We go back, back, way back - to look at a home built in the Colonial style in 1928, as it undergoes a thoroughly modern retrofit.
“It was an energy efficiency disaster,” says the homeowner. “Johnson was so accurate he did not put dampers in the five fireplaces because in a colonial home you never let the fires go out. And there was absolutely no insulation in the walls or in the attic.”
For four years, EarthCraft Virginia has been bringing high energy efficiency, enhanced indoor air quality (IAQ), and environmentally responsible design to single- and multifamily new construction in the state of Virginia. It is an adaptation of the EarthCraft Green Builder program developed 12 years ago in Atlanta, Georgia, by Southface Energy Institute and the Greater Atlanta Home Builders Association. An EarthCraft technical advisor is assigned to each project to advise subcontractors and perform quality assurance inspections during construction to verify compliance.
With this historic and energy-inefficient home, EarthCraft recently completed its first single-family pilot renovation. In so doing, EarthCraft faced two challenges. The first was to create the first EarthCraft Virginia certification program for single-family home renovations. The second was to do so without compromising the historic value and character of the home.
History of a Renovation
It was 1978 when the current homeowner bought the 3,600 ft2 two-story home at an estate sale. Situated in Albemarle County, Virginia, the house stands on 65 acres and is surrounded by 200-year-old oak trees. As an architect himself, the homeowner says, “It was architecturally beautiful. I fell in love with it because I knew there was no one alive who could do that kind of detail work today.”
The house had an old coal boiler—complete with a coal storage room—that had been modified into an oil-burning furnace, along with a steam radiator system. All the windows were the original single-pane windows. All five colonial fireplaces were constructed without dampers. There were seven attics and a crawlspace, all of which were vented to the outside.
“I drilled holes and blew cellulose insulation into the cavity behind the walls and in the floor of the attic,” says the homeowner. “Then I found some rooftop dampers that I put on the fireplaces. In two fireplaces in the children’s room, I closed off the fireplaces completely and blocked them off. We converted the steam radiators to a circulating hot water system and put in a new oil-burning furnace system to provide heat for the old part of the house. For cooling in part of the house, we put in window air conditioners. I put an electric heat pump in the attic space above the two bedrooms in the center section, and another one that heated and cooled the center section of the house and master bedroom wing.” A renovation and addition to the kitchen space included storm windows, storm doors, and an air-to-air electric heat pump for that wing.
The next set of upgrades came in the early 1990s.The homeowner was a member of the American Institute of Architects (AIA) and the Committee on the Environment (COTE), which preceded the U.S. Green Building Council. As such, he regularly met with a group of architects from across the country. “We were trying to figure out how we could move the profession to thinking more about sustainable housing and energy efficiency. And I was trying to do as much as I could with my own house,” he says. Storm doors were added to the back of the house, and all the glass on the kitchen and family room wing was replaced with Heat Mirror glass—a product originally developed for skyscrapers. Heat Mirror—a trademark of Southwall Technologies—is a low-e coated-film product suspended inside an insulating glass unit. It has superior insulating and shading performance, allowing light, but not radiant heat, to penetrate.
“When the sun goes down in the west over the mountains, the whole back of my house gets the sun in the afternoon, and the kitchen would bake from 3 to 4 pm,” says the homeowner, who used his contacts at Rocky Mountain Institute, in Colorado, to track down the Heat Mirror product, which at the time was not available in the residential market. “I got the name of the fabricator in Ohio. I had a local window manufacture measure it and install it.”
In 2001 came the addition of a geothermal heat pump system to heat and cool the downstairs section of the house. The same loop with a different compressor was put in to run a second geothermal system for the upstairs in the center of the house. Always experimenting with new, energy-efficient, and clean technologies, the homeowner added a propane-electric dual-fuel system during a second renovation of the kitchen wing, as well as a propane water heater. “Propane is one of the cleanest of the fossil fuels, and when they advertised that the products were 96% efficient, I decided to try it,” he says.
The homeowner, who now runs an affordable housing foundation, was working closely with the EarthCraft Virginia program at its inception. “One day I woke up feeling frustrated that EarthCraft was providing me with reports about these wonderful houses in Virginia and I did not have one,” he says. “I wanted to be able to look in the mirror and know I was living what I believed in.” So he talked with EarthCraft and convinced it to use his house as a pilot project to launch the Single-Family Renovation certification program. He was willing to try any technology that might improve the energy efficiency of the home while working toward EarthCraft certification. EarthCraft started work on the house in November 2006.
|Future Plans for Continued Energy Savings
In an ongoing effort to become more energy efficient and environmentally responsible, and to get as close to a zero energy house as possible, the owner of this house is currently working on installing PV cells that he hopes will provide electricity for all his energy needs.
“I am in the process of building an equipment shed in the field south of the property,” the homeowner explains. “It looks like a shed from the front, and I will use it to keep my farm equipment. But on the back side it will have a 38° pitched roof with photovoltaic cells.”
PV cells convert sunlight into electricity. Sunlight is made of photons—small particles of energy that are absorbed by and pass through the material of a solar PV panel. The photons agitate the electrons in the material that forms the PV cell. As the electrons move, they are routed into a current, producing DC electricity. Wire conducts the electrons to an inverter box that converts the electricity from DC to AC. The AC current is compatible with the electrical system of the house.
“I will hook them [the PV cells] into the meter during the day and run the meter backward,” says the homeowner, explaining that Virginia is a net metering state. This means that if you generate more electricity than you use, your meter runs backward; the electricity goes to the utility; and you get a credit. “I hope to get to a net zero energy house,” the homeowner says, “—to produce as much from the sun as we are using.”
“He was really interested in making his house as energy efficient as possible,” says Charles B. Bowles, program technical director for EarthCraft Virginia, who headed up the project. Like the New Single-Family Home certification program, the Single-Family Renovation certification program provides a menu of items from which the homeowner can choose to get the minimum of 100 points required to earn EarthCraft certification. Points are awarded in various categories, including improvements to existing windows, doors, walls, foundations, floors, roofs, and attics; improvement or replacement of HVAC systems; improvements to ventilation and water usage; landscape and site waste management; and homeowner education. The house must also be inspected before, during, and after the renovation by a certified EarthCraft inspector. Along with the completed scoring worksheet, energy performance modeling must show a minimum of 30% improvement over prerenovation modeling.
“Prior to renovation, the house underwent testing to establish a baseline, including blower door testing, forced-air distribution systems testing, and pressure diagnostic testing,” says Bowles. “All this was gathered for the energy model to use for comparison after the work was completed, to make sure we improved energy performance by at least 30%.”
At the prerenovation investigation, Bowles’s blower door and duct leakage test on the house showed significant energy loss. “The home has seven attics, and there were numerous penetrations between conditioned and unconditioned space, which had been added over the lifetime of the house when installing updated light fixtures, attic fans, and electrical wiring. With the numerous penetrations, almost no effort had been made to air seal these leakage sources,” Bowles says. “Many of the interstitial cavities in the house were also used as ductwork. The crawlspace under the house was vented, which is not particularly good in this climate. All the forced-air distribution systems were leaking over 50% of system air flow capacity.”
The historic status of this house proved to be a challenge and limited how invasive EarthCraft could be to improve the house’s energy efficiency. “We were limited in what we could do because we did not want to compromise the historic significance of the house,” says Bowles. “The walls were double-wythe brick with plaster on wood lath strips in the main core of the house. In order to make changes, we would have had to take them down entirely. And most of the existing windows were original to the house, and the homeowner did not want to change them. We were looking for a 30% improvement over baseline, and the improvements that we discussed and agreed upon with the homeowner gave us what we needed for that level of improvement without destroying the historic authenticity of the design.”
The improvements that they chose focused on tightening the building envelope (without making window or wall modifications); upgrading the HVAC systems; putting the ductwork into conditioned space; and finding and installing an alternative, energy-efficient water-heating system.
To tighten the building envelope, the vented attics were sealed. “We went in with an industrial vacuum and removed all the old gray fiber insulation that was matted down on the attic floor,” says Steven A. Tetreault, president and owner of ThermalTec, in Williamsburg, Virginia, whose company did the work. “Then we went in with a 2-lb closed-cell sprayed polyurethane foam (SPF) and insulated the roofline of the attic rafters. The foam expands as you spray it, so it fills all the spaces and gives you a nominal 6.8 R-value per inch.”
The foam was sprayed to a depth of 4 to 5 inches, which gave it an R-value of 30 to 35. “The reason we sprayed the foam up the roofline and not on the floor was to encapsulate the whole attic, so they could bring the ductwork into conditioned space,” Tetreault explains.
Some of the work required cutting into attic spaces that were not accessible. The ThermalTec team entered through the existing gable end vents from the outside, sprayed in the foam, and rebuilt and sealed off the new vents on the way out to bring the attic into a buffered zone. Exhaust fans from the bathrooms were vented directly to the outside, rather than into the attic space, as they had been previously.
Old insulation, as well as debris, had to be removed from the numerous vented crawlspaces under the house. Then, to increase moisture mitigation and create a dry conditioned space to house duct and mechanical components, the crawlspaces were insulated as well. “We laid down a 20-mil reinforced poly liner for the ground cover and tacked it to the walls to encapsulate the entire space for conditioned space. Then we went in with the same foam we used in the attic and sprayed all the foundation walls,” says Tetreault. The 250 ft2 workshop-basement area was also sealed and converted to an unvented conditioned space.
To upgrade the HVAC system, the propane-electric dual-fuel system was replaced with a third geothermal system, making the house entirely heated and cooled by three geothermal systems. “We buried the circulation loops in the pasture to the south of the house,” says the homeowner, referring to the 150 feet of line per ton required to circulate the water-antifreeze mixture in the system. “And it has to be 18 inches down in this climate to be below the frost line. So we used a backhoe and went down 6 feet and put in six loops [to handle all three zones] that were 150 feet long each, and then stacked loops on top of each other and filled it in.”
Local HVAC contractor and energy conservation specialist Air Flow Systems, Incorporated, of Charlottesville, removed the insulation on the ductwork as well as the old duct tape. The duct tape was replaced with a mastic seal on all the joints, and the insulation covering was replaced. Energy Star-rated bath fans were installed to replace the old fans in the bathrooms and were ducted directly to the outside of the house.
Altenergy, Incorporated, of Charlottesville, replaced the propane hot water system with a solar-thermal system. Solar thermal is a cost-effective renewable energy water-heating system that collects the sun’s energy in the form of thermal or heat energy and uses it to heat water while significantly reducing your utility bill.
“We placed the solar array on an auxiliary wing that has a south-facing roof,” says Paul Risberg, president of Altenergy, speaking of the placement of the 52 evacuated tubes. On existing houses, arrays are usually placed on the best location possible to get maximum sun. “It was challenging, because it was a larger array than we do on most houses. We did that because there were a lot of trees around the house that we did not want to remove, so we had to compensate for the shade.”
Each copper tube is contained in two layers of glass separated by a 1/8-inch space that creates a vacuum. Each tube plugs into the system through a manifold located at the top of the array. “We circulate antifreeze through the system and it picks up heat from each tube. Then there is a storage tank in the basement that has a heat exchanger that takes that heat captured by the tubes and supplies his domestic hot water,” says Risberg. “A controller determines if there is potential solar heat—and if so, it turns on the pump and circulates antifreeze from the array into the storage tank. When it is dark or cloudy, the pump turns off—it only operates when there is heat being generated by the array.”
The lightweight tubes add about 5 lb per square foot to the roof load. One minor concern with placing them on the roof was wind resistance, so the mounting procedure was critical. “He has a metal roof on that section of the house, so we used a nonpenetrating mounting system,” says Risberg. “His array is mounted on the seams of the metal roof with no penetration. His is unusual in that all the line sets are concealed within copper drainpipes to match the rest of the original copper drainpipes that were already on the house.”
The de-super heater on the geothermal system is also integrated into the solar hot water system. During the cooling season, the waste heat of the geothermal system makes hot water that is plumbed into the domestic hot water system. Old tanks that were already installed on the property were recycled to give ample storage—about 240 gallons—for hot water. Risberg explains that there are a total of three storage tanks—one tank is solar, one tank is designed to accept rejected hot water from the geothermal system, and the third is a backup tank that is a traditional electric hot water tank. “So if the backup hot water tank is not receiving enough hot water from the solar or the geothermal system, then it produces hot water. That way when he turns on the tap, he always has hot water,” says Risberg.
“It has worked beautifully and contributed a significant amount to our energy savings,” says the homeowner. (For what the future holds for this historic home, see “Future Plans for Continued Energy Savings,” p. 42.)
The project was completed and the house was EarthCraft certified in August of 2007. The homeowner has been tracking energy usage since then, with remarkable results (see Table 1). “Absolutely right away we saw savings on our energy bills, as well as the comfort in the home,” says the homeowner. “We saw about 42% savings just in that first year.”
Deborah Rider Allen grew up in Richmond, Virginia, and has been writing in the building industry for more than 20 years. She writes for business Web sites and publications, including Home Energy, the Richmond Times-Dispatch, and Housetrends Magazine.
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