DIY Chatroom Home Improvement Forum

DIY Chatroom Home Improvement Forum (
-   Roofing/Siding (
-   -   Single slope roof venting (

Frederic Urich 10-10-2011 09:10 AM

Single slope roof venting
How to calculate the amount of ehaust i need for a single sloped roof that is1/12, 36'x 38', 24" overhang with full vent soffit, low end proper vents to the high end which is 3' 2" above the ceiling insulation. Looking to put a verticle wall vent at the high end that is about 2" in height for the length of the 36' wall.

AGWhitehouse 10-10-2011 10:58 AM

A very nice venilation calculator:

Gary in WA 10-11-2011 11:00 PM

That calculator wouldn't go below 3/12 for your 1/12 slope for me. The other one for ceiling attics (as in your case) would, though, the other link.

You don't mention if it has a vapor barrier on the ceiling or not. If not, figure 9 square inches for every lineal foot of soffit intake and the same for ridge exhaust vents. This gives you 1/150, 1/2 total for 1/300.

Your 2" high sounds right, depends on the screening size, spacing of the wires for the NFVA- net free venting area:

Be sure you are getting 9 NFVA at the soffits, some manufacturers of punched vinyl de-rate it correctly;

I suggest 2-3" holes to maximize the intakes and exhaust because of the very low slope.


AGWhitehouse 10-12-2011 10:59 AM

2nd link has no data...

Gary in WA 10-13-2011 09:16 PM

End of second paragraph in your link, "NFA Calculator", from here:
OP, enter your square footage and lineal footage of soffit and ridge vent........


All times are GMT -5. The time now is 09:46 AM.

vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2016 DragonByte Technologies Ltd.
User Alert System provided by Advanced User Tagging (Pro) - vBulletin Mods & Addons Copyright © 2016 DragonByte Technologies Ltd.

Search Engine Friendly URLs by vBSEO 3.6.1