[Greenbuilding] roof venting

[RT]

Clarke;

I trust that you would do a competent job of air-sealing and building a  
good roof but $#!+ happens and  water  in all of its forms is amazing in  
its ability circumvent/overcome humans' efforts to exclude it from their  
structures.

Low slope, unventilated  I-joist  roof in a heating climate in snow  
country ?   I'd say that's like playing Russian Roulette with five bullets  
in the magazine of a six-shooter.

One scenario that could throw a curveball into the good intentions:       
-- large accumulation of wet snow on the roof during an unusual weather  
event causing excessive deflection in the relatively skinny  I-joists  
stressing the painted taped joints in the drywall compromising the  
integrity of the interior air barrier. Same snowfall results in ice dams  
and or ponding subjecting the roof cladding to conditions that it was  
never intended to deal with.

That's just one possible scenario leading to moisture intrusion into the  
framing cavity jammed full of Roxul.    The Roxul would be fine...  
eventually...  once the moisture drains out of it and gets cooked off  ...  
but the gumboard webs of the I-joists and gumboard roof sheathing would  
likely be an unholy mess of black flakes in time.

As that wonderful woman Meryl Streep once shouted out , after she and her  
two co-stars had belted out some disco-era tunes while the movie credits  
were rolling "YOU WANT MORE ??!!!"



On Sat, 21 Jan 2017 13:02:05 -0500, Clarke Olsen <colsen at fairpoint.net>  
wrote:

> I am building a 750 sqft building with two single plane (shed) roofs,  
> using 12" I joists @ 3/12 pitch.Can we just stuff that 12" with Roxul,  
> or is ventilation needed?


-- 
=== * ===
Rob Tom T6015O
Kanata, Ontario, Canada

< A r c h i L o g i c at Y a h o o dot C a >

(manually winnow the chaff from my edress if you hit "Reply")
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