Single slope roof venting

Frederic Urich · 10-10-2011, 10:10 AM

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, 11:58 AM

A very nice venilation calculator: http://www.metalera.com/CalcAboveSheathing.aspx?id=2094

**Gary in WA** · 10-12-2011, 12:00 AM

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: http://www.airvent.com/homeowner/pro...it-specs.shtml

Be sure you are getting 9 NFVA at the soffits, some manufacturers of punched vinyl de-rate it correctly; http://files.buildsite.com/dbderived...rived92755.pdf

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

Gary

AGWhitehouse · 10-12-2011, 11:59 AM

2nd link has no data...

**Gary in WA** · 10-13-2011, 10:16 PM

End of second paragraph in your link, "NFA Calculator", from here: http://www.metalera.com/CalcAboveSheathing.aspx?id=2094
OP, enter your square footage and lineal footage of soffit and ridge vent........

Gary

10-10-2011, 10:10 AM	#1
Frederic Urich Newbie Join Date: Oct 2011 Posts: 1	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. Last edited by Frederic Urich; 10-10-2011 at 10:22 AM. Reason: confusing

10-10-2011, 11:58 AM	#2
AGWhitehouse Architectural Designer Join Date: Jul 2011 Location: Connecticut Posts: 1,370	Single slope roof venting A very nice venilation calculator: http://www.metalera.com/CalcAboveSheathing.aspx?id=2094 __________________ Life's too short...so enjoy it! To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

10-12-2011, 12:00 AM	#3
Gary in WA Moderator Join Date: Mar 2009 Posts: 8,843	Single slope roof venting 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: http://www.airvent.com/homeowner/pro...it-specs.shtml Be sure you are getting 9 NFVA at the soffits, some manufacturers of punched vinyl de-rate it correctly; http://files.buildsite.com/dbderived...rived92755.pdf I suggest 2-3" holes to maximize the intakes and exhaust because of the very low slope. Gary __________________ Clothes taking longer to dry? Clean the dryer screen in HOT water if using fabric softener sheets. They leave a residue that impedes air-flow, costing you money. Clean the ducting in the last six months? 17,000 dryer fires annually!

10-12-2011, 11:59 AM	#4
AGWhitehouse Architectural Designer Join Date: Jul 2011 Location: Connecticut Posts: 1,370	Single slope roof venting 2nd link has no data... __________________ Life's too short...so enjoy it! To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

10-13-2011, 10:16 PM	#5
Gary in WA Moderator Join Date: Mar 2009 Posts: 8,843	Single slope roof venting End of second paragraph in your link, "NFA Calculator", from here: http://www.metalera.com/CalcAboveSheathing.aspx?id=2094 OP, enter your square footage and lineal footage of soffit and ridge vent........ Gary __________________ Clothes taking longer to dry? Clean the dryer screen in HOT water if using fabric softener sheets. They leave a residue that impedes air-flow, costing you money. Clean the ducting in the last six months? 17,000 dryer fires annually!

Single slope roof venting