Thread: Ventilation Required?

Greetings all,
I'm having a hard time determining when ventilation in a roof is not required. I see builders do this a lot and I'd like to be sure when it's an issue and when it's not. IRC R806 indicates ventilation is required.
This portion of the roof (that is, the lower portion that covers the breakfast nook.) has neither soffit vents nor roof vent. Is there some condition that creates an exception to the required ventilation?

Thanks,
Michael
Scher Professional Inspections

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806.4 was added to the IRC in 2006. Unvented conditioned attic assemblies are permitted if they are constructed as specified in 806.4. The gist of it is that the insulation, air barrier, and vapor retarders must be placed on the underside of the roof deck instead of at the ceiling joists. In a space like the one in your pic, there probably will not be a way to access it once the ceilings are finished, so you won't be able to determine if it was done properly. An infrared camera could probably be used in this situation to at least determine whether the insulation is in the proper place.

In addition to what Brandon stated, if that same design was not followed in the larger attic at top, then *most likely* that design was not followed for the lower roof.

Typically (based on past experience), they installed the insulation in that area just like in the rest of the house - provided they did not forget it altogether.

Then they just 'left off' or 'forgot' the soffit ventilation for that small roof.

I've even had builders tell me: 'but that area is less than 150 sq ft, and I don't need ventilation until the area is 150 sq ft or larger, the code says so - it says 1 sq ft of ventilation for each 150 sq ft, thus that does not need any ventilation'.

My answer was always: 'No, it needs ventilation, cross ventilation, it does not require a full 1 sq ft net free vent area of ventilation is all.'

No matter what the reasoning for leaving ventilation off it is not correct. Any non vented roof is going to heat up and the shingles will burn off much quicker and by heating up it is nothing but a sucker for cooling efficiency.

I for one will write it up every time.

As far as calling for every 150 square feet requiring 1 squre foot of ventilation I don't read that just because it is under 150 square feet it doesn't need any. I see this all the time.

Ted

Originally Posted by Ted Menelly

No matter what the reasoning for leaving ventilation off it is not correct.

To the contrary, and that was what Brandon was pointing out - that there is an approved design which allows for sealed attics.

To write those up as lacking ventilation would be in error.

As far as calling for every 150 square feet requiring 1 squre foot of ventilation I don't read that just because it is under 150 square feet it doesn't need any.

Exactly what I was pointing out. That ventilation/attic space is a ratio, not a bottom limit of attic space.

All based upon the code stating (underlining is mine) "The total net free ventilating area shall not be less than 1/150 of the area of the space ventilated".

OOOOps, sorry Jerry. Another slightly misworded statement. What I should have said that if you have no idea what is under them thar shingles/roofing 'I' would write it up. Even if it is "an approved design" it still does not answer all the issues of why you should ventilate it anyway.

An attic with no roof top ventilation will kill any life expectancy of any shingle with the heat build up in the attic. The insulation in that ceiling is not going to perform as it should due to the excessive heat build up. You (him, they, me, I)could put heat reflective foil under the shingles but I do not know of shingle manufacturers that won't void the warranty.

Here I go. Am I actually going to say this to Jerry P.

Approved system or not there are multiple reasons why you would ventilate any roof/attic/enclosed space. I cannot see thru roofing material. The system is more than just likely not to be in place. I write it up as such.

I do give my reasoning to the client/whom ever for writing it up. They can do with it as they wish.

Ted

Originally Posted by Ted Menelly

What I should have said that if you have no idea what is under them thar shingles/roofing 'I' would write it up.

Depending on what is in the main attic would depend on "how" I wrote it up, but, I would "write it up" in some manner, yes.

Even if it is "an approved design" it still does not answer all the issues of why you should ventilate it anyway.

Yes it does.

Not saying that I agree with all of the answers (yet, anyway), but, yes, the answers are there.

Brandon - Thanks for the IRC 2006 contribution.
Jerry - Thank you for sharing your experience. You have a lot more than I. It's what makes this message board a valuable resource.

I have my doubts that the builder installed the insulation, air barrier, and vapor retarders to the underside of the roof deck.

I intend to write it up as 'in need of repair', understanding the risk I take. The builder may have installed the components exactly right, at which point ventilation is not required.

I wish I had a thermal imaging camera. For more reasons than one, but this would be a great application.

Regards,
Michael
Scher Professional Inspections