Home energy audit, Blower door test
November 17th 2010 11:25
Blower door testing is the most practical way to predict energy savings from air sealing methods. I have just recently been certified by B.P.I. (Building Performance Industry). I went to a two week workshop and was tutored on a very informative way when it comes to air leakages in your home. I have bee in residential home construction for 30 years and in this workshop I seen things that I have overlooked for years.
Like your lungs blowing pressure to keep the beach ball inflated, the blower door pressurizes your home by blowing air in or depressurizes the home by sucking the air out. Depressurization, which creates a vacuum indoors, is the most common procedure because air comes in through air leaks, allowing you to feel and locate the air leaks in your home. The combined area of the building leaks and the pressure difference between the indoors and outdoors determines how much air the blower door moves. The air flow is measured by CFM( cubic feet per minute).The standard for measuring a homes’ air leakage is the air flow through the blower door at 50 pascals of house pressure(CFM50)
Prepare the home with the following steps:
• Closing windows and storm doors.
• Opening all interior doors.
• Disable heaters and water heaters by turning down their thermostats.
• Covering ashes in wood stoves and fireplaces with damp newspaper to prevent them from being sucked into the home.
• Shutting fireplace dampers, fireplace glass doors, wood stove dampers, and wood stove air intakes.
The blower door operator slowly brings the house pressure to 50 pascals. This is usually preset with the doors gauges before he begins. With the house pressure at 50 pascals the operator notes the CFM50 number from the digital air flow gauge. This is where he begins to look around the home with a smoke generator to help find the air leaks in your home. I promise that you will be amazed where and the amount of leakage occurs.
There are several common factors to help to determine the amount of air leakage you may have in your home. This is a little technical but maybe you will understand enough to help you understand the
Importance of a test of this nature.
1. The 50 Pascal Airflow Rate: a blower door reading expressed in cubic feet per minute (CFM50), is the actual flow measured at 50 pascals of house pressure.
2. The 50-Pascal Air Change Rate (ACH50): a blower door reading expressed in air changes per hour at 50 pascals. This is calculated by multiplying the CFM50 by 60min/hour and then dividing by the house volume in cubic feet.
3. Natural Air Change rate (ACHnatural): natural air change is expressed in air changes per hour.
If all of this sounds a bit overwhelming the home energy auditor in your area will know just what to do with all these numbers and formulas. That is why it took me two weeks in a workshop that the technical college where I am employed sent me to. If you are wondering where to find an energy auditor check with your local courthouse or utility company. This will be money well spent!
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