First time living in a house. While I was cleaning (AC was also running) I noticed that somewhat cold air leaks from the circled part of the furnace on either sides.

Not sure if this this information is relevant: My electric company shows usage comparison to neighbors (mostly town houses), it says I am about 30-40% higher than my neighbors.

Is this normal for air to be leaking here? Should I do anything about it?


  • Kinda puzzling that the previous owner clearly saw the need to tape parts of the system, but not others. Jun 24 '20 at 14:01

"duct tape" - this is what it is actually designed for! Though actually I would use a good metal tape like:

enter image description here

However, would that explain 30% difference in energy usage? No. Maybe 1%, if that, since any leaked air is still going into your house and not to to the outside.

The typical utility company comparison is based on very broad comparisons. At best, they will compare single-family-home to single-family-home and townhouse to townhouse. I've never seen any that actually take square footage or other factors into account.

Your 30% difference could easily include one or more of:

  • electric vs. gas hot water
  • electric vs. gas heat
  • electric vs. gas kitchen appliances (e.g., I have a gas cooktop, but the house originally had electric and most of my neighbors still do)
  • number of people in the house (more people = more computers, lights, cooking, etc.)
  • typical temperature setting for air conditioning and whether you set back the temperature during the day (well, in the old days when people went to school or worked outside the home...)
  • quality of windows
  • lighting - incandescent vs. fluorescent vs. LED

and many other things. Bitcoin mining in your basement?

  • 1
    My energy supplier in the Netherlands asks the following items for the comparison: Type of house (apartment/house etc and location relative to the roof), building year, m2 and the number of inhabitants. I don't know if they actually use this in the comparison though...
    – ROIMaison
    Jun 24 '20 at 7:45
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    Note that "duct tape" is ironically a poor choice because it doesn't adhere well to ductwork. Foil tape is the right answer for ductwork.
    – Machavity
    Jun 24 '20 at 12:51
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    Yeah, I get those "compared to your neighbors" things too. If I were concerned, I'd turn off the 2 file servers and 5 other computers, but having them on is of higher priority. I guarantee the neighbors have more TVs than we do, though... In general, those compare apples to draft horses and aren't all that useful.
    – FreeMan
    Jun 24 '20 at 13:13
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    No, you're quite right. Duck is an entire brand of tape
    – Machavity
    Jun 24 '20 at 14:00
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    Actually, "duct tape" is more properly described as "duck tape" (because it's traditionally based on "duck" fabric) and is intended for sealing metal ammunition canisters, not ducts.
    – Hot Licks
    Jun 24 '20 at 14:56

Your notification that you are targeted to be using 30% to 40% more energy than your neighbors is interesting information but probably is a poor comparison since there are so many factors that can lead to your total consumption. Any of the following could apply plus others we cannot guess.

  1. You run your AC more than the neighbors.
  2. You are running an electric car charging process every day or so.
  3. You have electrical powered heat, cook stove, water heater, or cloths dryer whilst neighbors are using natural gas appliances.
  4. You are using lots of bright incandescent and halogen light bulbs when the neighbors have converted over to all LED lighting.
  5. You are running high power tools like saw tables, jointers, lathes, planers, grinders in your shop.

To really decide if the cold air leak on your furnace is a problem you could cover that crack (opening) with duct tape and see if that results in a more effective use your AC cooling the other parts of your house.

Your furnace filter is probably behind that lower metal lid. You may want to investigate the air filter. If it was all clogged up with dust this could be causing an increased pressure in the forced air unit and causing more cold air to leak out than it would with a clean filter.

  • Thanks a lot Michael, I just replaced my AC filter to 1900 3M filter a week back. Jun 23 '20 at 23:00

Leaking air is insignificant. Find something else to worry about.. Refrigeration Tech 30 years

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    Hello, and welcome to Home Improvement. Thanks for the answer; keep 'em coming. And, you should probably take our tour so you'll know the details of contributing here. Jun 24 '20 at 19:40

I've never heard of that. I'd put some duct tape on it for your peace of mind and move on.

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