Help me beat the heat (in my attic)!
July 3, 2012 2:02 PM   Subscribe

Calling all home improvement gurus and energy efficiency wizards--help me figure out how to better insulate my attic! I've read through a bunch of information on and other websites about insulating attics, but the more I read the more confused I get about how to do this, because I have the world's weirdest attic. HELP.

So, we recently purchased a lovely small brick house in Colorado with no A/C. For the past few weeks, I've been dying of heat inside nearly every day--which was quite surprising, as the rental I used to live in down the street (same size, but made out of river stone rather than brick) had no A/C but remained a lovely 70 to 75 degrees no matter how hot it was outside. I suspect the issue is heat leaking down from that attic, and I'm desperate to fix it.

The primary air leak appears to be through an enormous and not-well-sealed set of attic stairs. The stairs were built by a previous owner, and use a rope-pulley system to allow someone to basically pull down 10 feet (yes, you read that right) of the house ceiling/attic floor into the main space of the house. The pulley system plus the size of the hole in the ceiling for the damn stairs (3 feet wide by 10 feet long!) means it's not going to be possible to just add on an attic tent or build a box to seal off the air flow, which was my original plan. So, I'm thinking we need to add insulation to keep the attic itself cooler, because then at least the air leaking into the house wouldn't be SO DAMN HOT.

However, all the information I'm able to find online about adding insulation assumes that the CURRENT insulation is tucked in along the floor joists of the attic, and suggests just laying more on top. (Oh, how I wish it was that easy!) In our house, the joists are actually covered by wood making a flat, regular-looking floor, and the R-19 insulation is tucked up along the attic ceiling between the rafters and along the attic walls. Not around the whole attic, mind you, just in a 20 foot by 10 foot area centered around the attic stairs. So, my questions are:

1. Am I right in thinking that the best way to accomplish my ends is to insulate along the attic ceiling rather than along the attic floor, given that it doesn't appear we can totally stop the air flow from the attic space into the house? Or would there be some benefit to spreading insulated batting all over the floor, except for the gaping 30 square foot hole that is the attic stairs?

2. How in the world do we add more insulation to the attic ceiling, when it doesn't look like there is any room to tuck more insulation between the rafters? (The rafters aren't that deep.) Should we rip out the R-19 that is in there and replace it with something bigger?

3. Is the current set-up of an "insulated room constructed from R-19 batting inside the attic" (that is, insulation doesn't run all the way to the outside edges of the attic) going to cause us problems in the winter, or is it okay assuming the only real air leakage we have (that I know of) is inside that little insulated room?

4. One idea I had was to install radiant barrier loosely hanging off the rafters, which should at least cut down some on the heat radiating down from the asphalt shingle roof into the attic (and subsequently from the attic into the house). I think this should help with the heat in the summer, but probably won't do anything to help heat from leaking out into the attic in the winter. Is there a better solution, or is this the best I can do?

Sorry for the long question--there's a ton of great information about insulating attics on the internet, but none of it appears to address the total weird factors in play in my attic. I'm hoping some mefite with more handyman/DIY experience might have some good ideas for me.
posted by iminurmefi to Home & Garden (12 answers total) 5 users marked this as a favorite
I think more insulation may not be your best option- while you may delay the transfer of that heat, the prolonged heat of summer will eventually overcome any amount of additional insulation that you may be able to install. You may be better off researching your options for ventilating your attic- something on the order of a ridge vent or attic fan. Here's some info.
posted by EKStickland at 2:21 PM on July 3, 2012

making some assumptions here but the hole for the stairs is kind of a red herring. the reason why your house is so hot is because your attic isn't properly insulated. as a bonus, in the winter your house is going to be really cold unless your house is in the hidden tropical part of colorado.

just one point ahead of time. the max R-value of fiber glass insulation is determined by the depth of the joists/rafters it's fitting in between, so you can't just added higher R-value batting.

in general, it would be better to insulate the attic floor than the roof itself (better for the roof). actually the attic floor might be insulated (check this), but assuming that this isn't so and is otherwise impractical you NEED to insulate that roof.

here is what i would do:

1) put in R19 batting in the rest of the roof. are the walls in the attic the same thickness as the roof? if not put in the approriate R-value batting in the walls.

2) (optional) attach the thickest silver-backed rigid foam panels you can afford over the batting and tape the cracks of the panels with tyvek tape (heat/cold resistant tape). this will increase the R-value of the roof, insulate thermal transmission through the rafters and provide a radiant heat barrier.

3) if you don't choose to do (2) put up vapor barrier over the batting.

4) go through the house and stuff in loose fiberglass insulation into all of the electrical sockets and wall/ceiling fixtures or purchase foam inserts for the fixtures. this keeps air from getting sucked into the walls and up into the roof where moisture can accumlate.

all of this is a significant project and will cost some money. however you can get tax credits/deductions as energy efficiency improvements... good luck.
posted by at 2:32 PM on July 3, 2012 [1 favorite]

Ventilation is step one, yes. You need to do that even if you are insulating, because otherwise you'll end up with a moisture problem and then a mold problem.

The reason all the information is for insulation on the attic floor is because that's where unfinished attic insulation goes. However, in your case you have a sort of semi-finished attic. You have to decide where you want you "heat envelope" to stop. If you want to continue using the floored attic as a storage space that you heat and cool along with the rest of the house then you're going to have to insulate the rest of the slopes and kneewalls. If you don't care to keep the attic as a conditioned space, then rip out the old patchy fiberglass, rip up the floors and insulate per the books. You can solve the air leakage problem around the access by just stapling some Q-Lon around the edge and making sure it seals properly when closed (note: this will pointless unless you're insulating the attic floor).

Not to step on anyone's DIY spirit, of course, but it may be worth checking with you Electric or Gas company to see if they're running any insulation programs. What I know of insulating came from working many summers for my dad's insulation company, and right now they're inundated with people referred to them by the Utility Companies. Several in the Northeast right now are offering to pay up to 75% of the costs to have insulation professionally installed (these programs are NOT income bound. The programs that are are 100% subsidized.) Usually that comes out cheaper than buying the materials at Home Depot.
posted by Freon at 2:44 PM on July 3, 2012 [2 favorites]

For sure you want to insulate the rest of the roof. Get whatever R-value of insulation fits your roof joists and spend a hot, sweaty weekend stapling it in place.

Look into blown-in insulation for the attic floor. If your attic floorboards have a lot of gaps, you might be able to get it in without pulling anything up. If they don't, you could still get it in while only pulling up a sampling of them. Big-box hardware stores sell/rent the stuff to do this, it's easy enough.

Think about laying some thick blankets and/or tarps over the attic stairs or building some kind of overhanging gasket or baffle to reduce air flow there.

If your attic isn't actively ventilated, you should install a fan (you can get nice thermoregulated ones) to help get hot air out of there when it heats up. This may be doable as a DIY project if you have a window/vent in the eaves, otherwise if you have to cut a hole in the roof then I'd call in a pro.

If your attic is the cause of your heating woes (which it sounds like may well be the case) then doing all that oughta fix it for ya. If not then you'll need to look into other issues. You might want to see if you've got decent insulation in your walls or not, and look into improving ventilation throughout the living area. You could also plant some large bushes, or shade trees, or some clumping bamboo or something on the south side of the house to help keep the sun off the building. That would take a while to grow in, but it'd help in the long run.
posted by Scientist at 2:48 PM on July 3, 2012

Oh, and yes! Freon's suggestion that you look into subsidies is excellent, you might be able to get an amazing deal here and get this done for cheap.
posted by Scientist at 2:50 PM on July 3, 2012

Oh yeah, if you can rent a cellulose blower that makes the attic floor insulating much easier. Be sure to install baffles so you don't block the soffits, otherwise you'll never low ventilation. The accepted trick in this situation is to just drill holes in the floor the width of your nozzle and fill the bays without having to rip up the boards. Then blow OVER the floor so that the combined depth of the bay and the cellulose on top comes to about 13.5" for R-49.

Just remember, it's attic floor OR slope and kneewall, not both. If you do both you'll end up with an expensive waste, a moist mess, or both. Insulation is like a perimeter, or envelope. You should be able to visualize your insulation around your home like a candy coating with no spaces in between. Walls, attic, and floor insulation overhead in the basement if your basement is unconditioned. If you do attic floor AND slope you'll have this weird gap of dead air in between. Mold loves that gap.
posted by Freon at 3:00 PM on July 3, 2012 [1 favorite]

What freon said about the heat envelope is the number one thing you need to decide. Heated attic or cold attic? Totally different animals.
posted by fshgrl at 3:01 PM on July 3, 2012

The best bet might be to get a new roof using white/light color metal or white shingles that are built to be reflective. The next thing to do is the rigid foam panels as thick as you can find like outlines.

If it is a samll house with a simple roof layout than the new roof might be the best payoff. You can get a 20-30 deg drop in attic tempatures from this alone and no matter how good your insulation is it will eventually heat up enough to leak through. Better to stop the heat in the first place than insulate to even out day/night fluctuations. If you do get a new roof, pay attention to venting the space to create a wind catcher effect if you can with louvre/soffict and gable vents and a ridge vent on every roof ridge you have. This can drop tempatures a significant amount on top of the gain(loss?) from a reflective roof.

Dont know what part of Colorado you are in but if vulnerable to fire a metal roof is a huge plus for this also.
posted by bartonlong at 5:13 PM on July 3, 2012

We insulated the attic of our house by extending the rafters with effective 2x6's (2x4 boards with 1/4" plywood to connect them to the rafters with a 2" air gap), adding fiberglas batts, then putting polystyrene boards over that as a combination air barrier and extra insulation, and finally finishing with 2x10 boards. It's much warmer in winter and cooler in summer, the finished ceiling makes the room a pleasant space when combined with pre-existing high ceiling in the centre and already finished floor, and a similar technique worked for the end walls.
posted by thatdawnperson at 6:12 PM on July 3, 2012

IMO, the first thing you need is tent over your attic stairs. You say you can't use one - why? Because the store bought ones don't fit your opening? You don't need no stinkin' store, you can do it yourself. The best attic stairs tents are home made. Foam insulation board, metal tape, caulk, and a knife - that is all you need. (Actually, with your big opening, I might make some simple support wall out of plywood to make it more solid, and then glue the isulation board to the the plywood.)

Yes, foam board only has an R7 rating, but you can stop the draft doing this, and that is incredibly important. No matter how well you insulate the attic, it will always be a bit hotter, and that hot area will always draft out of the staircase. It is just a matter of how hot is the air - or you can seal the draft. You can make an insulation tent. Use lots of tape and caulk. Seal the draft.

Also, another key thing is an attic fan. You might need to get an electrician to install this. But, you can set it to a certain temperature, and if the attic reaches that temperature, the fan will help vent the attic and circulate the air. Attic fans work really well if probably installed.

Also, I agree with the folks above about checking with your local utility and government, there may incentives for energy conservation. Here is a partial list of rebates and incentives available in Colorado.
posted by Flood at 8:08 PM on July 3, 2012 [1 favorite]

Thirding that you need to decide if the attic is inside the building envelope it not. To make this decision, you need to look at how the space is ventilated. What you want is, from the top down, roofing, air space open to the outside, insulation, vapor barrier, conditioned space (ie inside of the house). The air space can be the whole attic, or it can be as smaller area between the roof and the insulation. Just adding insulation is unlikely to be as effective as a well planned system and it may cause problems (eg ice dams in the winter). If you don't want to use the attic space as living space, it would be best to insulate the floor, but you still bed to make sure you have proper ventilation.

You may want to have someone knowledgeable have a look before going ahead.
posted by ssg at 9:15 AM on July 4, 2012 [1 favorite]

Seriously consider having a contractor to do spray foam on the ceiling of the attic (you'd take down the existing stuff, and possibly put it back later). It may seem like a lot of money - several thousand - but I know from experience, that simple attic retrofits on an old house can turn into a fucking nightmare.

I know this personally. My house was built in 1930. (Dunno how old yours is.) I easily ended up spending the amount it would've cost to have seriously thick spray foam, but instead, it took 3 months instead of two days.

In the meanwhile, if you have two windows (or one and are ~certain~ you have working, unblocked soffit vents) get one of these, mount it in the open window and set it to go on at 100 degrees (or whatever slightly above the expected outdoor temperature is).

And build that cover! Seriously, if building a simple cover to an unusually shaped access is too daunting, do not even begin to mess with tearing up an attic. Especially if your house is older. (Don't know why I'm getting that impression, but mine had virtually no (true) right angles when we got down to the framing - very difficult and painstaking to deal with 4x8 sheet goods that ~should(!) simply line up perfectly but don't due to framing that has settled as was spaced on unconventional intervals.)
posted by BleachBypass at 1:38 PM on July 9, 2012

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