A blower door test can be a powerful tool for energy audits, allowing the auditor to pinpoint areas of air leakage that can contribute to high heating and cooling costs, uncomfortable drafts, or poor indoor air quality. It is also a key requirement in many building codes and energy certification programs such as IECC, spray foam insulation, and Zero Energy Ready Homes.

Understanding Blower Door Test Results: What They Reveal About Your Home

The basic system consists of an expandable metal frame that fits tightly in an exterior door or large window; a nylon panel attached to the frame and used to make the building envelope airtight; a calibrated fan installed in the nylon panel and used to push air out or into the structure; and a pressure measurement device (manometer or pressure gauge) that measures the pressure difference between the inside and outside of the building. The fan speed and manometer size can be adjusted so that the desired indoor/outdoor pressure differential can be maintained. Most modern blower doors have a computer or data acquisition system that allows the operator to control the operation, while recording the results. The most important piece of information provided by a blower door test is the CFM50 measurement, which gives the amount of air passing through the fan per minute at a 50 pascal differential between indoor and outdoor pressure. The resulting ACH50 value provides the auditor and home owner with a measure of how airtight the building is.

Temperature and barometric pressure affect both air density and viscosity, and must be factored into calculating the CFM50, ACH50, and other blower door metrics. The most accurate way to calculate these adjustments is with software packaged with the blower door equipment, but it can also be done manually.

NextGen Spray Foam Insulation
Kila, MT 59920
(406) 871-3729