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Blower Door Setup, Accurate Measurement and Interpretation of Results
Blower door setup
Accurate blower door measurements start with making sure the house is in winter conditions with all the windows, fireplace flues and exterior doors closed. Good records need to be kept on your blower door setup to ensure repeatably such as:
All those details help repeat the same conditions if another person tests the home out, to ensure a controlled environment.
What if you can't reach 50 Pa in a blower door test?
If the home is very leaky or very large and your blower door can't depressurize to 50 Pa, then you can use the @CFM50 button on the manometer. This will interpolate the CFM 50 for you and it's also a good idea to take readings at 20 Pa, 30 Pa, 40 Pa and the highest Pa you can get.
Interpretation of results
There are several ways you can interpret air leakage results. The method you choose to report will depend on who you are reporting to. If you are doing city weatherization work you will need the MVR and make recommendations on how much CFM is available to seal, or what size exhaust fan is recommended. If you are doing energy audits as part of new construction to meet the Building Code, they may want to see the ACH 50. If you are a home performance contractor wanting to do the contracting work, homeowners won't care about MVR or CFM 50, they want to know the equivalent leakage area and cost saving potential. Knowing your customer will tell you what type of conversions you are expected to do. Many software programs now have built in calculations for your convenience but I've included the links for each calculation below.
3a. Applied diagnostics and troubleshooting