insulating a room
February 12, 2008 11:05 AM   Subscribe

RenovationFilter: I live in the top floor of a historic building. I have a small section on the sloped ceiling where the original planks are visible. One problem is that there are spaces between the planks, an inch or into the spaces is the actual roofing material. As you can imagine this is hardly energy efficient. I'd like to "plug" up the gaps but leaving the sections of planking exposed for aesthetics. Does anyone know how I could do this? I'm imagining there's some kind of black spray foam insulation I could spray in there that would expand to fill it, and not be too visible, but I'm not sure if there is, or if this works. Any recommendations for tips or specific products is highly appreciated.
posted by dearleader to Home & Garden (17 answers total) 1 user marked this as a favorite
can you feel cold air there? You could use some dark colored caulk and carefully fill in the cracks if they are not too wide. get some caulk that matches the color up there, or you could use black tar to do it, that would be a messy task. do you own this place, or just rent? Might want to consider what the landlord would think of doing this before moving forward

and if you use tar, cover your floor while you do it!
posted by Salvatorparadise at 11:09 AM on February 12, 2008

Maybe you could rip some small strips of wood to fill and match.
posted by rhizome at 11:13 AM on February 12, 2008

Can you give us some indication where you are located? How you insulate/seal is very different in different climates.
posted by ssg at 11:16 AM on February 12, 2008

Response by poster: I do own, I can feel some air (spaces are about three-quarters of an inch), and I'm in cold, somewhat humid Northeast... thx
posted by dearleader at 11:31 AM on February 12, 2008

As an aside, beware of expanding foam sprays. Some of those buggers have enough power behind their expansion to fracture a 2x4 if you were to, uh, mistakenly spray them into an enclosed area. Surprised the hell out of me. Fortunately the thing I was building wasn't historic.

On to the topic at hand, the caulking/sealing universe have some lovely cylindrical foam "rod" materials that may work here. Get the right diameter, stuff it up in your gaps, apply the appropriate caulk to the front side.
posted by aramaic at 11:37 AM on February 12, 2008

These guys would know how and with what materials to solve your problem. Good luck and stay warm.
posted by watercarrier at 11:44 AM on February 12, 2008

Hm, are you saying you can see the back side of the shingles between the planks, like in your living space?
posted by d4nj450n at 11:46 AM on February 12, 2008

I agree that knowing your climate is key to answering correctly. Also, what are you trying to achieve?

Assuming that you live either in a cold or hot climate and your primary goal is energy efficiency:

If you feel air moving through the cracks then I agree that you should try to fill them.

However, considering that these planks are the underside of your actual roof, the only way to really achieve energy efficiency would be to actually insulate the ceiling/roof by putting insulation between the joists, thereby covering your planks (or ripping up the roof and insulating from above).

How wide are the cracks? The width of the cracks will determine the product you'll want to use.

How high is the ceiling? If you have a 15' ceiling you can get away with a lot more than if you have an 8' ceiling, just because you can't really see it that closely.

How are the planks finished? I'm guessing they're not painted. How important is the finished appearance? If you really want it to look nice, and the cracks are thin, you can use a wood filler in between the cracks and refinish the whole thing to match.

Generally, I think painters caulk or expanding foam could both work (depending on the width of crack). Caulk would probably be easier to control. I would definitely not use tar. Too mess, too smelly, not intended for this purpose.
posted by ssimon82 at 11:52 AM on February 12, 2008

Ropes dipped in varnish is a traditional filler.
posted by glibhamdreck at 12:01 PM on February 12, 2008

Tom Silva replies: You can apply wood filler to fix the gaps, but this can be a temporary fix. When the floor contracts, the filler can pop out; or, when it expands, it can fall in, unable to span the wider gap. In the Milton House, the gaps in the floorboards were so wide that we filled the seams with rope and then stained it to match the floor. This is an old technique that's quite smart; the rope expands and contracts with the rest of the floor and the gaps stay plugged, keeping drafts to a minimum. To properly fix your problem, you need to determine why your floors are gapping
posted by glibhamdreck at 12:03 PM on February 12, 2008 [1 favorite]

Just a follow-up since you answered while I was typing.

The cylindrical foam rod is called "backer rod" and I think that's the way to go. If the space above the planks in 1" then you'll probably want the 1-1/2" backer rod. Shove it up there so that the backer rod is pushing against the *back* of the planks, so you can put the sealant *between* the planks. You'll want a good 1/2" thickness of sealant at least to ensure it doesn't just peel off. You might want to apply it in two coats. You can get in it a ton of colors.
posted by ssimon82 at 12:03 PM on February 12, 2008

tom silva is the MAN
posted by Salvatorparadise at 12:27 PM on February 12, 2008

Response by poster: thanks for all these great answers. yes, the underside of the roofing material is actually visible between plank gaps (in two 'window like' sections). this is where the bulk of the coldness/heat comes from -- some as well from the planks too, but not as much. I realize it's an energy efficient nightmare (but the planks, stained, looks great!)
posted by dearleader at 12:30 PM on February 12, 2008

Plugging up the cracks may not be worth the trouble. R-value is a measure of the efficiency of insulation. A large R-value is good. The wood planks (assuming 1 inch thick) have an R-value of only about 1.25. Insulation you place between the cracks might have an R-value of 3 or 4. So even if you plug up the cracks, most of the heat is going to go right through the exposed planks since they have more surface area than the cracks. The only practical way to provide useful insulation is to cover the planks as well as the cracks. If you don't want to do that for aesthetic reasons, it probably isn't worth worrying about the cracks unless there is actually an air draft coming through the cracks.
posted by JackFlash at 12:35 PM on February 12, 2008

There's a spray insulating product that expands a lot to fill nooks & crannies. You'd have to practice to get good control of the amount. It's beige. Visit a good hardware store.
posted by theora55 at 12:40 PM on February 12, 2008

It sounds like you are probably losing a large amount of energy through this section of uninsulated roof. I'd recommend you get someone experienced to have a look at it in the context of your whole apartment to give you an estimate of the cost of the energy you are losing through this section. How is the rest of your ceiling insulated?

Since you are attached to the look of the planks, would you consider faking that same look below a proper layer of insulation? I'm not sure what your planks look like, but it probably wouldn't be prohibitively expensive to buy some similar wood, stain it, and attach it to some framing designed to hold sufficient insulation (plus some air space and a vapour barrier depending on the configuration of the rest of your ceiling).
posted by ssg at 1:09 PM on February 12, 2008

dearleader writes "I can feel some air (spaces are about three-quarters of an inch), "

Use a 3/4" foam backer rod (the rod just needs to be tight enough to stay in place) and then apply a latex caulk over top. You won't be able to stain it but it comes is a dozen or so colours and some of it can be painted. Good Latex caulk will stretch upto 2x so you don't have to worry about it cracking.

You might run into the problem of your planking being thinner than the gaps in which case the foam will be proud of the boards. If that's the case you can place a wide bead of caulk in the crack and then use it to hold a smaller backer rod. Then fill in the gaps with more caulk. This is acceptable practise because the foam is just being used to reduce the amount of expensive caulk used.

Rope might look good but it would take approximately two times forever and wouldn't block the draft (note Tom was talking about a floor where you could really pound rope in to pre-compress it; do that on your roof and you'll force the planks off your framing).

However as you're in NY rather than Hawaii ssg's suggestion is the approach I would take using caulked extruded polystyrene insulation so you don't have to worry about a plastic or latex moisture barrier (practically impossible to get right in these renovations).
posted by Mitheral at 7:01 PM on February 12, 2008

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