Originally Posted By: kleonard This post was automatically imported from our archived forum.
I had a client ask me if it’s ok to insulate between the rafters.
The house was built in 1920 and has a stairway leading up into the attic. She wants to turn it into a bedroom and insulate between the rafters.
Would this be ok since there would be no ventilation?
Would moisture be a problem with the sheething?
should a vapor barrier be installed and on what side?
Originally Posted By: Guest This post was automatically imported from our archived forum.
Hi Kevin,
I'm assuming that it's going to be a cathedral style ceiling. There are two common ways to ways to approach the situation.
If fiberglass batts are to be used (or blown in fiberglass or cellulose) a provision to keep it away from the roof decking must be made to allow for ventilation to keep the roof cold. They make Styrofoam spacers for this purpose, or it can be site made using 1/4 plywood or some inexpensive material. A gap of an inch and a half is desirable. The vapor retarder should be toward the heated space. This method requires venting at the eave and ridge with a continuous path between them.
Another approach would be to fill the cavities w/ spray foam. Two types of foam are available, open cell and closed cell. Icynene is an open cell foam and some feel that the use of a vapor retarder is necessary with this foam, again, the retarder should on the heated side of the insulation.
Closed cell foams like some urethanes do not require the use of a vapor barrier.
Make sure your client resists the urge to use recessed lighting as it is difficult to detail properly and creates a violation in the vapor barrier and insulation.
All this applies to a home in a heating climate.
Originally Posted By: gbeaumont This post was automatically imported from our archived forum.
Hi Kevin,
I did the same job on my own home 2 years ago, just putting insullation up into the rafters is not a good idea due to your suspected ventilation problems.
These older attics normaly have gable vents, which of course will be blocked of if the attic is to be turned into habitable space, so you will loose the ventilation that the home was designed with.
the only way to insullate is to fit continuous soffit & ridge vents, and link them under the insullation with an air gap (I used the pink "styrofoam" type) then insulate over them with the moisture barrier facing the warm side, believe me it's allot of hard work on an older home and breathing in 80 years of dust is no fun.
Originally Posted By: jonofrey This post was automatically imported from our archived forum.
I agree with Gerry. If there is no ventilation of the roof sheathing underneath, you are asking for moisture problems and premature failure of the roof covering.
Originally Posted By: gbeaumont This post was automatically imported from our archived forum.
Hi to all,
Chad, my apologies, I had not seen that you "beat me to the draw !!"
In the light of that my last post should have read:
I agree with John agreeing with me agreeing with Chad   
