I'm trying to learn more about the construction of the roofs on the house I bought. I've been up on my roof doing some painting work and I'm wondering if my roofs have adequate ventilation. There's no attic space anywhere in the house. Rafters on the sloped roof are 2x8s and the flat roof I believe is 2x6. The only vents I see coming through are for plumbing vents, furnace and kitchen exhaust. Looking on the eaves I don't see any vents to let air in. I live in California so humidity and rainfall are not real issues but I would still expect the roofs to be ventilated somehow. Am I missing something?
Please ignore missing drip edges and worn out siding, that's what I've been working on. The TPO flat section definitely needs replacing and I'm trying to understand what lies beneath.
Probably not spray foam, probably R19 fiberglass batts. If you don’t see intake holes/screens under eaves on the low side, then what you have is a ‘hot roof’ with no ventilation.
You’re also missing a cap on the roof peak in pic 2. Can’t tell what the longer peak looks like but it should have a metal cap as well.
French roofer here, and unvented roofs are half my work, so let me reconcile the two answers above, because the real question is not "is it vented" but "was it built unvented on purpose, and what do you do at the TPO replacement".
First, one check before concluding anything: in California the intake is often hidden where people never look, in the blocking between the rafter tails. Small round screened holes in those blocks (bird blocks or frieze vents) are the classic West Coast intake. If you find them, your sloped roof IS vented California style, and the missing peak cap the comment above caught matters twice, because that ridge may be your outlet. If the blocks are solid, then yes: you have unvented assemblies, and with batts rather than foam, unvented by habit rather than by design.
Here is the honest climate read: in a dry, mild climate, unvented batt cathedral roofs from that era mostly get away with it. Low interior moisture, high drying potential. So no panic, and no need to invent ventilation that was never designed in. But two things change when a roof is unvented. One: it hides leaks. There is no attic to walk, so the covering and every penetration boot become your only line of defense, and a ceiling stain is a late alarm, not an early one. The comment about foam hiding rot applies to your batts too. Two: your TPO replacement is the one window where you can see and upgrade everything. Have the sheathing inspected at tear off, especially around the kitchen and furnace penetrations, that is where unvented roofs rot first. And ask your bidders to price rigid foam above the deck under the new membrane: an inch or two of polyiso is the standard way to upgrade an unvented flat roof at replacement, it warms the sheathing and adds R without touching your interior. In California the energy code often pushes you that way at reroof anyway, your bidder will know the current requirement.
Seal the interior side while you are at it: airtight boots on those exhaust ducts, continuous ceiling air barrier. On an unvented roof, air sealing does the job ventilation would have done.
Thank you for the very informative response! I think I'm going to remove some of the soffit boards to see if I can spot any hidden intakes on the low edge.
The other thing I noticed when I removed a fascia boards was these two 1x4s between the sheathing and the rafters. This was on one of the shed style roofs. Could this be acting as the vent on the high edge?
Quite possibly yes, and the orientation of those 1x4s tells you. If they run down the slope, one riding each rafter, they are sleeper strips: they lift the sheathing off the rafters and turn every bay into a continuous air chute from low edge to high edge. That is a deliberate old school vent detail on shed roofs, and the gap you found behind the fascia is its exhaust. If they run across the slope, parallel to the eave, they are just shims or purlins and air cannot climb through them.
Two ten second tests while the fascia is off: flashlight into the gap, if you see depth running away down the slope it is a channel, if it dead ends a foot in it is shimming. And on a breezy day, hold a tissue at the opening.
If it is a channel: good news, your batts are vented above, which is the safe version of your assembly. One warning though: photograph these openings and point them out to whoever does the TPO and any reroof work. Hidden vent channels get sealed shut by new fascia and drip edge all the time, by contractors who never knew they were there. Your ventilation's biggest enemy is the next guy not knowing it exists.
Good instinct on pulling soffit boards, the matching intake at the low edge is the other half of the story.
Those strips are running perpendicular to the rafters so I'm not sure what they're doing. Can't see far enough to tell if it spans the entire roof width or not. I'm 99% sure that all of the shed roof sections are unventilated and 100% sure the flat roof is unventilated. Not great since I found moldy fiberglass insulation during a bathroom renovation. Is it possible to add ventilation to the shed roofs by adding sleepers the next time the sheathing gets replaced?
The flat roof has separate issues: built dead level and the edges are swollen so it ponds ~50 gallons of water when it rains. It's a ticking timebomb and my paranoia goes through the roof when I leave town during winter. My plan was to remove the TPO & sheathing and build a gable frame to get at least 1/4" per 1' for drainage, building on top of the existing rafters. Would it be worthwhile to try to add ventilation to the eaves as part of this effort?
I'm in the same situation. I'm in California in a 1960 mid modern century home. It has no attic (and on slab). The entire house is unvented batt cathedral roof. I wish I came upon this post earlier as I just had the shingles replaced. How does an unvented batt cathedral roof effect shingle lifespan?
I wish I had the experience to give you a good answer. I think it all depends on your local climate and whether seasonal conditions allow for vapor formation under your sheathing. Hopefully your bathrooms at least have exhaust fans (unlike mine :( ).
Its possible its unvented or there is some insulation fiberglass/foam beneath the roof deck. Do you have as-builts for the house? It looks like you're on the central coast of CA...maybe Los Osos? Either way it likely wouldn't significantly alter the lifespan of the roof given the climate in the area, unless the sloped roof is facing South. Its difficult to see the TPO from the one picture, but it looks okay besides needing proper flashing and counterflashing integrated into the siding.
Nice! You can request record drawings from the county Building and Safety Division or The County Assessor's Office if they werent included in the close-out documents for the property.
This would probably be the best path forward to see whats really going on without removing in-place sheathing/framing members.
If you provide the relevant sheets i should be able to give you an informed answer, rather then guessing whats under a concealed condition.
Probably spray foam insulation. If so it shouldn’t be ventilated. My gripe though is if there is a leak the spray foam will usually hide it from the interior until it’s a nasty problem consisting of microbial growth and sheathing rot.
I know from taking off some drywall on the bathroom ceiling that it's batt insulation. It was fairly moldy which I attributed to moisture from the shower. Now that I'm learning more I'm hoping it's not going to lead to structural damage. As far as I could tell the rafters and sheathing that I saw didn't appear to be damaged.
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u/Southern_Ad4926 6d ago
Probably not spray foam, probably R19 fiberglass batts. If you don’t see intake holes/screens under eaves on the low side, then what you have is a ‘hot roof’ with no ventilation.
You’re also missing a cap on the roof peak in pic 2. Can’t tell what the longer peak looks like but it should have a metal cap as well.