I've done a bunch of home weatherizing and insulating projects over the years; let me tell you about the worst.

Last week I wrote about "deep-energy retrofits"--strategies for dramatically reducing the energy consumption of an existing house. In northern climates, such retrofits often involve adding a layer of rigid insulation to the exterior of a house. If you're removing the siding to add insulation, this is a great time to provide a drainage layer--or "rainscreen"--before reinstalling siding.

The U.S. Green Building Council just sent out information from a report written by McKinsey and Company about energy efficiency and its role in U.S. mitigation of climate change. Here's what they found:

Starting in the 1970s, following the first energy crisis, major weatherization programs were launched to tighten up American homes. The Weatherization Assistance Program of the U.S. Department of Energy, which focuses on low-income homes, has weatherized some 6.2 million dwellings, reducing energy consumption by an average of 32%, since its inception in 1976.

As houses get tighter, they becaome less able to 'breathe' on their own -- they need mechanical ventilation. Put another way, energy efficient houses deserve healthy indoor air.

The first question I usually get when I start talking about insulating and buttoning-up houses is, "Won't my house be too tight?" It's a very logical question.