L'excellente étanchéité des maisons permet de réduire les factures d'énergie-news-325

Last month, I joined about 40 other volunteers, armed to the teeth with materials to weatherize a two-family home. Despite the rain and a few errant squirts of insulating foam, we made the leaky New England home significantly more energy efficient, largely by sealing all manner of leaks.

We won’t know the financial impact of our work until after the winter months, but it will undoubtedly lower the residents’ heating and electricity bills in future years. Along the way, we learned a few things we could do at our own homes, met some people in the community, and felt good about volunteering our time.

A blower door measures how air tight a home is by measuring air flow at a given air pressure.

Credit for the idea behind our barn raising goes to Cambridge, Mass.-based HEET, or Home Energy Efficiency Team, a volunteer group that has organized a number of these events over the past year. The goal isn’t just to weatherize one building; it’s to teach as well. After all, many people want to be a little more green in their personal lives–and who doesn’t want to lower their utility bills?–but not everybody knows how.

The evidence is just anecdotal, but it seems that the practice is taking hold in a few other places. When I went to a training session this summer at a drafty Victorian in Cambridge, there were about 10 people from other towns and states looking to start their own local chapters.

Weatherizing homes won’t solve all our energy and climate challenges. But while many folks are intent on high-tech (and high-priced) solutions to our energy problems, weatherization is a sensible, low-cost place to start. About 40 percent of the energy in the U.S. goes to commercial and residential buildings and investments in efficiency typically have the fastest payback. Weatherizing a home could cut energy use by as much as 30 percent, according to the Department of Energy, and many steps at are relatively inexpensive.

Even at an event devoted to the potential of solar power–the Solar Decathlon–U.S. Secretary of Energy Steven Chu last week underscored how important energy efficiency is to the country’s energy policy and people’s pocketbooks. In every place they’ve lived, Chu said he and his wife have made a game of trying to cut energy bills in half from the previous owner.

Foam patrol
Well, our little barn raising effort probably won’t cut the homeowners’ bills in half. But for less than $500 in material, a good amount of planning, and a bit of sweat equity, we did pretty well. Every group can set up their own rules, but typically it’s the homeowner who fronts the money for the materials–as well as donuts, coffee, and pizza. They’re welcome to lend a hand as well.

Much of the work we did can be done by a weekend do-it-yourselfer. But your task can be greatly helped by a knowledgeable person or a professional. I always recommend people get an energy audit to help them form a home efficiency game plan. Many of them are free, sponsored by states or utilities, while others can cost about $500 for more extensive work (Go to EfficiencyFirst to find an auditor in your location.)

In our case, a local contractor donated the use of a blower door–a temporary door with a fan and monitor attached to it–to test the air leakage before and after our work. A blower door, which exaggerates the air flow through existing holes, helped locate a few big problems. For example, the frame around the basement door had a gap which was letting in a lot of outside air. The faster air flows up into your house from below, the faster the conditioned air–be it cool or hot–goes through roof.

Our group split up into different teams, focusing on different areas in the house. An electrical group, which was led by a professional electrician, installed compact florescent bulbs and covered up electrical outlets with foam barriers. In the basement, I co-led a team of people who insulated hot water pipes and the hot water heater. A bunch of people fanned out to caulk or foam the spots in the basement ceiling and windows where air seeps in from the outside.

In all the home’s zones, we spotted and filled holes, going through many bottles of caulk and cans of expanding foam. The attic crew covered spots in the attic where air was creeping up, another crew caulked around windows in the living space, while another filled gaps in the basement windows and where the stone foundation meets the wood framing.

Before starting, those many little holes added up to a large area–the equivalent of about two sheets of printer paper. After the weatherizing, the air leakage in one unit was cut by almost 13 percent, which is a bit better than average, and the other by 24 percent, which everyone agreed was a very good result.

The two families living there were clearly very grateful. Homes are chosen pretty much by word of mouth. In this case, we worked with the local non-profit affordable housing organization which has made environmental sustainability part of their plans.

It’s a journey
Although the bulk of the work was done by nonprofessionals, there’s still a good amount of skill required, particularly in the diagnosis. Is there a bigger payoff in putting weatherstripping around the front door? Or should you focus on fixing that door that leads to the attic? Also, there can be many routes to fixing the same problem.

This is where energy contractors are supposed to help. But even before you hire somebody, I still think it’s wise to read up on what’s considered best practices in home weatherization. At the very least, the better educated you are, the more value you’ll get from an audit by asking questions specific to your situation. You could start your own barn raising group if you got expert enough.

There’s a wealth of information online, including the Department of Energy’s EnergySavers.gov Web site. One book I’d recommend for the average consumer is Bruce Harley’s “Cut your Energy Bills Now” but there are many others.

Of course, greening your home isn’t just about plugging leaks–that’s just the cheapest place to start. After that, there are a number of options–water-saving bathroom fixtures, better insulation, or more efficient heating and cooling. For big-ticket items, you can look at solar power or an efficient geothermal, or ground-source, heat pump. I’ve been trying to lower the energy load in my own home for years and I still consider it a work in progress so it’s good to have a long-term plan.

The skills you learn can come in handy whenever you do home improvements like putting on an addition or new floor; those are opportunities to insulate or block air holes. Also, armed with the knowledge of how important air sealing is will keep contractors on their toes. In my experience, electricians and cable installers will blithely drill holes wherever it’s convenient for them.

In the meantime, our local HEET group is looking for more. It’s usually not simple to organize a group of volunteers to do something they’ve never tried before. The work itself is not what you’d call glamorous either. But having worked on a few barn raisings now, I’d say it’s well worth the effort.