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  1. #11
    Join Date
    Dec 2007
    Location
    MN
    Posts
    455

    Default Re: Adding even more attic insulation

    Holey mackeral.
    I'm with Canuk.
    There's no way that theory would work in MN. Considering how cold it's been lately I'm happy to have R40 in my attic. Besides, in the big scheme of things insulation doesn't cost a whole lot.

  2. #12
    Join Date
    Dec 2009
    Location
    Ithaca, NY
    Posts
    2

    Default Re: Adding even more attic insulation

    Thanks for the great discussion on my original query. I also contacted Owens Corning and they concurred that there would be some slight compression of the lower levels, but never-the-less their would be a net gain in adding another layer of insulation.

    I'm with the extra insulation folks--the cost is fairly low if I do it myself and over the long haul it will pay for itself.

  3. #13
    Join Date
    Aug 2007
    Location
    The Great White North
    Posts
    4,045

    Default Re: Adding even more attic insulation

    dll --- good stuff
    "" an ounce of perception -- a pound of obscure "
    - Rush

  4. #14
    Join Date
    Aug 2009
    Posts
    62

    Default Re: Adding even more attic insulation

    Yup I've been considering it on my townhouse in mild, mild Maryland (well, mild compared to MN, we only get 0F days maybe once every two or three years and single digit only a couple of times a winter). It's 2x4 truss construction for the roof with about 6 inches of lose fill rockwool insulation taking in to account compaction over time (wholely inadequate). I put in R13 batt insulation opposite the direction of the trusses about a year and a half ago (about $110 of insulation) and that seemed to help out a fair amount. Its probably only around R-30-35 total now. I've been considering adding a layer of R-19 on top of what is there now since the cost would still be around $100-130 total. The only thing stopping me is I know now I am probably only going to be in my house for maybe 2 more years tops and there are a number of other things requiring my time and attention.

    I did throw a little extra insulation up over my back bedrooms recently. After reinsulating the overhang of those back bedrooms so that it was done properly I reused the bit of R-30 that had been in the floor of the overhang in the attic. It was only about 35sq-ft of insulation but I stripped it in to 3rds so I covered about 100sq-ft of attic with an additional R-10 cover. Its not much, but better then just throwing out the insulation.

  5. #15
    Join Date
    Feb 2010
    Location
    Eastern MA
    Posts
    75

    Default Re: Adding even more attic insulation

    Adding more of what you have will only get more of what you already have - a cold building. The problem is air infiltration. All the leaks into the attic and warm air on the attic side of the sheetrock rising through the fiberglass. Actually the warm air doesn't have to go through the fiberglass when it has all the gaps around the edges of the fiberglass. You need to seal the ceiling first. In NY you have a great program through NYSERDA Get a contractor who is BPI (Building Performance Institute) certified who will do the job right. There is much more to this than just adding insulation.

  6. #16
    Join Date
    Mar 2009
    Posts
    1,387

    Default Re: Adding even more attic insulation

    Howdy before you add more insulation first consider adding silicone caulk around the ceiling light fixtures to stop air infiltration into the attic. Then look for dirty insulation in the attic as the dirt is a sign of air infiltration spray cans of foam around the penetrations wires and pipes is a great way for small cost to reduce the heat loss. Then check with you areas building dept is R48 what is recommended? if your agile and plenty of room then adding another bat perpendicular to existing is a good choice but Blowing in fiberglass or cellulose is easier and i'm always for easier. Just make sure any soffit vents are not blocked and bone up on clearance around any chimney pipes to avoid fires first..

  7. #17
    Join Date
    Feb 2010
    Location
    Eastern MA
    Posts
    75

    Default Re: Adding even more attic insulation

    If you go the cellulose route you need to seal every penetration into the attic. Around chimneys with sheet metal and fire approved caulk, along every partition top where the sheetrock attaches to the wall framing, enclose every recessed light with an airtight box made of sheetrock that has a 3 inch space to let the fixture not overheat. You need to provide dams at the eaves to keep the cellulose in place and proper vents to make the air go above the cellulose.

    Cellulose is not an air barrier and you need to have one. Air infiltration into the attic is a serous problem and porous insulations like fiberglass and cellulose do not stop it.

    For this much work, I think foam is easier and more certain to do the job right.

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