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Old 07-14-2008, 12:23 PM   #1
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Low Slope


I have a bungalow with 3/12 low slope roof, gable style no hips ~1600sqft, north and south side.
Roof has 40 year old ashpalt/gravel now getting leaks on south side.
North side has attic, soulth side is high ceiling so 6' rafter space only.
I am in Edmonton, very cold winters, very hot summers, downpours, moderately high winds.
I want to scrape the roof, remove the roof deck on the south side and insert 5" of rigid foam insulation (R25) and leave ~1 in air flow from soffit to attic. Put air handler(s) in side wall of attic.
Want to use Ice & Water Shield with organic shingles.




1. Any thoughts? I don't have a lot of air flow space (<1"), I could raise the roof from a 6" space and add ~4".

2. What is the best shingle brand.
I have not seen good reports on IKO (RoofMart). What about RAMPART from Home Depot?

3. What is the best rigid foam insulation - Owens Corning FormularPink (1"=R5)

4. Is OSB the preferred roof deck material?

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Old 07-14-2008, 08:24 PM   #2
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Low Slope


We're in Montreal and by the sounds of it we have similar houses; I am starting to look a ound too as although we don't need to this year, soon we'll need to do something about our cathedral ceilings. People in this neighbourhood have added another roof to their existing ones, one even has a metal roof, so it's an idea whose time has come.

Is this what you're doing? or is that just an option? adding another "layer" essentially making your 6" a 10" thick roof. What insulation is there now under the sheathing and below the insulation...what vapour barrier is there? I trust you'll be taking that out too.

If you have 16"OC joists, what are you going to do, cut the EPS to fit?

Have you looked into sprayed foam, closed cell? You'd get around R45 with that.

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Old 07-14-2008, 10:49 PM   #3
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Low Slope


It sounds like you have received good advise from the previous poster so far.

John K is from the Land of Back Bacon too, so, maybe he will chime in with his climate related experiences.

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Old 07-15-2008, 12:03 AM   #4
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Low Slope


check out soythane.com for closed cell foam insulation,almost R-7 per inch,and installed properly seals the house off from the attic as well.which in canada is considered one of the more important requirements
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Old 07-16-2008, 07:36 PM   #5
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Low Slope


Thanks for the info. Presently, rafters are 16"OC, vapour barrier install with 2" pink fiberglass bat. Then air space for ventilation.

It has been suggested to add a new roof structure onto the existing and use metal with greater slope. I do not like adding on to the roof (permits), do not like metal (expansion & cost/value).

I now think filling the 6" void completely with insulation is better that leaving an air space for ventilation. I would prefer to use polyurethance foam (~7.50/sqft and needst o be applied 3' at a time - 2 visits 24 hours apart) but will evaluate that $5000 against either 1. cutting and sealing in rigid or 2. Roxol bats each at ~R5/in.


Quote:
Originally Posted by ccarlisle View Post
We're in Montreal and by the sounds of it we have similar houses; I am starting to look a ound too as although we don't need to this year, soon we'll need to do something about our cathedral ceilings. People in this neighbourhood have added another roof to their existing ones, one even has a metal roof, so it's an idea whose time has come.

Is this what you're doing? or is that just an option? adding another "layer" essentially making your 6" a 10" thick roof. What insulation is there now under the sheathing and below the insulation...what vapour barrier is there? I trust you'll be taking that out too.

If you have 16"OC joists, what are you going to do, cut the EPS to fit?

Have you looked into sprayed foam, closed cell? You'd get around R45 with that.
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Old 07-16-2008, 08:14 PM   #6
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Low Slope


I kinda think that ventilation space above the insulation is pretty important and I know that if tied in to a proper ridge vent or several gooseneck-type vents (about 6 of those), you'll' have the best of both worlds. Just filling that whole cavity with, say, Roxul may give you problems down the road when your covering degrades prematurely.

But only you can make those decisions as it all ties together with how long you plan on owning the house, and your budget. A couple of guys can do it bit by bit, doing as much as you can in one day annd saving some scratch. But then if thats your plan, I'd look into adding a new roof since you're up there and getting more bang for the buck.

Just my 2 cents; I'm no pro or anything...

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