Energy Retrofit for an Old House

What's the best way to add enough insulation to an old house to really make a difference in how much energy we use? I know that cellulose can be blown into the walls, but somehow that seems inadequate given the high cost of energy these days. Is there a more radical approach that won't wreck the house in the process?

Retrofitting an old house so it approaches the energy performance of a new one is tremendously challenging. Blowing cellulose or fiberglass into wall cavities is a big improvement over no insulation at all, but it's really only a start. Many older homes would benefit from more aggressive measures, especially as the price of energy continues to go up.

Other than cost (these renovations can get expensive), one of the biggest obstacles is finding a way to add lots of insulation to exterior walls without destroying all the detailing that makes so many old houses special in the first place. Gutting the house provides the opportunity for many upgrades, but when that means tearing out old plaster and trim, the cure almost seems worse than the disease.

Even if you can find a way around that problem, another major question is how you'd cope with the noise, dust, and many other inconveniences that go along with a major interior renovation.

There is another way: Make the energy improvements from the outside of the house.

Cador Pricejones, a carpenter and project manager with a Boston-area renovation company called Byggmeister, recently undertook one such project. He owns a 1914 two-family home in Somerville, Massachusetts. It had cellulose insulation in the walls but still used a lot more energy than he would have liked.

So he added a second skin to the house, starting with new studs applied directly over the old siding. He filled the exterior wall cavities with closed-cell polyurethane foam, added new windows and siding, and repainted the house.

The interior of the house was essentially untouched. Pricejones was able to preserve the original trim along with other architectural details, and the house looks essentially the same from the outside. But what a difference in comfort and energy consumption. All the air leaks that plague most older homes are gone and the extra insulation should reduce heating bills by 60% or more.

Pricejones was lucky to have roof overhangs that were wide enough to handle the extra exterior wall, at least in most places. It's not a solution that fits every house, and it's one that takes a fair amount of expertise. But with the right outside help available, it's an option worth considering.

There's every reason to put an old house on a strict energy diet. Heating and cooling costs shouldn't drive people out of their homes, and the planet will thank us for burning less fossil fuel.