Q. Reusing Loose-Fill Cellulose
A blower-door test on an older home I’m renovating shows a need for some serious air-sealing. Unfortunately, a previous owner blew about a foot of loose cellulose into the attic without first addressing any of the usual sources of air leaks. Rather than shoveling cellulose out of the way and patching the leaks we can find — possibly missing some problem areas — I’m thinking of having an insulation sub vacuum up all the existing material, then seal the area with a flash layer of closed-cell foam. If we go that route, is there some way to re-use the original cellulose, or would that be more trouble than it’s worth?
A.Jonathan Tauer, an insulation contractor in Florence, Mass., responds: There’s no problem with vacuuming up and reusing existing cellulose, as long as it’s not mixed with lumber scraps, old plaster, or other debris. Insulation suppliers can provide vacuum bags large enough to hold several cubic yards of loose cellulose. The easiest way to fill them is to call in a contractor with a truck set up to install spray cellulose, which ordinarily includes a powerful vacuum used to suck scrubbed-off excess material back into the hopper for re-use. By reconfiguring the output, it can easily be adapted to fill bags instead. Another option is to rent a gasoline-powered impeller vacuum, which is something like a shop vac on steroids. Once the attic has been cleaned out, you can apply the flash coat of foam and blow the cellulose back on top of it.
But unless the attic floor is extremely leaky over much of its surface, that may not be the most cost-effective approach. You can find and seal many leaks from inside the living space by methodically working your way around it with a smoke pencil while running a blower door. Some problem areas — like vents, chimneys, light fixtures, and partitions — will have to be sealed from within the attic, and that will require some shoveling and sweeping. Such work is no one’s idea of a good time, but because vacuuming out and replacing the cellulose is likely to cost $1,500 or more, air-sealing may be a smarter use of resources. The key is to test before, during, and after the sealing process to be sure you’ve actually solved the problem.