Well, wall insulation requirements are much less than ceiling, right? Not so much so that the wood suffices, but still.
Also, yes, sometimes the tops of ceiling joists are visible in attics with blown-in insulation… but that is usually a first sign of inadequate insulation, in my experience.
edit: I’m just spinning my wheels for the heck of it, I provided information & observations to my client and deferred judgment to an expert. its all good.
So this has always been my position. However, recently I went down that rabbit hole in GA and found no such requirement.
Is this a cold weather requirement? Also, and I’m hoping someone will help with the research. Does spray foam applied to roof decking have a lower R-value requirement than ceiling insulation?
As a Building Analyst (energy audit) the exposed rafters are included in calculating the actual R value of the ceiling/roof. Same for a wall system. It’s not a defect. It’s a commonly used building system.
As a home inspector, it’s not a defect. It’s how the home was built, simply that. Not all homes are built to be super insulated. You may be opening a can of worms by calling this a defect, vs reporting it as “as built”.
New construction, both surfaces require the same; R-50 in MN when energy heel is present. Otherwise, R-60 wherever possible. When the roof deck is insulated, the attic is conditioned space. The gable has to be insulated too. No direct heat source required in a conditioned and unoccupied attic (scuttle access).
So what satisfies the conditioned space requirement if there is no direct heat source?
What does the use look like? I would consider calling need for heat if there was a permanent stair with sufficient floor structure to support 40psi LL and 10psi DL. I’d definitely call it if there was a room up there. I wouldn’t call it if it was just storage. It’s a judgement or opinion call…
But isn’t one of the reasons to condition that space to prevent excessive moisture build-up entering through the ceiling surfaces below?
I’m in zone 6 which is a little warmer than Mike in zone 7 and I like my R-28 foam side walls and R-60 cellulose attic ranch on a basement w/R-15 rigid side walls and cracks & holes foamed or caulked. My 54,000 btu nat gas furnace does a great job on 2,450 sq. ft.
Carry on…
I’m trying to understand more about what actually happens in this space. The attic is sealed so technically there should be no significant stack effect. Also, depending on climate zone, a vapor barrier or retarder is recommended prior to spraying. (I think closed cell foam is sometimes used). Code seems to be mostly silent on this.
The dew point will not be on the foam insulation face. In severe cold, there may be a condensation issue on the exposed framing, or maybe not. Closed cell foam is critical IMO and does not require a vapor barrier. Open cell spray foam is a second issue of concern, if present. From my knowledge and maybe experience, if there is enough moisture in the home to cause condensation on the rafters, the same issue will be more severe on the windows inside the home. Then you have an indoor air quality issue, requiring a HRV.
Brian: Vapor barrier on the conditioned side of the insulation, at least in my climate zone. AC, another issue.
So the attic space is not part of the thermal envelope?
If that’s the case I imagine closed cell would need to be installed between the rafters and closed cell and or a moisture barrier would have to be installed over the ceiling, and just pray nothing ever leaks from above or below.?. 
Here’s a good article on the issue.
So aside from any potential moisture issues, I wonder which is more efficient, encapsulated that’s conditioned, or encapsulated thats not contioned.
Personally I think I would opt for conditioned.
Thanks for the input Michael!
For what it’s worth, it is not common in Texas. I can usually only see collar ties.
Attics should be thought of just like crawlspaces. Either treat them as the outdoors, or treat them as the indoors. Most attics in my area are treated as the outdoors (vented by soffit, ridge, gable, etc.).
If the attic is closed off/insulated to the outdoors, it should be treated as indoors with a supply and return of conditioned air. Otherwise the stale, humid air that is trapped in there will eventually cause problems.
I’ve only seen a conditioned spray foamed attic once in Texas, and it was a particularly high end home, that also had a fire sprinkler system, to give you an idea of the sort of home it was.
Sometimes I see a mechanical exhaust fan in spray foam attics.
I’m not disagreeing. I haven’t found the requirement such as with crawlspaces which is pretty clear.
That’s one way to vent it to the indoors. I would prefer to see a supply and return duct myself. It can be dampened down to fit the space and the desired airflow.
Can’t say I know if it is a requirement I guess. Just one of those common sense things. Can you imagine cracking open a sealed attic that had no means of ventilation after 20 years? My guess is it would be pretty ugly. It’s kinda like how closets with tight fitting doors that never get opened tend to get musty and even moldy in some cases.
I agree with Ryan, the space is either inside of the theramal envelope or it’s not.
Although different climates may have different circumstances, to me it seems if at a minimum you don’t circulate and move air you’ll end up with moisture issues.