The Blower Door

The blower door is a tool that the general public has never heard about. It's a tool designed to test a home for "leakiness." Being The Energy Guy, I can use it; tell you how it works in layman's terms - but don't ask me "exactly" how it works. I'll leave that explanation to The Science and / or Math Guy (or Gal).

The blower door is an expandable frame that sets up in a major exterior door. A tarp is placed over it to block air movement, and a fan is inserted into a large hole. A gage is connected to 2 hoses - one to the outside (measuring the outside pressures) and one to the inside (measuring the home's environment.) With all this being said, the fan is turned up so that it is as close to and steady at 50 pascals. What's a pascal, you ask. See above - it's a unit of measurement that was named by The Science Guy. At this 50 pascal measurement, a reading is taken showing how many cubic feet per minute (CFM) are leaving the home (the fan is blowing outwards). In effect, it's a simulation of a 20 MPH wind against the shell of your home, forcing it to leak.

While this is occurring, you walk through the home in search of air leaks. A smoke puffer or eyes/feeling can be used to find the leaks. This is the first step to determining how leaky a home is. An example - a home registers 4500 CFM50 (cubic feet per minute at 50 pascals). This is approximately equivalent to a 4 1/2' X 4 1/2' window in your wall open year round. All homes require a certain amount of breathing - but this reading is very poor. Optional air sealing takes place at 2,750 CFM50. If you are at that target, you may or may not need to air seal. There's also building tightness limits - but we're straying wayyy off subject. There are various percentages that different levels should be reduced by - 50% on down. Our company just completed a home and the final blower door reading was 4,034 CFM50 - and we were happy. The original BDR was 8,164...

Proper air sealing should be done prior to insulating - for without air sealing, insulation is just a filter.

OK, The Energy Guy has a tendency to ramble - it must be getting late.

COMMENT REPLY: Of course the first question I received has nothing to do with weatherization. However, I will answer any question or respond to any comment I receive. Anonymous Guy (or Gal) wants to know where I got the graphic of The Energy Guy and how it was inserted in the template. Well, I have a good friend - The Graphics Guy, and he purchase the photo from a stock company (for $1, I think). The guy had hair, so Graphics Guy shaved him clean to better reflect me, The Energy Guy. Then he used his super powers to input it - meaning I have absolutely no clue how he did it, however he said it took a couple of hours to do the entire guy.

Next Topic: Air Sealing, Part 1 (and any replies to comments posted).