by passive solar gain and by internal gains from people, electrical equipment, etc. Energy losses are minimized. Any remaining heat demand is provided by a small heat exchanger. Though the standard was developed in cooler climates and at this time tends to work best at passive heating avoidance of heat gain through shading and window orientation is also part of the standard and helps to limit the cooling load. An energy recovery ventilator provides a constant, balanced fresh air supply. Overall, a Passivhaus is reported to have an R-value of 60.

Though the concept was first pursued in New England in the 1970’s, the first Passivhaus were built in Darmstadt, Germany in 1990 and the standards were developed out of those projects. The Passivhaus standard includes an airtight building shell measured by blower-door test; an annual heat requirement ≤ 1.39 kWh/sqft/year; and primary energy ≤ 11.16 kWh/sqft/year. In addition, there are some recommendations that vary with climate. Worldwide the estimated number of passive houses ranges from 15,000 to 25,000. Passive houses incorporate high performance triple-glazed windows with solar films and argon gas, super-insulation, an airtight building shell, limitation of thermal bridging and balanced energy recovery ventilation make possible extraordinary reductions in energy use and carbon emission. The result is home that reportedly saves up to 90% of space heating costs, and reportedly provides excellent indoor air quality. If every building in America was a Passivhaus we could reduce our energy use by almost half.

The O’Neill home in Sonoma cost $500/sqft to retrofit, my house cost less than one fifth of that to purchase and came with acres of land. It is fair to say that I will never spend $500/ft sq to retrofit my home as a certified Passivhaus nor for that matter a LEEDs certified home. (About 39-percent of the points for LEED certification are energy related.) However, I think that despite the currently fashionable push into renewable energy, the real progress in reduction of energy use will be in insulation, strategies to reduce thermal bridging, and passive house techniques. Modifying our transportation behavior and reducing the energy used in our homes and buildings could change our national energy use significantly and it is within our control. Now that I have taken care of the attic insulation retrofit, I suspect that thermal bridging on the exterior walls combined with air leakage are the primary locations of heat loss and gain for my home and many others. To maximize the effectiveness of any future planned energy use improvement projects, I plan to investigate and incorporate (if possible) some of the design principals gleaned from the new Passive House retrofit standard and US Department of Energy recommendations in my next energy project.

CALGreen and LEEDS

I do not know if CALGreen is adding fuel to the fire that is currently the AB 32 debate in California, but back in January 2010 the California Building Standard Commission passed an amendment to the building code to create a state wide green building code in California to go into effect in January 2011. This green building code is known as CALGreen. The CALGREEN Code applies to all residential, commercial, hospital and school buildings, ensuring that every new building in California is built using environmentally advanced construction practices. While a mandatory code will allow California’s builders to build to a certifiable green standard without having to pay fees for third-party programs, compliance with the new standards will add to the cost of construction and difficulty in getting new housing permitted. This will increase both the volatility and ultimately cost of housing in California.

Various municipalities, such as San Francisco and Berkeley have mandated that new construction be LEED certified or in other ways “green” this is the first state wide standard for green building. If you recall, under AB32, California must reduce greenhouse gas emissions by 25 percent by 2020, returning them to 1990 levels. The mandatory CALGREEN code provisions will be inspected and verified by local and state building departments, who will have to be trained in the new standards (no doubt under stimulus funds for green jobs). This initiative is designed to reduce greenhouse gas emissions and conserve water, by incorporating a set of environmental standards into the existing building code. Buildings in California account for one-quarter of the state’s greenhouse gas emissions. The California Air Resources Board estimates that CALGREEN will avoid 3 million metric tons of CO2 equivalents in 2020 which is 5.6% of the reduction necessary to meet the goal. It will also reduce water use by 20% and divert 50% of construction waste to landfills. CALGreen requires:

20% mandatory reduction in indoor water use, with voluntary goal standards for 30%, 35% and 40% reductions;
Separate water meters for nonresidential buildings’ indoor and outdoor water use, with a requirement for moisture-sensing irrigation systems for larger landscape projects;
Diversion of 50% of construction waste from landfills, increasing voluntarily to 65% and75% for new homes and 80% for commercial projects;
Mandatory inspections of energy systems (i.e. heat furnace, air conditioner, mechanical equipment) for nonresidential buildings over 10,000 square feet to ensure that all are working at their maximum capacity according to their design efficiencies;
Low-pollutant emitting interior finish materials such as paints, carpet, vinyl flooring and particle board.

The U.S. Green Building Council (USGBC) currently offers a set of voluntary green building standards known as Leadership in Energy and Environmental Design (LEED) by far the most popular and well-known green building certification program in the nation. LEED operates as a point-based certification system, where building developers can reach the Certified, Silver, Gold and Platinum levels of ‘greenness’ in different ways hopefully appropriate to the local conditions. While the LEEDS point-based system allows flexibility for building developers, it has been criticized for allowing too much freedom in choice. Also, LEED certification requires an investment of money to pay for third party verification and periodic verifications. The CALGreen standards will be part of the building inspection process, the cost to train and implement born by the taxpayer instead of the builder and buyer. California could well end up like Europe, with laws to prevent new construction and expansion of existing home footprints.

LEED and Your Home

The U.S. Green Building Council (USGBC) are the people who created and maintain the LEED standards, the familiar Certified (used to be Green), Silver, Gold or Platinum rated buildings. LEED is the leading green building certification system, intended to verify that a building or community was designed and built using accepted generalized strategies aimed at: energy savings, water efficiency, CO2 emissions reduction, improved indoor environmental quality, and stewardship of resources. The standards tend to be fairly generalized and not region specific, but should be appropriately applied to produce an environmentally responsible building. LEED provides building owners, operators and buyers a concise and measurable framework for identifying, implementing and comparing green building design, construction, operations and maintenance. The USGBC has expanded these basic standards from commercial construction to operations to single family homes and now have created REGREEN Residential Remodeling Guidelines. Not all of us can rush out and buy a LEEDS certified home. There is a tremendous amount of existing housing in the United States and the REGREEN guidelines can offer a roadmap to improving the environmental performance of our existing homes. Green remodeling also reduces the environmental impacts of remodeling, including energy, water, and materials consumption; waste generation; and harmful emissions, both indoors and out. If you want to take a look at some of the things you could do to improve the environmental performance of your home, explore the ideas and recommendations on the USGBC site. An example is “Reflective (high-albedo) roofing materials can help improve the thermal enevelop of your home.

There are eight areas of consideration in a LEEDS home. How these aspects are actually measured and quantified is the basis of the LEED scoring system. The first area is indoor air quality, a LEED home is designed to maximize fresh air indoors and minimize exposure to toxins and pollutants. This involves addresses air circulation, mixing and off gassing from building materials and furnishings. The second area is energy efficiency. In general LEED homes are built to use 20-30% less energy than the standard size typical home. Larger homes and homes that do not meet the goals in other areas can up their score by reducing the energy footprint of the home with energy generation. Most of the glamorous LEEDS homes you see need to meet a very strict home energy rating index because their footprint exceeds the reference size. An expensive, but quick way to neutralize size in LEEDS score is to shoot for a net zero home.

The next area is water efficiency; here is one of many areas where the standards lean towards urban and suburban issues. According to the USBGC wasteful water use is both costly and risky and tied to wasteful energy use: According to the U.S. Department of Energy, as much as ¼ - ½ of the electricity used by most U.S. cities is consumed at municipal water and wastewater treatment facilities. The LEED home standards encourage limiting water use and encouraging water reuse with grey water systems. In reality, water availability is a local issue. My water is supplied by a private well drilled into an incredibly productive aquifer. My wastewater is treated on site by an alternative on-site septic system. Thus my water is directly recycled back into the watershed. Water shed protection is the issue I worry about not water efficiency, though two decades in California has left me incapable of wasting water and our household water use is actually very low. Site Selection is another area where the standards judge based on old preconceptions. LEED encourages homes that are close to schools, shopping, work and transit. However, my husband and I live, work, and relax from home. Access to high speed internet, cable, and food supply sources were the important location issues we considered. In truth, I leave the house on average, three times a week. Coming from California, I worried about water availability, water quality and protection of the water shed.

The other areas of the LEED scoring system are site development, materials selection, resident awareness and innovation. It is essential that building a home and living in it not cause erosion, interfere with natural habitats and pollute waterways through storm water runoff and other actions. How you live in your house is just as important as how the house was built. At the end of the process, a home is awarded points in each area. Based on the number of points it receives, the home can be certified at one of the four levels: Certified, Silver, Gold or Platinum. LEED certification is both cool and desirable; however, it is not enough to ensure an environmentally responsible and sustainable existence. That is the result of all the elements of your life. The LEEDS tools especially the REGREEN guidelines are great tools for knowing what choices we have for our homes, but the sustainability and environmental impact of our lives is based on the total of all our choices.