7 posts / 0 new
Last post
Closed Cell Insulation

This week's ATOH episode showed the installation of closed cell insulation in the roof rafters of an attic. I have previously seen this done in other shows, but a baffle was used to space between the roof sheathing and the insulation. I've assumed that is in case there is a roof leak, but this wasn't used on ATOH. Is this baffle not necessary? I'm planning an insulation project and debating on Closed over Open cell (I understand the benefits). But I have a 70 year slate roof and am hesitant to seal the rafters without this baffle. I live in Richmond, VA, a pretty mild climate, so the benefit of Closed cell may not even be necessary. Any advice is appreciated.

Re: Closed Cell Insulation

the use of foam has absolutely nothing to do with a roof leak.. in regards to your question your best bet is to contact a local insulating company that does spray foam installs. their sales guys will know all the specs, even contact a high end renovation company and clearly ask them what they think of the product and if its ok to use in the attic space

Re: Closed Cell Insulation

You use the baffle for ventilated attics. Almost all attics are ventilated. This particular attic was sealed and not ventilated, so the baffles were not needed.

This type of "conditioned space" attics are starting to gain attention, particularly in new construction.

Re: Closed Cell Insulation

I used open cell in mine. Couple reasons. 1) cost 2) I didn't want to "place a bag" over the top of my house and potentially trap in moisture. I figure it was probably meant to breathe a little originally as was the whole house. I didn't want to alter the envelope too significantly. 3) if there is a leak, I might get some notice. Although is reality, by the time water made it to the attic ceiling, a large section of wood sheathing would probably be too far gone already.

Another advantage of closed cell is that it actually provides some structural strength to the roof structure. It has the ability to provide some amount of bracing between the joists.

IN hindsight, I think I would have gone ahead and done closed cell. I do seem to get a fair amount of humidity migrating into the attic in summer. Although some of that might be air leaks that weren't sealed completely at the sill plate.

One lesson I learned is to remove all old insulation first... don't be cheap. The old insulation made it tricky to properly install the spray foam near the ends of the roof. OF course removing the old nasty loose fill junk would probably have cost almost 1/2 as much as I paid to have it spray foamed.

Re: Closed Cell Insulation

This is one of the things that we have been thinking about doing in our house. However, I have yet to get quote and was wondering if anyone can provide a good idea on the cost difference between fiberglass and closed cell foam.

We have a very large attic that we want to be able to use for storage space, and we have a furnace up there on the second floor that seems to act differently because it is in an unconditioned attic.

Re: Closed Cell Insulation

Pretty substantial. Spray foam is probably about 50% more expensive. But it seals air leaks, so it's hard to directly compare the two. Also, if you have a furnace or air handler in the attic, insulating the roof deck brings the equipment inside the conditioned space. That saves a LOT on heating and cooling costs. Foaming the roof deck also makes the attic more usable for storage and accessible for future renovations like adding or changing electrical fixtures, plumbing, piping, rewiring and so on.

Finally, remember that if there is air movement, fiberglass does not perform as well a foam. Realistically, you can compare R20 spray foam to R 30 or even R40 fiberglass in real world performance.

Re: Closed Cell Insulation

I live in Manakin Sabot and built a house 1 year ago. I have a conditioned crawl space but wanted a conditioned attic as well but funds didn't allow me to. I know that baffles are not used in a conditioned attic because there are no vents. I had Jimmy DeKraft(sp) from Layman Brothers do my home and they did a WONDERFUL job. 804-485-6097 maybe he can help you.

Sponsored Stories

TV Listings

Find TV listings for This Old House and Ask This Old House in your area.