Q: After we had a replacement window installed a couple of years ago, I sprayed foam insulation around the edges, because the installation left some noticeable gaps.

The foam expanded and is now all over the white siding. I was told to let it dry and that eventually it would deteriorate and could easily be removed. I’ve been afraid to touch it ever since, but it is an eyesore. Thankfully, it’s at the back of the house. Do you have any tried-and-true methods for removing this?

A: Kudos to you for insulating the voids. The installers should have done this. Either they didn’t do it at all, or they did such a poor job that you had to redo it.

Unfortunately you did it from the outside. You’d have been better off using a top-of-the-line acrylic caulk. It may have taken a couple of applications, but the job would have been done without the mess. But the deed is done. Not to worry; you can fix it.

Urethane foam’s main use is to plug voids in new construction, including all penetrations that might let conditioned air out or outside air in. Examples are locations where water pipes or heating ducts move from the crawl space or the attic into the house or to seal cracks at door and window penetrations.

To seal potential air leaks around windows, urethane foam is sprayed between the window and the wood framing. Spray the foam about halfway from the outside edge of the frame and let expansion take care of the rest. Fill the void too much and the foam will seep beyond the inside edge of the window and you’ve got a sticky, gooey mess.

Anyone who’s made a misstep with canned urethane foam insulation knows that as the stuff expands, it goes into places where it’s not supposed to go. Whether it cures to a hard surface or remains flexible, it’s a bear to get off. The best you can do when it’s wet is to have a can of acetone nearby and clean up the mess with this solvent. Acetone is the same as nail polish remover, so it’s strong stuff.

But in your case, a couple of years is more than enough time for the insulation to decompose. It’s been exposed to the sun, wind and rain, and it probably has the consistency of a rice cake.

Use a putty knife pressed against the window to score the insulation where it’s oozed out. Then press the putty knife against the siding and score the foam from that side. Then you should be able to remove the bulk of the insulation.

If the siding is painted wood, sand the residue off with 100-grit sandpaper. You’ll have to do a little touch-up painting.

If the siding is vinyl or aluminum, use an abrasive sponge to scour the remaining residue from the siding.

In either case, finish the job by properly caulking the joint with acrylic latex caulk.

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