# Round soffit vents worth effort?



## roofermann (Nov 18, 2013)

Adding soffit vents can't hurt. Use a hole saw in a drill for the holes. Block the gable vents, as they will prevent the ridge vent from drawing air from the soffit.


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## marriedmanw (Feb 28, 2010)

roofermann said:


> Adding soffit vents can't hurt. Use a hole saw in a drill for the holes. Block the gable vents, as they will prevent the ridge vent from drawing air from the soffit.


Thanks Roofermann for the suggestion. I know I need to get more ventilation going to attic since it's now 81F outside and attic is 111F.


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## Gary in WA (Mar 11, 2009)

Figure a 18" sq. NFVA ridge vent is divided by both sides of a gabled roof; OR 9"sq. NFVA* per lin. foot* of soffit to exceed the (1/300) Code down to 1/150; http://publicecodes.cyberregs.com/icod/irc/2009/icod_irc_2009_8_par091.htm

If 172' of soffit (?), you really need to vent every rafter bay (if 24" wide) with 2- 6"new to beat code minimum and help control temps/moisture. Check my math and yours; http://www.airvent.com/homeowner/products/intakeSoffit-specs.shtml I'd think you may need to remove the vinyl and add continuous venting, pp. 615-617 here; http://books.google.com/books?id=Z8...page&q=attic airflow with gable vents&f=false

Gary


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## Mike in Arkansas (Dec 29, 2008)

Just finished installing 8 x 16 vents around my soffit on a two story house. I can say unequivocally that a recipicating saw works a lot better and a lot faster than a jig saw. I started with a jig saw then left to buy a course wood blade for my cheap recipicating saw.


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## Gary in WA (Mar 11, 2009)

To anyone adding venting at the soffits; keep in mind you are trying to reduce moisture/heat gain/ice dams with ventilation. Optimum is *washing every single rafter bay *with inlet ventilation supply around the perimeter of heated area (moisture is not picky when condensing on roof sheathing/framing). Location/size/louvers/screen of the vents are also very important at the soffits;last link stated above... Spacing the venting out with 8x16's (65 NFVA) is less than optimum at *7' apart* for 1/150, or *14' apart *for 1/300 venting though much easier to do than continuous venting; http://www.lomanco.com/vents/intake-vents#!prettyPhoto
especially when relying on passive/wind pressure venting (non-powered). You couldn't help but have a lot of unvented roof sheathing surface areas. Unless wind-driven, the supply air splits; some up the sheathing following the pitch (due to thermal buoyancy), some across the ceiling plane over the insulation (through the top inches if fiberglass - lowering R-value, unless covered by a housewrap) and eventually exiting the ridge after convective looping first, taking some of your money (heat) with it- 24/7. Be sure to air seal the attic first- more important than ventilation or insulation.

Gary


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