Air Sealing to Cut Energy Costs – Attics

If you missed part one … tough cookies … no, just kidding … it’s at

OK, this time around I’m going to concentrate on plugging up the top … Sealing up the thermal envelope along the ceiling and attic plane. By thermal envelope I mean all the surfaces that separate heated (aka; conditioned) space from outside (aka; ambient). It usually follows the insulation, but not always. Sometimes it may be the attic floor, sometimes the roof rafters themselves, sometimes a combination of both.

Now, there are two major ways you lose heat out the top. One is through conduction … The air inside warms up the ceiling itself … the heat conducts through the drywall and wood … and then it dissipates off outside. Good insulation will stop this from happening, But I can spend hours talking about insulation, so I’ll leave it for another post. (I can spend hours talking about watching paint dry … like I said before, I don’t get out much)

The second way is through air leakage. Insulation “don’t do diddly” to stop air leakage. Here, the warm inside air just leaks out through holes in the ceiling and cold outside air leaks in somewhere else. The bad news is … you lose a heck-of-a-lot of heat through a really small hole. The good news is … you can plug ’em pretty cheaply.

First off, we need to look at every ceiling that meets the attic (I’ll talk about finished attics later on). Start in the closets with a flashlight, they are often neglected from day one. Look along the ceilings for gaps and holes. Sometimes old phone and tv wiring left holes, sometimes the drywall was never taped and spackled at all. Anything you find should be caulked or taped so that no air can get through. (we aren’t worried about insulating at this point, just stopping air flow.

Oh yeah, by the way… stuffing fiberglass insulation in the cracks is a bad way to go, air still flows right through the fiberglass. Use tape, spackle, caulk, expanding foam … what ever you feel like … as long it stops air. I like using the expanding foam. It expands, drips, drops, splashes and generally coats all of my exposed skin long before the holes are filled. …And picking it out of your hair is a wonderful weekend chore.

Next, look around for ceilings with crown molding. See if you can tell if the drywall is completely closed behind it. Sometimes you can tell from the attic, you’ll see light shining through the cracks. Even a really really thin space around an entire room will have the same effect as one hole the size of your fist. It adds up quick.

Attic hatches and attic stairs are another money vacuum. Here’s some math for you (oh,stop groaning and just listen) … IF … you have a ceiling that’s 10’x10′ with R30 fiberglass batts … your effective R value is about R-18 and your heat loss is about 34 btu/hr. if you add a PERFECTLY SEALED 2’x2’attic hatch your heat loss rises to about 84 btu/hr. with a regular old piece of plywood for a hatch …. easily up to 10 times that. Consider this a MUST FIX.

An easy fix for a hatch is to add a few layers of rigid foam to the back (4″ is nice) and put some weatherstripping around the frame to seal it. Adding another layer or two of drywall or plywood will make it heavier and help press it into the weatherstrip. Sandwich it all together with some long screws or just glue it with some expanding foam. (yeah, that won’t be messy)

For attic stairs, weatherstripping is a must, Then, if your still interested, make a box out of 2″ foam that covers the whole stairway from the top and lifts off easily when you climb up. (They also make an insulated “bag” that attaches from above and opens with a zipper. E-mail me for info).

Use the same “BOX” idea to cover over a whole house fan too. (the ones with the louvers that open into the house). They are another big heat loss in the winter.

I know what your thinking … is this idiot still talking? My wife thinks we should be able to heat our house on my hot air alone.

Anyway …. almost done ….

last thing … recessed lighting… Turn them on …then go up in your attic and look for light … if there is light shining up … then ther’ be holes … and hot air always finds them holes. Usually there is also no insulation around the cans … that’s supposed to be that way to let heat escape. ( OK, so you see the problem now don’t you?). Only fix for this is to change out the fixtures for sealed ones. The sealed cans are only about 15 bucks each and should pay for themselves in one season. If you aren’t very handy and/or don’t like playing “fun with high voltage” … leave this one to a pro.

Last …last thing … Go up in the attic with a couple cans of expanding foam (everybody loves expanding foam)… seal off anywhere something comes through the ceiling and into the attic. Pipes, wires, ducts … anything you see except chimneys (they need fireproof material). Move the insulation out of the way, foam it up, then replace the insulation.

OK,OK, I lied … there is still more …well heck, you got me started …

The completely last thing …. really … no more … last …. the end …

If your attic is finished space, make sure the insulation is in the right places. If you have access to the crawlspaces behind the short knee-walls where the roof goes down (usually there is a little door or a bookcase that comes out), check to see that the insulation is continuous. There are two ways it could be done… Either the insulation will continue straight down the roof rafters all the way to where it meets the ceiling, or it will drop down along the knee walls and run along the ceiling to the outside eave. If it is down the kneewalls, take some 1 or 2″ rigid foam and cut panels to close off between the rafters where they go under the knee walls. you can glue them in with rigid foam. Otherwise, all the heat from holes and lights in the ceiling underneath will escape out and into the cold crawlspaces. And seal up the entry hatches on your way out.

OK …. now I’m done


Leave a Reply

Your email address will not be published. Required fields are marked *

six + 7 =