I am looked at a home that has no attic ventilation, no ridge vents, no off ridge vents, no soffit venting and no attic fan. The home has sprayed foam insulation on the trusses and sheathing. It has 2 air handlers in the attic. The home owner is telling us that with the spray foam it does not need ventilation. I am not so sure on this one. A little insight please.
I’m curious where you are located, but in my life’s experiences, an attic without ventilation was an attic with problems. Even a tiny roof leak will destroy the decking in an unvented attic (one of my pet peeves with manufactured housing). You mentioned air handlers in the attic- a common practice in Florida, I know, at least. A condensate drain clogs, and then what? Water vapor migrates through from the living space- and goes where? I’m interested if there is some new practice in play here, but otherwise I say go with your gut, and stick to your guns. To me it sounds like a really bad idea.
This subject has come up several times. Depending on several factors, lack of ventilation can be an issue. ICC finally caught up with it in the 2018(?) cycle. Florida Building Code in 2020 edition. I bumped one of the previous threads…
https://forum.nachi.org/t/spray-foam-attic/153906/16
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I was going to say this subject has come up many times recently. In nearly all the threads it turned out there were hvac registers in the sealed attic making it just another conditioned space. Is that the case here? The merits and concerns of spray foam on roof sheathing is a separate issue.
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As mentioned, it should be conditioned.
Here’s a good article on the subject of unvented conditioned attics.
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Closed cell foam or open cell foam? Hopefully the former. Like said, search this forum for past discussions.
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A non-vented attic system uses an air seal to create a “conditioned attic.” The building envelope has been moved to the roof deck. No ventilation warranted.
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As long as there is an HVAC supply and return, it’s completely fine . It is considered conditioned space. Not a problem at all
You are wrong. As long as it has a HVAC supply and return, it is completely fine.
I have found no provision in GA that it needs to be conditioned. Similar to a basement, it is apparently considered a passive space.
Some basements perform well without conditioned air; some do not. In my experience, it’s the same as the SPF attic. If it were my home, I would condition the space.
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Got it. I tripped on the terminology; in my mind I equated “unvented” with “no ventilation”. I read the attached info and saw my error- it’s literally “lacking vents”, not “lacking ventilation”, with ventilation meaning a provision for exchange air or other way to remove any incident moisture. I really just wanted to tag the thread to come back later and see what those of you more experienced than I had to say. I should have said less, like maybe “.”, maybe. lol
Go figure. 
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As noted by others above, it is now inside the thermal envelope and considered “indoor” space. Treat it as such by running supply and return air ducts. The other thing I mention to clients in this situation is that they should pay particular attention to keeping their roof covering in good condition.
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When properly foamed/performed no attic ventilation to the exterior is required. However you appear to be located in Climate Zone 1 which might require conditioning from the HVAC unit. Only you know the conditions to determine this. You can refer to IRC R806.5 for the conditions that would require this.
Keep in mind that Building Codes do not dictate good building practices. In fact it is opposite that good building practices dictate what is in the Building Codes. So even though an Inspector is not “inspecting to the codes” they are a guide for what is right and wrong.
One question I do not see asked here are how are the two furnaces obtaining their combustion air?
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Not all foamed attics will require a conditioned air supply. However even if they do not I do recommend them anyhow to help prevent possible large temperature differentials on either side of the ceiling gypsum board. That can contribute to possible issues in all seasons. Not only that the cost of adding it is so minimal compared to the potential benefits. Alas Builders will go cheap and retrofit insulators won’t quote it so they don’t lose the job to another.
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GA is Climate Zone 2 and IRC R806.5 can be used as a guide.
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@Emmanuel_Scanlan ,
Air handlers, not furnaces- so just A/C evaporator and blower motor, typically with an optional electric heat strip for those 2-3 cool nights per year.
You’re going to have problems. Moisture will find a way and when it does the humidity in that space, especially with the air handlers will rise above normal. Sometimes a dehumidifier is needed or alternative duct your A/C system into that space. So if they put in a supply vent, in theory at least it should also have a return vent…
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Correct, and the GA IRC with amendments has deleted section 5.2 which covers conditioning the space.
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if the attic insulation is on the roof structure and you add ventilation, you no longer have an insulated attic. Your attic conditions will be heavily affected by the weather at the time.
Think about the following pictures. They insulated the roof decking and did not block the soffit vents. New construction.
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