Deep Energy Cuts for a Fresh Start
Asdal Builders achieved an 80% reduction in energy use in an existing home without sacrificing the comfort of the occupants.
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We know deep energy reduction is possible with new construction, but is there any hope for existing homes? Bill Asdal of Asdal Builders, LLC, set out to find out with a 1,300 ft2 1930s era bungalow in Pittsburgh, Pennsylvania. Bill and his team of staff and subcontractors did a total rehab, keeping the shell but stripping the walls down to the studs to seal, caulk, and insulate, the building envelope, while upgrading mechanicals, appliances, and lighting. The home went from an original HERS index score of 185 to an amazing 65, a score that puts the home well above state code requirements and within the 70 points required to meet DOE’s Building America Builders Challenge (see “Building America’s Builders Challenge”).
Asdal has been building and remodeling homes for more than 30 years but says this is his most energy-efficient home yet (see “Builder Profile). We think we’ve been doing it right for 32 years. But every day you learn something new. We just keep trying to get better and better at it. Once you get energy efficiency in your blood, you can’t build any other way,” says Asdal.
Asdal took on the rehab as a demonstration project for ACI, a nonprofit organization that conducts national and regional home performance conferences. Asdal sees the demonstration project as an opportunity to build a bridge between the knowledge base at the conferences and the broader building community. It's a solid model that proves these concepts can work. We’ve got the numbers to prove it,” says Asdal. An analysis of the project included a blower door infiltration test and modeling of energy use. Because Asdal wanted to show that the energy efficiency gains he achieved are accessible to the ordinary builder, he didn’t incorporate a lot of high-tech gadgetry but instead relied on readily available materials, applied with care.
Asdal points out that it’s a win-win outcome all the way around. “Reduced consumption, without sacrificing comfort and lifestyle, is an immense societal goal. This is the ultimate recycling project—100% of the structure was saved; we didn’t add one square inch to the building footprint,” says Asdal. The homeowner gains a finished, insulated basement that adds 400 more square feet of livable space, plus updated appliances, guilt-free energy bills, an estimated energy use savings of a whopping 81%, and a healthier home that should last well into the 21st century.
Energy Efficiency and Innovations
The home had a full, uninsulated basement. The first step was to caulk the wall plates, air seal the unfinished walls, and apply an interior layer of rigid foam insulation. Over that, the inside walls were framed, and insulated with fiberglass batts for a total insulation value of R-20.
Above-grade 2 x 4, 16-inch-on-center (OC) walls were air sealed and insulated with 4 inches of blown cellulose. Exterior aluminum siding was replaced with a Crane Smartcore siding product with rigid polystyrene foam insulation, applied over Tyvek house wrap that was properly caulked and taped. Vaulted ceilings were filled with 10 inches of blown cellulose, and flat ceilings were insulated with 12 inches of blown cellulose. Band joist areas were air sealed with spray foam and pieces of rigid foam insulation. Doors and windows were replaced with high-performance products properly installed.
MaGrann Associates conducted blower door and other tests. The infiltration test showed the retrofitted home to be very tight,” MaGrann reported, “particularly considering its age. MaGrann Associates usually sets a target of 1 CFM50 per square foot of conditioned space. We rarely see less than 0.5 CFM50. This home
The house was heated with steam heat from a natural gas boiler that was fairly new, but Asdal chose to replace it for safety reasons. The existing boiler used atmospheric combustion, drawing oxygen from within the home, which can be a problem in a tightly sealed home. The new boiler is a sealed-combustion, power-vented unit, meaning that it draws combustion air from the outside via a dedicated pipe. This unit has a higher annual fuel utilization efficiency (AFUE) and also heats the domestic hot water. Potable hot water is also heated with an electric tankless water heater. An old central A/C unit and leaky ducts were removed from the house and not replaced. Asdal expects that central air A/C will not be needed, thanks to the increased insulation, air sealing, and mechanical ventilation provided by two energy recovery ventilators (ERV), timer-controlled bathroom fans, and ceiling fans. Energy Star appliances, lighting, and a programmable thermostat add to the energy efficiency package. Table 1 shows the energy efficiency upgrades that Asdal made; Table 2 shows how they changed the home’s energy score.
Asdal thinks the secret to getting such a low HERS index score was really focusing on doing things the right way. Air sealing correctly makes a house far more energy efficient. “We worked with a terrific local remodeler, plus a host of very reputable trade contractors. We work with the same contractors over and over. Every single one of them got retrained when they started working with us—the guys installing the pipes, the guys putting in the windows, the guys applying the caulk and foam, the guys putting on the siding—everybody. To get to these kinds of numbers, everybody has to know what they are doing; everybody has to be on their game. There’s a lot of learning that still needs to happen in the industry.”
The sealed-combustion boiler, mechanical ventilation, and air sealing details mentioned above have health as well as energy efficiency benefits. They keep out CO; they vent other house fumes, and they keep out pollen, humidity, and pests. Asdal also worked with manufacturers and suppliers to find healthy and sustainable products to bring into the home—such as cork flooring, and low-VOC paints and finishes.
Dollars and Sense
Is energy efficiency rehabbing commercially viable? Yes, it absolutely is,” says Asdal. Consumers benefit from a better home overall and lower operating costs. Asdal estimates that rehab costs on this home were about 15% higher than standard construction costs, due to the energy efficiency upgrades. “We went from a HERS index of 185 to 65 with a 70-year-old shell. Those are powerful results,” says Asdal. “There was nothing haphazard about this. The work is part of a long-term effort to improve energy efficiency in our existing housing stock.
“Energy bills are shaping the impetus,” Asdal says. “Make no mistake: This effort is nothing short of building a new industry around mainstreaming home performance. The road map I see is ‘remodeling’ the remodeling industry to ramp up our skills of analysis, pre- and post-testing work, and delivering on promised performance. It includes reshaping consumer thinking—from focusing on first cost to focusing on life cycle costs and operational costs. Reducing consumption without sacrificing comfort and lifestyle is an immense societal goal. This effort must succeed. We all must act now to push this energy consumption–lifestyle equation to actionable results—or the next generations will pay with a contracted lifestyle.”
“The fact is that 39% of domestic energy consumption is in buildings. This is more than all our transportation energy consumption combined. As we strengthen our homes for the next generation, our reduced dependence on fossil fuels can help keep America on the front edge of global leadership,” says Asdal.
The demonstration home described in this article is neither zero energy nor free of the grid. What it is, however, is a smart housing solution, well delivered to meet a market need for clean, affordable homes. Delivering on this premise,” says Asdal, “we all win.”
Theresa Gilbride is a scientist at the Technology Planning and Deployment Group at Pacific Northwest National Laboratory, Richland, Washington, which helps conduct the Building America program for the U.S. Department of Energy.
For more information:
For more on ACI, go to www.affordablecomfort.org.
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