I have a 1958 bungalow, (in Western Canada,) that has attic insulation that looks like cellulose, which has reduced down to a depth of about 2 inches. At some point, someone has placed R-20 batt insulation across the rafters, in an effort to upgrade the insulation. The problem is the dead air space which was left below the batts, to the depth of the rafters, less the 2 inch cellulose fill. As the batts are 24″ widths, and the rafters are mostly, but not all, 16 inch centers, its not feasable to place the batts correctly between the rafters. The house is cold and uncomfortable in winter.
I’ve been told that all thats needed is to lift the perimeter batts and blow some fibreglass fill under them, but that its not necessary to fill the whole empty dead air spcaes below the batts. I don’t want to spend a whack of change on this, and be disappointed. Also, I don’t really want to dispose of the pink batts unless it would be more cost-effective to just pitch them and spray in all new firbrglass.
Any thoughts or advice would be appreciated.
Replies
First, lift the upper batts and find the air leakage sites where warm, moist air escapes from the house and seal them. A book available on the web from Natural Resources Canada (http://www.nrcan.ca) called "Keeping the Heat In" will give you an idea where the lakge is likely to be. They have some other documenst on air leakage control also.
After the airsealing is done, blow cellulose fiber under the batts or slightly over the tops of the ceiling joists where they are exposed. (about 1" higher) Lay the R20 batts back down and add another 3-4 or so inches on top of the batts. This should give you at least R45 or so, not too much R value for the price of fuel these days.
You shoiuld be able to rent or borrow an insulation blower from one of the big box stores like Home Depot. Here in Halifax, if you buy 20 bags of cellulose they lend you the blower for a day- great deal!!!