Attic insulation

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Posted by: from Windsor
3/12/2012 at 7:18:20 PM

My home was built in the 1950's and I am planning on adding insulation to my attic. The previous owner had already added a layer of R20 and I am going to add another layer to bring it up to R40.

On inspection I noticed that between the last joist and the outside wall on both ends of the house there is no insulation whatsoever. I can barely reach this area when lying on my side but I am able to push insulation batts into the spaces without blocking the ventilation, however there is not enough room to work on installing a vapour barrier.

My question is, would I create a problem if I was to push the insulation in without a vapour barrier?

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Date/Time3/13/2012 at 7:15:15 PM

Vapour barriers go on the warm side. That is in your attic it should be under all your insulation. You should not have any on top or in the middle. You can block the ventilation in the corners as long as you have a continuous sofit vent around the rest of the house.

Insulation is cheap and gives you the biggest return on investment in an attic. So why not load it up to R60 or higher, there is no such thing as too much in an attic.

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Date/Time3/14/2012 at 11:58:05 AM

Hi John, In general, if you have sufficient attic ventilation, you could go ahead and install additional insulation, James is right - the more the better -current minimums are R50.

You should also seal all wall / ceiling penetrations as well as possible to ensure no humidity is getting into your attic. This can be done with gaskets on the plugs and switches, and spray foam / caulking around light fixture boxes. Make sure your attic hatch is insulated to the same level as your attic and well sealed. The drywall or plaster is actually a very effective air / vapour barrier by itself, especially with a few coats of paint on it. It is the penetrations that you have to worry about.

If you want to do some research on it, do a search for "building sciences corporation" They have some great, science based info on best practices for building envelopes.

Good Luck with it!

Jim Kuzma

Kettleby Handyman Services

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John in Windsor
Date/Time3/22/2012 at 5:29:47 PM

Thank you both for your input. I guess I would be better to bring it up to R50 at least.

Thanks Jim for the info on the paint being a good vapor barrier in itself, my old house must have quite a few coats on over the years.


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