Warm (un-vented roofs) in Minnesota
sweetlake
| Posted in Energy, Heating & Insulation on
My father in law is remodeling his house here in in Duluth, MN. The second floor is gutted to the rafters and he intended to have 3″ spray foam (closed cell) applied to the roof deck and fill in below with dense pack (I recommended this to him). The local inspectors office told him there is no allowance for unvented roofs in MN, I looked up the minnesota code and section R806.4 of the IRC is deleted by the state. The foam guy is scratching his head and I’m the idiot SIL.
My question is: Are there code approved warm roofs in Minnesota and what do we need to do to comply? I understand the building science, I don’t understand the state deleting that part of the code.
Replies
There is usually a provision "or as the code enforcement official deems appropriate" or something close. Had the same problem in the DC area with a potemtial customer. Five years ago I did a job in Garratt County MD and got the building officials to write a variance. You must still get the required R value. 2X6 roof rafters will get you R-38 of closed cell.
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That is EXACTLY why they don't allow warm roofs.If the roofs where warm you would end up with nakkid roofers.Just thing of frenchy.BTW, I think that frenchy has a warm roof and he is in MN..
William the Geezer, the sequel to Billy the Kid - Shoe
There is a possibility of an amended application:
Seems kind of strange that the state appears to care more that you are likely voiding the shingle warranty than anything else.
http://www.ci.minneapolis.mn.us/mdr/docs/hotroofventilation.pdf
"The Minnesota Building Code (IBC section 1202.2) requires ventilation of enclosed attics and enclosed rafter spaces. A minimum of one inch of air space shall be provided between the insulation and the roof sheathing.
Alternates to ventilation (hot roofs) require an explanation of need and explanation of how the project design works to minimize moisture passing into the insulation space.
The manufacturers warranty for the roofing and roof sheathing may be voided when the roof is not ventilated. Unless documentation is provided showing that the existing roofing is warranted for an unventilated roof, an acknowledgement is to be signed by the property owner stating that he/she recognizes he/she may be waiving any roofing warranty."
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I happen to be from Duluth too, and I will say that you are fighting an uphill battle. We did a few hot roofs prior to the change, but were told flat out by building safety that no more hot roofs would be allowed.
I think your best option is to give up the battle and ventilate it. You could put in cardboard vent chutes and spray foam against them instead of the roof deck.
Thanks guys, We're looking at a metal roof, maybe that would satisfy the state. Duluth's building safety is not very flexible.
Or you could improvise. fur out the top of the roof deck with 2x2's and sheath over the whole thing. Of course this is another expense but you'd be in compliance and still have the interior space looking the way you want.
Even on a remod?
What was there before & was it vented?
Joe H