When we bought our house, “sustainability” wasn’t part of our everyday vocabulary. We did know that a 100-year-old house was likely to bankrupt us with heating bills unless we made serious changes. Other than new wiring, no major renovations had been undertaken since the 1960s, a plus since the scary vintage state of the house meant that we could afford to buy it. But we had a lot of work to do if we were going to be both snug and solvent.

My fantasies of choosing paint colors and bathroom tile took a back seat to insulating the walls and attic on a do-it-yourself budget. Soon, friends’ eyes were glazing over as my conversation reverted inevitably to the eccentricities of a folk-built house. Other people might describe vacation plans or the accomplishments of their children; we obsessed about R-value—the quality of conductive resistance that keeps heat from flowing through insulating material. We also needed to block cracks that allowed heat to escape from the house (air leakage), and the drafts that moved cold air through the interior (convection). Energy efficiency always starts with how we address these three issues in walls, floors and ceilings—the “envelope” of the building.

One day at the lumberyard, we got a bit of advice that we named in honor of the man who offered it: the Bill Principle. “Do what you can,” said Bill. “Every bit helps. If you can’t afford the best, settle for good and keep at it.” That turned out to be pretty good advice.

Working room to room as our budget allowed, we used high density fiberglass batts between the wall studs, then added a layer of oil-backed Polyisocyanurate foam, carefully taped at the seams. This brought the insulation to a respectable R-19 and addressed air leakage. In the attic, we achieved R-38 with multiple layers. Our first full winter in the house, we became relentless draft hunters, caulking around the window trim, adding insulation around electrical boxes and installing child-proof plugs in the outlets, all of which made a remarkable difference.

Sixteen years later, we are more aware of the full life cycle of materials, what they are made of and how future generations will maintain or dispose of them. So today we would probably choose cellulosic insulation instead of fiberglass. This green insulating material is 80% recycled post-consumer newsprint. It uses about one eighth of the energy to manufacture as needed to produce fiberglass, according to the University of Massachusetts/Amherst, and uses none of the toxic propellants (or petrochemicals) associated with spray foam—better for indoor air quality, and safer for the people who make it and install it. The U.S. Department of Energy rates it at a higher R-value per inch of thickness than fiberglass. When blown in, it also blocks leaks and drafts, which is great for a retrofit but not recommended for DIY.

We have tightened our building envelope enough to heat almost exclusively with one wood stove, reducing our household fossil fuel use so much, our disappointed supplier told us we’ll never be customer of the year. A solar thermal hot water system is next on the wish list.

The Bill Principle gave us permission to do our best with our available resources while continuing to pursue better solutions down the line. Whenever we feel paralyzed trying to decide which materials are the most economical and environmentally responsible, we remember the wisdom of Bill: Don’t get hung up on perfection. Do what you can, then do a little more. Keep learning, and keep working to make better choices.