We recently had an energy audit for our house and learned a lot, including:
- The most of the corners of the house were never insulated the first time
- Our bulkhead door leaks like a sieve (maybe that’s why I can see light through it :-)
- The attic door and whole house fan let in a lot of air
- The chimney damper is pretty useless in terms of insulating
- Air pours into our basement through the sill and old windows
- Most of our windows still need to have caulking around the edges — air is getting in
- All the leaks result in a complete air exchange about once every 70 minutes in winter
How the Audit Worked
There were two parts: a “blower door test” and an infrared camera inspection (the actual reports are linked below).
The blower door test basically is a way to create some suction of air out of the house with a sophisticated method of measuring air infiltration, or how well sealed your house it. One measure is air changes per house (ACH) — a house does need some fresh air from outside, but the target is something like 0.3 ACH — our house measured an average of 0.65 ACH, and in the winter when windy and colder the estimate is 0.87 ACH (about one change every hour and 10 minutes).
The blower door rig fits in the front door of your house, covering all but a hole sized for a special fan. The fan and some small air-tubes are hooked to a control unit, which runs the tests and measures how hard it has to pull to create a certain amount of vacuum in your house — the harder it has to work, the tighter your house. It runs for about 20 minutes at various settings, and sends the results to a computer when done.
The infrared camera can “see” heat and cold. Hot areas are red, cold are blue.
Our house was constructed around 1920 — in order that the house doesn’t move, all the corners have diagonal “wind braces” from floor to ceiling, in additional to the usual vertical wooden studs (when plywood sheathing replaced boards, wind braces became unnecessary). We had our house insulated with blown-in cellulose insulation several years back — they take off some of the siding, drill holes in the sheathing and pump the insulation in under pressure, one hole for each 16" stud bay. But the insulators missed every exterior corner because the wind-bracing. This is very evident in the infrared picture.
If you look closely at the IR photo, you’ll also see that there are vertical lines in a lighter blue — these are the wooden studs in the wall, which shows that wood is not a good insulator.
The third part of the inspection was a walk-through while the blower was running. I could feel the draft blowing up from the basement as we walked down. Flemming, our auditor, used his IR camera to locate problem areas, then took an IR photo and a matching regular photo. He also had a can of “smoke” that he sprayed in certain areas so that I could see how much wind was blowing. When the fan was running, it produced almost 8 ACH (about 10x more than normal), but still, there was a lot of air flowing.
Part of the report calculated a potential savings of more than $300/year if all of the items are addressed properly.
I was properly motivated, to say the least.
How to Address the Findings
We have been given our marching orders on what to fix, and how. Some of the items any home owner could do, including:
- Spray foam around the leaky sill in the basement
- Caulk around windows
- Seal other areas where cold air is leaking up from the basement
- Improve weather-seal on our kitchen door
- Buy a “Chimney Balloon” to block air-flow through the fireplace
There are other tasks that require carpentry or other specialized skills, including
- Build a box to cover the whole-house fan in the winter
- Build a cover for the attic stairs
- Install a regular (exterior) door at the base of the stairs to the bulkhead door
- Insulate the areas missed in the first round
I have a guy coming over this afternoon to do an estimate on the insulation (and maybe the other items). Cooler still, it turns our our fuel company, NationalGrid, is offering a 75% rebate on the cost of insulating, and there are some federal tax credits available, as well. Wow!
Here are the reports from our energy audit, from InfraredDiagnostics. They are both PDF files. Note, the IR file is 2.7MB.