# Attic Project – Venting and Insulation



## TrapperL (Jul 23, 2011)

I'd suggest taking the tour at building science.com. They pretty much can advise you what is the best for your particular needs and environment. If you get a chance to go to one of their seminars, they are incredibly interesting.
http://www.buildingscience.com/index_html


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## spaceboy (Sep 2, 2011)

TrapperL said:


> I'd suggest taking the tour at building science.com. They pretty much can advise you what is the best for your particular needs and environment. If you get a chance to go to one of their seminars, they are incredibly interesting.
> http://www.buildingscience.com/index_html


 
Will do - im sure i will have some additional questions after.

That said - I sill think this is a very opinionated subject and not so sure there is really a "correct" answer. 

Also - not sure if it helps... but i have added a photo of the attic.


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## spaceboy (Sep 2, 2011)

So here is what I have decided to do (i hope someone in the same situation finds this helpful). I have researched, researched and researched more... 

Taking costs and overall effectiveness into consideration - here are my thoughts and what i plan to do. 

Fiberglass has less r-value per inch than rigid foam. Spray Foam would require me to install the Durovents to the roof deck (extra cost) and to get to an appropiate R value - I would have to somehow extend out my rafters as they are 2x4's.

It's not recommended to either have the insulation in contact with the roof sheathing, or to compress fiberglass. 

What is the solution you ask... Not sure if this is right... but this is the best I can come up with:

Rip pieces of 2" or 2.5" rigid foam to fit between the existing rafters
- Keep the foam flush with the lower edge of the rafters leaving an airspace @ the roof sheathing (removes the need for the durovents)
- Caulk and Tyvek-tape the seams (can even tyvek wrap the entire interior if you like - i personally think this is overkill.) I have also thought about spray foam to seal but cant figure a way to make it flush and the added cost, in my opinion, cant be justified. 

Next, apply full sheets of 2" foam to the whole ceiling, using long screws and washers. 

Now, being aware of where the rafters lie under the foam, chalk out lines 16" on center from the peak to the plate, perpendicular to the rafters, parallel to the ridge and side walls. 

Next, using long screws into the old rafters, install 1" furring strips along these guide lines. To this you will attach the drywall or whatever finish.




Overall r value will be about 28, but possibly even better because of the 1" dead air space with the furring strips, and the fact that the ceiling is thermally isolated. 

I plan on starting this sometime in Nov and if anyone is interested - I can post progress and photos if you like.


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