Insulating in tight spaces and at bow windows

Q: My heating ducts are in the cellar, and the small ones that go to individual rooms are between the joists. How can I insulate them? The trunk lines (big rectangular ones) are under the joists. How can I insulate those?

A: It is difficult to insulate round ducts in the space between joists. If possible, use 1-inch duct insulation and wrap the round ducts, then buy a stapler that can staple a standing seam so you can seal the wrap. Then fill the space between joists with 6-inch fiberglass insulation. I think you can get away with stapling the paper backing directly to the bottom of the joists.

You can wrap the trunk lines, too, and if it's hard to wrap the tops, just wrap three sides, and seal with Gorilla -brand tape or staple the insulation to a joist. You have to play these things by ear.

Q: My bow window overhangs the wall by about 12 inches, and has a severe draft in the winter. I know I could put on storm windows, but they might interfere with the view. I notice the bottom of the overhang seems thick. Could I put insulation into that cavity? If so, what kind?

A: First, determine whether that space is or isn't insulated. To find out, put your hand flat on the interior top of the overhang. It will feel cold at the start, but if the space is insulated, your hand will warm up within 30 seconds. If it's not insulated, your hand will continue to feel cold because the cold surface is taking heat out of your body. If the surface is wood, this test may not work very well because wood is a pretty fair insulator. If there is no insulation, you can remove the inside cover and fill the cavity with fiberglass insulation. Or drill holes in the underpart of the overhang and have foam insulation blown in.

Peter Hotton has been The Boston Globe's "Handyman on Call"

for 30 years. E-mail questions to photton@globe.com. Sorry, no personal replies.