Greening Martha : Wrapping it tightly may be the energy saving solution for your house
By Steve Myrick
Published: March 11, 2010
Conservation, while it isn't as flashy as a windmill on the hill or solar panels on the roof, is often the most effective way to reduce energy costs, according to Island contractors who specialize in energy-efficient buildings. One conservation technique, known as a deep energy retrofit, takes conservation to extremes, and it can yield extreme savings. In such a retrofit, contractors try to achieve at least a 50-percent reduction in energy use. Some homes can reduce energy use by 90 percent.
The exterior of the home is wrapped in a tight, continuous air barrier, and super-insulated as part of a deep energy retrofit. Click on photo to enlarge. Photos by Steve Myrick Deep energy retrofitting is an integrated approach to tightening up a home. It's not a new idea. Intrepid American pioneers kept prairie winds and dust storms at bay by chinking the gaps in their cabin walls. Technology, naturally enough, has progressed way past stuffing rags between logs.
The fundamental conservation idea is to seal the building as tightly as possible with layers of insulation and other thermal barriers. It requires a variety of techniques, using a variety of materials. The goal is to create a tight wrapping around the house, from foundation to roof, with no gaps where energy can escape.
Deep energy
The future is now in Aquinnah, where a newly purchased home with spectacular views of Vineyard Sound is undergoing an extensive deep energy retrofit. The costs are significant, $170,000, or about 20 percent of the entire renovation project.
Inside, sealing and insulation are expected to lower energy use by as much as 90 percent. Click on photo to enlarge."It's a wonderful site, it's a terrible house," said John Abrams, president of South Mountain Company, which is doing the retrofit. The 2,400-square-foot home was completely gutted, and all exterior siding and roofing removed.
The contractor installed a tight thermal and air barrier, with all seams sealed. Various kinds of insulation were used, including open cell foam, closed cell foam, rigid fiberglass insulation, rigid foam exterior insulation, and cellulose. Each has its own characteristics, and each was chosen to fit the particular application.
For example, rigid fiberglass was used on the foundation, because bugs and critters don't like it. Closed cell foam was used to insulate the roof, because it makes a very tight seal in places where it is otherwise difficult to close small gaps. The roof was also built out, to allow for thicker insulation to be installed.
Rob Meyers, the energy analyst for the project, estimates the insulation value of the finished walls will be R-40, and the finished roof, R-31. The insulation value of conventional fiberglass insulation ranges from R-13 to R-19.
The house is so tight that it needs forced ventilation to bring in fresh air. Even the ventilation adds to the energy efficiency. As cold, fresh air is pumped in, it passes over the warm, stale air, and about 60 percent of the heat is transferred. It's like pre-heating fresh air.
Five air-source heat pumps will provide heating and cooling, powered by electricity generated by solar panels on the roof.
Cost calculations
While the Aquinnah house is a big budget production, many of the techniques used in deep energy retrofitting may be achieved at lower cost.
"What we might do is strategize over a couple of years," said Bill Potter, president of Squash Meadow Construction in Vineyard Haven. "Do a little bit here, a little bit there. There are a few projects where we've had that strategy, shooting for a 30- to 50-percent improvement in energy efficiency, rather than 50 to 75 percent."
Mr. Potter says the first place to start is usually with an energy audit, which are done for free by Cape Light Compact. This is also often the first place to start saving. Cape Light Compact has funds to subsidize a variety of home energy improvements.
"I think education and awareness is critical right now," Mr. Potter said this week. "Right now, in today's market, there's fear. What people need to do is walk through that fear and become aware that it's not going to cost them an arm and a leg. The bottom line is, it all makes sense."
Any house can be retrofitted. If you need a new roof, that could be the most economical time to make some energy-saving changes. Still, it is difficult to figure whether a deep energy retrofit makes economic sense, because retrofit is designed to last many decades, and no one can predict the cost of energy over that time.
"The payback is very long," Mr. Abrams said. "But you don't get an opportunity to do it again in your lifetime. At the end of its life, 2050, 2060, what's energy going to cost? Are we going to have any?"
