Insulating an antique attic
May 13, 2010 9:47 AM Subscribe
Help me save money and the planet by telling me about attic insulation?
I live in Upstate New York. The house was built around 1900, and none of the owners in the last 110 years has bothered to insulate the attic, at all. (Nor much of anything else.) This isn't exactly energy efficient, as you can guess.
Now probably what I ought to do is to hire professionals to do the whole house, including ripping off the siding, insulating the walls, then redoing the siding, replacing the windows and so on. But I just had to replace a roof, and the economy of 2010 doesn't leave me wanting to incur another huge housing expense this year. But, it occurs to me that at least I can make a start by doing something about the attic on my own.
Any of the "do it yourself" guides I see, though, sort of assume things I don't see. I can't, for example, carefully trim rolls of insulation to fit between the rafters, because someone 50 or 60 years ago put down some plywood flooring over most of it. So I'll have to sort of stray from the beaten path. My thought was that if I simply cover every accessible inch of attic flooring/rafters with fiberglass rolls or batts, (being careful not to have anything touching any sort of chimney / exhaust) my solution will be imperfect -- but far better than the "nothing" I have now.
Am I missing something in thinking that way? Is there some way that this ends up being no real use at all, or worse yet, somehow harmful or dangerous?
I live in Upstate New York. The house was built around 1900, and none of the owners in the last 110 years has bothered to insulate the attic, at all. (Nor much of anything else.) This isn't exactly energy efficient, as you can guess.
Now probably what I ought to do is to hire professionals to do the whole house, including ripping off the siding, insulating the walls, then redoing the siding, replacing the windows and so on. But I just had to replace a roof, and the economy of 2010 doesn't leave me wanting to incur another huge housing expense this year. But, it occurs to me that at least I can make a start by doing something about the attic on my own.
Any of the "do it yourself" guides I see, though, sort of assume things I don't see. I can't, for example, carefully trim rolls of insulation to fit between the rafters, because someone 50 or 60 years ago put down some plywood flooring over most of it. So I'll have to sort of stray from the beaten path. My thought was that if I simply cover every accessible inch of attic flooring/rafters with fiberglass rolls or batts, (being careful not to have anything touching any sort of chimney / exhaust) my solution will be imperfect -- but far better than the "nothing" I have now.
Am I missing something in thinking that way? Is there some way that this ends up being no real use at all, or worse yet, somehow harmful or dangerous?
If it is just plywood, can't you pull up sections to put in the rolls before subsequently replacing the plywood?
posted by mmascolino at 10:32 AM on May 13, 2010 [1 favorite]
posted by mmascolino at 10:32 AM on May 13, 2010 [1 favorite]
I was in a similar situation this past winter, living in a house with no insulation in the attic. After building little cages out of chicken wire to keep insulation away from junction boxes, light fixtures, etc., we just rolled out batts of insulation covering the entire floor of the attic. It's probably not perfect but the difference in heat retention was noticeable within a couple of days.
posted by xbonesgt at 10:47 AM on May 13, 2010
posted by xbonesgt at 10:47 AM on May 13, 2010
One of the problems with insulating old houses is airlfow and venting. Whatever you do you need to maintain adequate venting, which means keeping existing vents clear. Something that does usually work pretty good is spray foam on the bottom of the roof in the attic space. It forms a vapor barrier and keeps the condensation away from the attic interior, but first you must seal the attic (and whole house really). This is usually over half of the heating saving alone. This means doors and windows that tightly seal, soffits that are closed tight and so on. You can hire a professional with the right equipment to come look at your house, get an estimate for various levels of improvement (it will probably follow the 80/20 rule or a little effort will go a long way with further gains require more effort). this shouldn't cost too much up front and will give you a plan of attack you can implement over time as money allows.
BTW this is about the best return on money you can get right now for the easy, low cost initial steps, and sealing and insulating the attic space is not that hard. After sealing the big air leaks i would use a combination of spray foam around the eaves/soffits and agaisnt the roof with blow in insulation after removing the plywood. Insulating the walls takes a lot of effort for less gain than fixing the roof and sealing windows and doors better will give you for way less money.
posted by bartonlong at 10:51 AM on May 13, 2010
BTW this is about the best return on money you can get right now for the easy, low cost initial steps, and sealing and insulating the attic space is not that hard. After sealing the big air leaks i would use a combination of spray foam around the eaves/soffits and agaisnt the roof with blow in insulation after removing the plywood. Insulating the walls takes a lot of effort for less gain than fixing the roof and sealing windows and doors better will give you for way less money.
posted by bartonlong at 10:51 AM on May 13, 2010
You can also blow insulation into the walls, which you need in frigid windy upstate NY- I lived in Ithaca for 20 years..
You need to figure out if you want to use the attic. If you do, you need to keep the plywood floor, otherwise you will fall through the floor/ceiling of the room below.
You can remove the plywood and put insulation between the floor joists. This will keep a lot of heat from going to the attic, and you can put the plywood back over the joists and insulation. Or you can decide not to use the attic at all, put insulation down on top of the floor and never go up there.
Another option is to insulate the inside of the roof. You could put insulation between the rafters. Next winter, if you look, you'll see that the heat still goes through the wooden rafters and the snow will melt accordingly, leaving an interesting pattern on the outside of your roof.
Yet another option would be to cover the inside of the roof with rigid foam insulation of some sort attached to the rafters. The advantage of this is that it insulates the rafters and the roof and you won't get the weird melty pattern I mentioned above. The disadvantage may be that rigid foam insulation is, or at least used to be, made out of some weird shit.
Insulating is not as simple as it might look. You need to make sure you allow for ventilation and for condensation to escape. Go to your local library and see if they have any books.
Good luck!
posted by mareli at 10:52 AM on May 13, 2010
You need to figure out if you want to use the attic. If you do, you need to keep the plywood floor, otherwise you will fall through the floor/ceiling of the room below.
You can remove the plywood and put insulation between the floor joists. This will keep a lot of heat from going to the attic, and you can put the plywood back over the joists and insulation. Or you can decide not to use the attic at all, put insulation down on top of the floor and never go up there.
Another option is to insulate the inside of the roof. You could put insulation between the rafters. Next winter, if you look, you'll see that the heat still goes through the wooden rafters and the snow will melt accordingly, leaving an interesting pattern on the outside of your roof.
Yet another option would be to cover the inside of the roof with rigid foam insulation of some sort attached to the rafters. The advantage of this is that it insulates the rafters and the roof and you won't get the weird melty pattern I mentioned above. The disadvantage may be that rigid foam insulation is, or at least used to be, made out of some weird shit.
Insulating is not as simple as it might look. You need to make sure you allow for ventilation and for condensation to escape. Go to your local library and see if they have any books.
Good luck!
posted by mareli at 10:52 AM on May 13, 2010
you'll see that the heat still goes through the wooden rafters and the snow will melt accordingly, leaving an interesting pattern on the outside of your roof.
No offense to mareli, but careful with the options that keep some parts of your roof warm while others are cold -- that is the road to damaging ice dams and excessive icicles. In an ideal universe your attic is as cold as the outdoors, and your effective heat barrier is between your living space and a well-ventilated cold attic.
Also, most guidelines I have seen prioritize insulating your attic floor, then sealing drafty air leaks around windows and other wall penetrations, replacing old windows if they are drafty, then filling wall cavities with blown-in insulation. I've had it explained to me that since heat rises the in-wall insulation isn't as important as attic insulation. Good luck!
posted by aught at 12:24 PM on May 13, 2010 [1 favorite]
No offense to mareli, but careful with the options that keep some parts of your roof warm while others are cold -- that is the road to damaging ice dams and excessive icicles. In an ideal universe your attic is as cold as the outdoors, and your effective heat barrier is between your living space and a well-ventilated cold attic.
Also, most guidelines I have seen prioritize insulating your attic floor, then sealing drafty air leaks around windows and other wall penetrations, replacing old windows if they are drafty, then filling wall cavities with blown-in insulation. I've had it explained to me that since heat rises the in-wall insulation isn't as important as attic insulation. Good luck!
posted by aught at 12:24 PM on May 13, 2010 [1 favorite]
You should be able to insulate right up to your chimney - anything inside the house should already be double insulated (if it's not, it's dangerous and should be replaced). An old brick chimney, for example, is fine to have insulation touching it.
I'm assuming that you don't plan on using the attic for storage or living space. If that's the case, I'd consider pulling up the plywood that is there.
Once you have the plywood up, you want to seal as many air leaks as you possibly can - get some cans of sprayfoam and look for penetrations through the attic ceiling (sewer vent pipes, wires). Spray foam the heck out of these. For electrical boxes (not pot lights) you can cut pieces of vapour barrier, run a bead of butyl caulk around the box and stick the vapour barrier down.
If you have potlights, you need to figure out if they are "IC" for insulation contact - if they are, you still need to seal them - you can buy big blue "boots" to go over IC potlights. Non IC potlights need to be protected according to manufacturers guidelines (usually a metal box that can cover them)
Now you need to make sure that you can leave a clear path from your eve vents (if any) up along the underside of your roof. You need "Attic Baffles" to do this - these bits of cardboard attach to the outside of your top plate to ensure airflow into the attic.
Once this is all done, I'd suggest you go with a blown in insulation product - costwise it's about the same as batts, and you can be much more thorough. Most building centers will rent you the blower, it's a pretty simple DIY job. You'll want at least 12" of blown in added.
posted by davey_darling at 1:45 PM on May 13, 2010
I'm assuming that you don't plan on using the attic for storage or living space. If that's the case, I'd consider pulling up the plywood that is there.
Once you have the plywood up, you want to seal as many air leaks as you possibly can - get some cans of sprayfoam and look for penetrations through the attic ceiling (sewer vent pipes, wires). Spray foam the heck out of these. For electrical boxes (not pot lights) you can cut pieces of vapour barrier, run a bead of butyl caulk around the box and stick the vapour barrier down.
If you have potlights, you need to figure out if they are "IC" for insulation contact - if they are, you still need to seal them - you can buy big blue "boots" to go over IC potlights. Non IC potlights need to be protected according to manufacturers guidelines (usually a metal box that can cover them)
Now you need to make sure that you can leave a clear path from your eve vents (if any) up along the underside of your roof. You need "Attic Baffles" to do this - these bits of cardboard attach to the outside of your top plate to ensure airflow into the attic.
Once this is all done, I'd suggest you go with a blown in insulation product - costwise it's about the same as batts, and you can be much more thorough. Most building centers will rent you the blower, it's a pretty simple DIY job. You'll want at least 12" of blown in added.
posted by davey_darling at 1:45 PM on May 13, 2010
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posted by leetheflea at 10:21 AM on May 13, 2010