The “carpenter” who previously owned my home didn’t like to finish projects - like this half-insulated heat duct.

It’s only gotten cold here on the East Coast in the past two weeks so I really wasn’t thinking about how efficient my forced air heating system was until I really had depend on the heat every day and night. I knew that the previous owner (supposedly a carpenter by trade) had begun to insulate the ducts but for some reason never finished. I found more than one line of duct work in my unfinished basement that was only half-insulated, leaving bare 4″ aluminum duct the rest of the way.

I had never really worked with insulation much before this project, so I went out a bought a small roll of traditional fiberglass insulation. I figured it would be relatively easy, just shoving the insulation up there and wrapping it around the bare ducts, putting up small pieces of tape as I go and then taping the whole thing once it was in place.

That was the plan. Things didn’t go well.

The 12 inch wide fiberglass insulation was just a half inch too short to bend around my 4 inch ducts, so I tried wrapping them around like a ribbon on a candycane but there isn’t much room between my ducts and basement ceiling. While I was struggling on a step ladder with 10 feet of insulation I found myself going blind every 30 seconds as my goggles fogged up due to the face mask I was wearing. I wear glasses so everything fit poorly and after about 20 minutes of struggling with a cloud of fiberglass in the air and about 4 inches of ducts covered I just gave up and figured there had to be a better way.

About a week later I found the better way: foil covered insulation! I found it at my local hardware mega-store. Foil insulation is a little more expensive per package, but I figured it to cost about the same as regular fiberglass insulation when I sat down and figured out the price per square foot.

All insulation (and any building material) has an “R-Value” which measures the “thermal resistance” or amount of heat/energy which can flow through it. The higher the R-Value, the better the insulation. The fiberglass insulation with a foil backing that I started using had an R-value of 3 and the foil covered insulation I picked up had the same when wrapped around ducts, so that was all I needed!

Foil insulation beats traditional fiberglass insulation in ease of installation.

The foil insulation that I picked up looks just like bubble-wrap made from aluminum foil. Not surprisingly, when I cut a sheet of it off the roll that about all it really is: bubble-wrap with foil on both sides. It’s much thinner and less bulky than fiberglass insulation and its about a hundred times easier to wrap around my ducts.

So that’s what I did: I’d cut it a strip of foil insulation that was about 13.5 inches wide and then take it down the length of my ducts and just tape it on both sides, then move towards the center and place a few more pieces of foil tape to keep it in place. Then I’d take a long strip of foil tape down the bottom of the wrapped duct, covering the edge of the insulation.

Because I couldn’t see the top of the ducts, I ran my hands over them slowly, looking for any cuts or holes. Sure enough, I actually found a hole that I image was caused by a floor nail that was driven in too far. Hot air was shooting out of it until I took a piece of foil tape and wrapped it around the duct, sealing it up again.

About a day after insulating the ducts I went back down to the basement and it definitely felt a little cooler down there, telling me that less heat was escaping into my basement and more heat was being pumped into the living area of my home.