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 air ducts of my home 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.
Fiberglass Insulation Roll
The “carpenter” who previously owned my home didn’t like to finish projects – like this half-insulated heat duct.
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 candy cane 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.
While the fiberglass roll of insulation definitely had the R-value I would have liked, I found that it was simply too difficult to wrap around existing ducts that were secured and attached relatively close to the floorboards overhead.
Another option would have been to simply place fiberglass insulation bats between the floor joists and insulate one side of the round heating ducts. I liked that idea, but it wasn’t really a complete solution because I’d still end up losing a lot of heat through the uninsulated top of the duct. I might even end up with weird “warm spots” on my floor along where the heating ducts ran beneath.
Foil Duct Insulation
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. That bubble-wrap look is the secret to how it works: Those little foil bubbles have tiny pockets of air in them (much like fiberglass has pockets of air in it) and the air acts as an insulator between my cool basement and the warmth of the metal heating duct.
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.
Essentially, I did not wrap the heating ducts like a candy cane, but rather, laid the insulating foil over the ducts like a blanket. I then closed the blanket along the bottom of the 4 inch round heating ducts with the foil tape.
Sealing Leaks
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 was caused by a floor nail that had been driven in too far. Hot air was shooting out that hole for 50 years until I took a piece of foil tape and wrapped it around the duct, sealing it up again.
While I was insulating my ducts and finding little problems here and there, I decided to take an hour or so and conduct part of my own little do-it-yourself home energy audit on my heating trunk and main ducts. I grabbed my roll of foil insulating tape and an incense stick and got to work.
I lit an incense stick (the smoky kind) and very gently moved it along my heating ducts, looking for any strange patterns in the smoke. If you see the smoke being pulled towards a duct or being blown away from a duct then you can bet there’s some sort of leak or pin hole. I found four different leaking points of air through my ducts this way in a matter of just a minutes!
Once you find a leak they’re usually pretty easy to plug up. Just run a piece of foil tape across the hole or leak and smooth it down hard with your hand or finger, making sure there are no ripples in the tape and no more leaking air. You can check the air flow again with the incense stick to be sure the leak is sealed.
End Results
About a day after insulating the heating 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. A temperature reading confirmed that a few areas of the basement were one to two degrees cooler than they had been a few days before even though the weather was the same and the heat settings hadn’t been touched.
I was searching for \”energy saving\” related blogs and found your wonderful creation.
You have a gold mine of useful information.
A link to your blog will soon appear on my blog.
Hope you will return the favor after checking it out.
Birney Summers
Energy Boomer
bksummers@att.net
http://energyboomer.typepad.com
[...] Keep It Checked: Okay, I’m pushing the heading style, but you’ll want to check a couple different things on your AC about once a month. You’ll want to check your air filter and replace it a little more than usual. Some sites recommend replacing it once a month, but I think that might be a little over zealous. My filters cost me nearly $20 a piece and the manufacturer suggests changing them every six months. I usually end up changing them three or four times a year as I see a need. Besides the filter, you’ll also want to look around for any leaks in the hoses or air ducts. You’d be shocked at how often you’ll find loose ducts with small gaps and tiny air leaks around older duct work. You might also consider insulating your home’s air ducts which will not only help with heating, but also on cooling. [...]
Where did you get the 12″ insulation?
Bill,
I picked up the 12″ insulation at my local mega-hardware store. I still have a roll and a half of it :-)
If you can’t find it, then you might want to try buying your air duct insulation online
. It’s cheap, you have lots of options and it’s light enough to be shipped without too much trouble. Good luck!
I was about to do this exact same thing. Do you think it was worth it? Did you notice a difference in the heating bill gas/electric?