Title How do you build an energy efficient house from scratch?
October 22, 2005
Burlington Free Press
Written by: Eve Thorsen Correspondent
How do you build an energy efficient house from scratch? That's the question Chris Granda and his wife, Bonitta Steuer, asked themselves when they decided to build their home in Richmond.
Granda is a senior project manager at Vermont Energy Investment Corporation, a nonprofit organization that promotes efficient energy use. So when he and his wife explored building a family home for themselves and their two children Maddy, 9, and Nicholas, 5, he knew the approach he should to take.
"I knew I had to practice what I had been preaching, and I had always wanted an energy-efficient house, but at the same time I knew how much we had to spend, so we were on a budget," Granda said.
Working with designer Stefan Richter, builder Jim Huntington and consultant Peter Schneider, the couple developed a construction plan that maximized energy efficiency. The couple is in the final stages of constructing a 2,700-square-foot custom-built house that will cost them about $47 a month for heating, lighting, hot water and general energy use. Here's how they kept the lid on energy costs.
Size
Richter said one of the key energy-saving decisions made at this initial stage was to build a modest 2,700-square-foot house.
"It's going to be much easier to heat, and maintain and cool, and it's even easier to clean," Richter said. "It's quicker to build and it's more cost-effective as well. Bigger isn't always better."
Huntington agreed. He's been building energy-efficient homes for 25 years and his key piece of advice is: "Make it smaller. Less quantity and more quality."
For a custom-built house, 2,700 square feet is small but, said Granda, it fit in with the family's approach.
"We wanted to not spend any more money on space than we needed to," he said. "We wanted to spend the money on detail and energy efficiency."
Site
"Site was the most challenging thing, because they were interested in getting a lot of passive solar gain and daylight, but at the same time all the dramatic views on the site were focused on the north. This made a tough balance, because generally you try to avoid glazing north walls," Richter said.
The compromise was in orienting the house so that solar panels could get maximum daylight on the south, while on the north side they included many windows so they could enjoy the views.
"This house has more energy-efficient windows than you would normally have in an energy-efficient home, but that's one of the trade-offs," said Granda.
Insulation
This is another huge piece of energy-saving design. The Granda home features spray-applied urethane foam in the walls, a vaulted ceiling, and a 2-foot-depth of recycled wood cellulose insulation sprayed on the flat ceilings. Together, they provide a high insulation value per inch while significantly reducing air infiltration.
"We've probably done the best insulation system you can have," Huntington said. "It has closed cell foam. Many houses are insulated with fiberglass, which doesn't have anywhere near the insulating value or make the house as tight as this foam."
Fiberglass insulation has an R17 rating, whereas four inches of foam has an R28 rating. The higher the R-value, the more effective the insulation
Granda helped improve the insulation by squeezing a bead of caulk all the way around the inside perimeter of the house where the concrete foundation joined the wood construction. He chose spray-foam insulation because the foam can be sprayed into the smallest cracks, giving a tighter seal. He also asked that insulation be placed under the concrete slab instead of using radiant heat, so that the basement would remain at the same air temperature as the rest of the house.
Another insulation trick that Granda used in the building was to have the walls constructed 24 inches on center rather than the usual 16 inches. This not only used 25 percent less wood -- a longer-term energy conservation -- but also cut back the possibility of cold air infiltration.
"Fewer joists reduces the number of thermal breaks, joints that create cracks where cold air can infiltrate. More thermal breaks means the total insulation value of the wall will be degraded," Granda said. "Builders don't like to do this, they don't want to accept it."
Windows
All the windows are Energy Star-rated windows, which lower heat loss, decrease air leakage, and create warmer window surfaces that improve comfort and minimize condensation. The couple chose double-pane windows with Low-emittance (Low-E) coatings and argon gas between the panes. Granda said they could have chosen windows with an even lower rating, but the couple decided that the cost of importing them from Canada adversely tipped the cost-energy saving equation. They had help choosing their windows with a computer model available through Efficiency Vermont. This presents the various energy savings that could accrue by using various sizes and types of windows.
Wastewater heat exchange
The basement plumbing includes a Gravity Film eXchanger (GFX), a simple
plumbing device that replaces a section of vertical drainpipe with an
all-copper heat exchanger.
"It's pulling the heat out of the hot water before it can leave the house and go into the septic field," Granda said. "Hopefully, along with the solar panels on the roof, all of that will buy us enough hot water for my daughter to take her 20-minute showers."
The heat exchangers consist of 2-inch and 3-inch diameter lengths of copper drainpipe with half-inch tubing coiled tightly around them. As hot water is used, it goes down the drain and the heat is transferred to the exchanger.
Up to 85 percent of the heat from the wastewater can be transferred to the cold supply water through the copper and significantly preheats the incoming water, therefore reducing the work of the water heaters.
Heating
Granda and Steuer chose a modulating and condensing gas boiler with greater than 90 percent efficiency for space heating. They coupled that with an indirect water heater which operates as a zone off the boiler. This is the most cost-effective and efficient water heating option when used with a high-efficiency boiler.
"Our choice of fuel was propane because we're using propane for cooking and the dryer. If you can just have one fuel and buy more, you get a better deal," Granda said. "Propane is greener than oil, and gas boilers are generally more energy efficient than oil."
The couple chose not to use radiant heat in the house or the concrete foundation.
"Radiant is the big rage, but often it's not the most efficient solution, especially in a house that's spending a lot on insulation," Richter said. "It's much more of a comfort heat source, it's not about efficiency. But a lot of people put it in their basement slab so the whole basement stays at a specific temperature."
Granda chose instead to focus on insulation of the foundation, thereby keeping it in the thermal envelope of the property.
Ventilation
The house features a heat recovery ventilator (HRV) system, which provides a gentle circulation of fresh air throughout the home while lowering indoor air pollutants, odors and window condensation. The HRV will exhaust the stale, moisture-laden air while simultaneously brining in the same amount of fresh makeup air. The two airstreams pass each other in a heat exchange core, allowing much of the heat from the stale air to be transferred to the fresh incoming air without any mixing of the airstreams.
"The idea is that the house is so tight that you need something to keep the air clean and fresh," Granda said. "Tight homes also get too humid in the wintertime, creating condensation on the windows, and this prevents that."
Solar water heating system
On the south side of the house, Granda has positioned solar panels on the sun room roof. The solar panel system features a pumped flat-plate collector solar water heater in which a nontoxic antifreeze solution is pumped through a collector, an insulated box glazed with high-solar transmission glass with a black absorber surface, and that fluid in turn heats potable water in a storage tank via another pump and heat exchanger.
Appliances and lighting
All the appliances are Energy Star rated including the refridgerator, dishwasher and clothes washer. The owners had help in choosing these at the Energy Star Web site, www.energystar.gov, which features different products and explanations on how each differs from the standard.
The couple also designed every room with halogen lighting in mind.
"There's not going to be a single conventional light bulb in this house," Granda said. "We have three or four different kinds of halogen lights in the dining room for dimming and color. When you're looking at efficiencies paying for themselves quickly, one that really works that way is lighting. We save two-thirds to three-quarters of the cost of regular lighting."