Several years ago, when I first became interested in the benefits of air-sealing, I enrolled in a Building Performance Institute (BPI) training program that taught me the basics. I later learned a lot more while working on a Passive House project, which called for air-sealing to a very high standard (see "Building a Simple Passive House," 8/11). I now consider air-sealing to be a routine part of every remodeling and new-construction project, and I have a good-sized bag of tricks at my disposal that allows me to deal with a wide range of situations. Some builders may worry that aggressive air-sealing can lead to a building that's "too tight," but that's looking at the problem the wrong way. Rather than deliberately building a structure that leaks uncontrolled amounts of air, I think it makes more sense to build as tight as you can and provide fresh air with a correctly sized, balanced ventilation system.

And while air-sealing isn't a glamorous or sexy job - no one is going to drive by the house you just completed and say, "Wow, they did a beautiful job air-sealing that envelope" - it has an enormous bearing on both a home's energy efficiency and the comfort of its occupants. If you are trying to sell green building, energy reduction is about as green as it gets.

Someone has to do it. Perhaps the single most important lesson I've learned in the past few years is that you can't count on crew members or subs to do their own air-sealing as the job moves along. There has to be someone on the job who oversees all of the trades to make sure the air-sealing gets done, and who is willing to give this role the focus and attention to detail it requires.

On my projects, that person - known to my crew as the air-seal specialist, or ASS - is me. I do as much of the air-sealing myself as I can, working just ahead of or behind others on the site as the situation demands. Doing the job correctly calls for an unbending attitude: I recently had to make one member of my crew - an experienced guy who's been with me for years  and should have known better - remove a just-installed kitchen cabinet when he admitted that he hadn't sealed the pipe penetrations behind it. Neither of us was happy about it, but the result was a tighter, better house.

Testing and Retesting

I don't think it will be long before a blower door is as much a fixture in the back of every good builder's truck as a circular saw and laser level. Unless you know how much a building leaks before you start, you'll never know how much progress you made when you are done. Solid before-and-after figures mean more to clients than a generalized assurance that the building has been air-sealed.

I perform a blower-door test on all remodeling projects before any work has been done. Once the house reaches 50 pascals, I might occasionally use a smoke pencil to home in on air leaks, although the smoker becomes less and less necessary as you gain experience. (From the standpoint of finding leaks, it doesn't matter whether the pressure is positive or negative, although positive pressure is a better choice if you're concerned about sucking mold, dust, or fumes into the living space.)

But the smoke pencil has another use. I like to hand one to the homeowners at the beginning of a remodeling project and go through the house with them looking for leaks. It's easier to sell the job once the client understands just how much expensively heated or cooled air is escaping out the holes. In many cases you can actually hear or feel the air whistling through outlets, baseboards, windows, light cans, plumbing penetrations, and other common problem areas.

I do a second test after rough-in of wires, vents, and plumbing but just before insulation. That way, I can still access most of the leaks if additional work is needed. At this stage, a smoke pencil is very useful to find small remaining leaks. I perform a final test upon completion of the job.

In new construction, I ordinarily perform four separate blower-door tests: after the shell is closed in and the windows are installed; after rough-in and initial air-sealing of the plumbing, electrical, and other mechanicals; after the drywall has been hung and taped; and, finally, when the job is done.