Thread: Soffit ventilation

Hello, I performed a new construction inspection today and observed that there was no soffit vents along the back of the house (hip roof). Is it true to say that there should be soffit ventilation around the perimeter of the house?

Thanks

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Not necessarily required to be on all sides.

They have to meet the requirements outlined in IRC R806, including total net free ventilation. It's possible to meet the required 1/150 (or 1/300) NFA by using intake vents on several sides as long as it is balanced upper to lower.

If the math for that attic works out to 10 sf of NFA (for example), they can split that for 5 intake and 5 exhaust.

Dom.

Michael,

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Originally Posted by Michael Vasquez

Is it true to say that there should be soffit ventilation around the perimeter of the house?

Originally Posted by Dom D'Agostino

Not necessarily required to be on all sides.

Depends. (I know, that is you said Dom said "Not necessarily". Just explaining it further.)

From the 2006 IRC. (underlining is mine)

- R806.1 Ventilation required. Enclosed attics and enclosed rafter spaces formed where ceilings are applied directly to the underside of roof rafters shall have cross ventilation for each separate space by ventilating openings protected against the entrance of rain or snow. Ventilating openings shall be provided with corrosion-resistant wire mesh, with 1/8 inch (3.2 mm) minimum to 1/4 inch (6 mm) maximum openings.

Originally Posted by Jerry Peck

Just explaining it further.

Thanks Jerry, I didn't have the text handy to paste into the reply.

Dom.

try this http://www.airvent.com/pdf/literature/PAVbooklet.pdf

I would think that some roofing manufactures might have a problem with not venting all sides.

Originally Posted by bruce m graham III

try this http://www.airvent.com/pdf/literature/PAVbooklet.pdf

I would think that some roofing manufactures might have a problem with not venting all sides.

Bruce,

"might have a problem with not venting all sides"

I don't see anything about that in there.

They are referring to a "Balanced System", i.e., "balanced" between high vents and low vents.

The only thing requiring "cross ventilation" is in the code. Thus, if you have a hip roof and 2 sides are vented at the soffits, you have "cross ventilation".

Now consider having 3 sides with soffit vents - is that "cross ventilation"?

Maybe.

It definitely is for the two opposite sides, and those two opposite side would allow for some cross ventilation to the other side. Does it then need soffit vents on the opposite side from the third side? In my opinion, yes, at least some - but is it "required by code"?

Maybe. I would say yes and let the AHJ overrule me.

More importantly than that, how many HIs do a rough calculation on the total attic size (including overhang) and the amount of venting provided versus the amount of venting required?

Those who do I would suspect find many instances where the ventilation is nowhere near close to what is required.

Jerry,
You are quoting out of context. my statement was not related to the pdf but a general observation on my part.
and yes I do find alot of homes that lack proper ventalation.

Originally Posted by bruce m graham III

Jerry,
You are quoting out of context. my statement was not related to the pdf but a general observation on my part.

Bruce,

My mistake, then.

You stated, as a general observation, "I would think that some roofing manufactures might have a problem with not venting all sides.", in which case I would agree ... roofing manufacturers will find whatever reasons they can for dis-allowing a warranty claim, and improper ventilation would do it, as would inadequate ventilation (which is not necessarily the same as 'improper ventilation' - one could have 'inadequate' 'proper' ventilation.).

agreed

Not venting the soffit on one side seems like a poor practice to me. I can't tell you how many times I have seen mold/ mildew growth between rafter bays that lack eave vents, while bays with eave vents are good as new. It seems like you will not have good air flow along the entire lower non ventilated section, which could end up leading to problems.

Originally Posted by Brandon Whitmore

Not venting the soffit on one side seems like a poor practice to me. I can't tell you how many times I have seen mold/ mildew growth between rafter bays that lack eave vents, while bays with eave vents are good as new. It seems like you will not have good air flow along the entire lower non ventilated section, which could end up leading to problems.

To do it that way would require "continuous" vented soffit, it would not allow for anything else (unless one were to install a vent *at each* rafter/truss area).

I think you are seeing some other cause/problem, not one related to 'poor venting'.

Check out these "Continuous Soffit Vents" here... I've just installed them in my house and the installation went off with no problems, they look great, and supply more than enough ventilation between the ridge venting and the soffit venting. Wood Soffit Vents-Whitehaven Wood Products-Continuous Soffit Vents, Handcrafted in Canada

Is there any way to post a picture here, or not?