Roof vents

Old 04-25-09, 08:23 PM
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Join Date: Mar 2009
Location: Sarnia, Ontario
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Roof vents

O.k this is one of the last questions I have. I am curiouse about roof vents. I don't believe there mandatory as I've noticed soom roofs have them and some don't. I know they increase the life of the shingles by lowering the underside/attic temp. Heres my question I take ownership of my house this week and plan to reshingle very soon. The house does not have any vents at this point. Its a simple roof front section and rear (house is a three level back split) ridge vent will be a lot of work I will probly use a high quality square roof vent but how many would be needed and any other considerations needed or is it just measure location cut hole install vent and shingle over. I will probly place a adheisive sealant on bottom side of flange during installation as a extra leak precaution.
Old 04-26-09, 02:23 AM
Join Date: Aug 2008
Location: Ontario, Canada
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Roof vents are mandatory in Ontario, i'm sure they're up there somewhere

From my code book:
Attic and roof ventilation is needed in winter to remove moisture that escapes from the building interior into the cold attic or roof space. (hot air meets cold air = moisture)

This moisture can accumulate on cold rafter or sheathing surfaces as condensation or ice and can cause potential damage. Attic ventilation is intended to remove this moisture. In summer, attic ventilation removes excess heat that can build up within the attic space.
The code says you need to ventilate 1/300 of the insulated ceiling area.

So if your house was 24'x45' = 1080 sq ft
1080 / 300 = 3.6 sq ft ventilation

Normally you would split the ventilation between the eave (your soffit) and vents at the top, so you would need 1.8 sq ft of open ventilation.

My code book is getting a good workout today, I like it

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