Attic making apartment too hot in summer?
September 13, 2021 7:30 AM   Subscribe

I suspect the hot unventilated attic of my building is making it hard to stay cool in my rental apartment in the summer. What can I do?

I don't like to run my AC when it's perfectly nice out. Normally this works fine.

This spring I moved into a second-floor apartment. The third floor is an unventilated attic that's kept locked all the time. I can't access it (only the landlord has the key) or modify it in any way (I'm a renter).

This summer there were a lot of nice nights that got down to 70° or lower — beautiful cool summer nights. I know some places were experiencing terrible heat waves this year, and I know climate change is a thing, but the thermometer, and my skin when I stepped outside, agreed: in my town, it was getting cool enough to be comfortable more often than not.

Normally on a night like that I'd open all my windows, run some fans, and cool the whole place off. But in this apartment it just didn't work: even with tons of windows open and a great cross breeze, it stayed too hot to sleep in. Even when I gave in and used my AC, it really struggled to keep the temperature down — a lot harder than I remember it struggling in my last place.

I suspect the problem was the attic, heating up and staying hot and radiating that heat down onto me. My questions are (1) is that a reasonable theory? And (2) is there a way I can mitigate it next summer, or a reasonable (cheap, low-effort) thing I can ask my landlord to do that would mitigate it?
posted by nebulawindphone to Home & Garden (11 answers total)
Short of your landlord venting the attic, I don't think there's much you can do other than to buy one or two large, high velocity window fans like this one to exchange the air inside your apartment as rapidly as possible on those days when it's cooler outside.
posted by RonButNotStupid at 7:44 AM on September 13

Response by poster: (Oh, um, I misspoke a little: by "unventilated" I actually mean "windowless." I have no idea if there's some other kind of vent.)
posted by nebulawindphone at 7:47 AM on September 13

The attic is probably the problem, and yeah I'm not sure there's much to be done beyond properly insulating and venting the attic. I had a similar experience in a previous apartment - the first summer I had some Lush lotion bars that literally melted into a puddle on a hot day. Then that following winter the house got ice dams and major ceiling leaks, which led the landlord to get the attic dealt with. My apartment was completely comfortable the following summer (AND my heat bill went down the following winter). So my advice to you is to try to encourage ice dams this winter? Or maybe try to encourage your landlord to get an energy audit for the building.
posted by mskyle at 8:15 AM on September 13 [1 favorite]

I would try touching the ceiling on one of those cool outside hot inside nights and see if it's warmer than the walls.

It would be strange to have an unvented attic unless the attic is insulated up the roof rafters.

More insulation would almost certainly help.
posted by gregr at 8:51 AM on September 13 [1 favorite]

More insulation would help, but I would doubt your attic is heating your home up at night. The heat up there will be stored heat, and unless you attic is made of heavy stone, stored heat would burn off very quickly on a cooler night. If it didn't burn off, then the attic would be very well insulated, wouldn't it?

In the day time, yes for sure. But at night? I doubt it.
posted by The_Vegetables at 9:17 AM on September 13

I would try touching the ceiling on one of those cool outside hot inside nights and see if it's warmer than the walls.

Much easier and more accurate: get one of those non-contact thermometers (such as this one) and take readings of your ceiling (and walls, for comparison) at several spots.
posted by Stoneshop at 9:20 AM on September 13 [2 favorites]

My guesses would be the cross-breezes you are trying to create aren't working very well, the humidity is high, or night temperature cools later than you might guess, and doesn't stay cool that long.
posted by The_Vegetables at 9:20 AM on September 13

My apartment is in an old building and traps heat in the summer. I can have all the windows open and fans running on a beautiful cool summer night and still be sweaty and uncomfortable. Not all units are created equally in this regard. It's frustrating!
posted by cakelite at 9:46 AM on September 13 [1 favorite]

It is a bit odd to have heat radiating down unless the attic is incredibly hot and is warming/heat-soaking your ceiling, a lot.

I'd be more inclined to find out about the apartment below you and whether or not that is where the heat is originating. It is possible that the apartment below you is using heat—even with their windows open—to keep the chill off but are cooking you out. If the units have high ceilings, it might not feel hot to the occupants but certainly to you.
posted by bz at 12:07 PM on September 13

I agree that it is possible that convective heat may be rising from your neighbors below, but infrared heat transfer (sometimes called radiation) from a hot attic to objects below also happens and that radiation is omnidirectional. The way to stop it is to block and/or absorb it. A radiant barrier in the attic above your ceiling would do it, but if your landlord has not done this yet it's hard to imagine them doing it now (it certainly does not hurt to bring it up). As a renter I'm not sure you have many options that aren't ugly or permanent. Radiant barrier is not aesthetically pleasing unfortunately.

Blowing hot air out of the attic doesn't change the way radiant heat moves into your living space, so ventilating the attic won't really help. It may actually cause more cooling loss from your air conditioned space upward (through convection), if your space is not well sealed.

I wish I knew a solution- we have a small cabin in a place that regularly hits 100 over the summer. There's no attic- the underside of the roof is our ceiling. Even with the AC cranked you can put your hand up and feel the radiant heat from above.
posted by oneirodynia at 3:59 PM on September 13 [1 favorite]

I wish I knew a solution- we have a small cabin in a place that regularly hits 100 over the summer. There's no attic- the underside of the roof is our ceiling. Even with the AC cranked you can put your hand up and feel the radiant heat from above.

The solution for that (again, for during the day), is to put 1-2" radiant barrier panels under the roof decking next time you reroof, or to put spray foam insulation in the 4" space for the lumber holding up the roof, and then drywall over that.

Solutions are unfortunately weather-specific, and hot places should not have cathedral ceilings without any space for insulation. Those are only for temperate places.

However, we are talking about the night with the OP. I'd bet your cathedral ceiling bleeds heat quickly at night. So if you felt your ceiling at midnight and the outside temperature was 65F, then it's going to be cool, not radiating heat.

Also insulation or radiant barrier or whatever will still only cool a room to around the ambient temperature minus any cooling via airflow or forced air conditioning, so if it's 100F and the attic in the place is not cooled, then close to 100F is going to be your baseline.
posted by The_Vegetables at 8:14 AM on September 14

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