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  1. #1
    Join Date
    Mar 2008
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    Blower Door Test Results and attic insulation questions

    I just had an energy audit done including a blower door test. The result was 1558. The contractor expected 1800-2000. So it seemed better than expected. He also mentioned a value of less than 603 would require mechanical ventilation. I was wondering for a 1962 built house that is 1250sft is 1558 a good number?

    I was having the company do a quote on more attic insulation. They are quoting to do the following:
    1. Insulate all attic area to a minimum of R50.
    2. Air seal all penetrations and thermal bypasses, including but not limited to inner wall connectivity and mechanical, flue, electrical, and plumbing penetrations.
    3. Seal all recessed fixtures by attaching and sealing insulated boxes from attic side.
    4. Insure adequate soffit/attic communication by verifying proper soffit ventilation .
    5. Build insulated/air sealed box over drop down stairs.
    6. Air seal flue area with high temp caulk.

    The cost was over 3 times higher than what I would expect to just have someone come in and blow insulation. Is all this sealing really worth it, or am I being taken for a ride? Thanks


  2. #2
    Join Date
    Aug 2004
    S.E. Pa
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    Cool do your homework

    Be very careful with all these weatherization measures. Unguided, you can make the home unhealthy or down right dangerous.
    BTW, the cost is in the man hours of all the tedious air sealing--not blowing cotton candy in the attic.

    A few points to consider: If you have non-IC rated light fixtures in the attic and put a box over them, you can burn the house down. Replace the fixtures with ICATs--Insulation Contact Air Tight cans.

    Other ceiling penetrations can be sealed with UL 181 duct mastic

    Any hatch or attic stairs should be gasketed and insulated to meet the rest of the attic's R-level.

    Before you caulk around heating vents and chimneys, you must ascertain if it is allowed by any product listings. Some mfrs. rely on cool air movement aorund their vents so it doesn't present a fire hazard. Caulking may actually present a fire hazard. You would need to identify the brand vent you have then contact them. For masonry chimneys, the code specifies how to firestop and fireblock around them.

    All air ducts should be sealed with a UL 181-a/b FX duct sealing mastic.

    Make sure any bath exhaust fans are ducted straight to the outdoors and not into the attic. Ditto for clothes dryers.

    The building code is your resource for these measures as it has become more prescriptive. Ask your contractor what code applies then ask him to show you his copy of the current code and the relevant sections. Even the local Building Dept. often is not up on the codes they inspect to (being polite here).

    Then when it's all done, you need to get a qualified technician in there to perform combustion analysis, draft intereference and CAZ testing and a comprehensive HVAC system analysis.

  3. #3
    Join Date
    Dec 2007
    Cedar Grove, Wi-Sheboygan
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    Thos enumbers you have for leakage are actually pretty good for the year home you have. I was recetnly told that average homes built today have a leakage rate or are rated at aroud 2200-2300 leakage rate so your home fall way below the average construction of today standards. My leakage rate cam in at around just under 2300 for my home with 1600 sq. ft. which is right at the threshold of new construction of today, and I have alittle more sealing to do yet and will have another blower door test done once it's all complete.

  4. #4
    Join Date
    Sep 2008
    New York
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    the numbers 1800-2000 or 2200-2300 don't really mean anything unless the house -volume, location, height, and exposure to wind are included. If they said "a value of less than 603 would require mechanical ventilation" a safe and efficient number may be around 700-800cfm@50. So with a test result of 1558cfm@50 you may be exchanging almost 50% more outside air (hot or cold) than needed. this can result in a pretty good savings. They should be able to supply you with an estimate on the saving you could see.

    and as hearthman said
    "Then when it's all done, you need to get a qualified technician in there to perform combustion analysis, draft intereference and CAZ testing and a comprehensive HVAC system analysis."

    That is good advise.

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