|
|
Blower Door Diagnostics
The blower-door uses a pressure gauge, usually digital, which displays pressure and air leakage figures in terms of Pascals (Pa) of pressure and cubic feet of air per minute (CFM), which can then be interpreted by the inspector as to the relatively leakiness of the building.
Tightly constructed new homes may have a CFM50 number of 0.5 per square foot, so for example a 2,000 SF house (including basement) could be 1,000 CFM50. Most Energy Star - Certified homes we rate are between 0.25-0.5 CFM/Square Foot. You can also hear about Natural ACH (air-changes per hour) when talking about indoor air quality. Typically code-built new homes will rate around 0.50-1.0 ACHn. Older, poorly air-sealed homes, with no weather-stripping may have readings higher than 1.5 ACHn. Energy Star and other high-performance homes will be less than 0.35 ACHn, and at the tightness level mechanical ventilation is highly recommended. When a blower-door is used in conjunction with an infrared camera, much greater detail on air-infiltration and insulation performance, or the lack thereof, can be seen. See our Resources page for more on how these tools are used together.
|
||||||
A blower-door is a very useful building diagnostic tool that is used to quanitfy air leakage and differences in pressure in homes, offices, and any other heated and cooled buildings. While the blower-door is running, a pressure-pan can be used to test for duct leakage in specific supply and return registers throughout the building. (Pic below shows a pressure-pan test)
The most commonly used way for building-performance professionals to judge the relative "tightness" or "leakiness" of a building, with respect to other similarly-sized buildings, is CFM@50 Pascals. This is the total volume of air in a home that is turned over in one hour with a pressure difference from inside to outside of 50 Pascals. This simulates roughly 20 MPH winds hitting the house from every angle, at the same time.