# calculating blown in insulation



## donnie leeser (Jul 20, 2011)

How do i calculate how much blown in insulation i need


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## vsheetz (Sep 28, 2008)

donnie leeser said:


> How do i calculate how much blown in insulation i need


Welcome!

A Google of _blown in insulator calculator_ finds this from Lowes, and others:
http://www.lowes.com/cd_Blown+Insulation+Calculator_619120107_


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## AGWhitehouse (Jul 1, 2011)

One point to keep in minid is that without an air barrier, the effective thickness of batten insulation is greatly reduced. You can have R-40 worth, but on about R-25 to 30 will actually be performing. This is due to air currents on the exposed side of the insulation. Figure into the project adding a layer of tyvek on the attic side of the blown-in. If you put it in and staple it before you blow then you can just fill it up. It would be easier to install it before rather than after.


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## parts (May 6, 2009)

Easier still to air seal the attic before installing insulation by foaming and sealing any penetrations around ducts, wires,pipes. Except in very few applications tyvek over the insulation is impractical and would be very difficult to seal and cover completely. Best to use cellulose blown in as it holds it's R value in cold weather and resists air flow much better than fiberglass


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