We live in CT -- so cold winters. I don't know all the right/technical terms, but this is our situation:

  • Split level ranch (two floors plus attic)
  • Gas furnace and gas water heater in the basement
  • Air handler in the attic
  • Air condenser thingy outside
  • Our attic is not used for anything. We have a few boxes (like 5) and some empty suitcases.
  • I am told we have a vented attic -- whatever that means
  • There is insulation under the floor of the attic (between the attic and top floor) but very little.
  • There is no insulation in the ceiling of the attic between the rafters.
  • We have a whole house fan thing. There is a fan on the side of the house in the attic. There is a vent in the ceiling of the upstairs hallway. When it's nice outside, I turn the AC off, open some windows, and turn on the fan. It pulls air in from outside and through the house. It works great. I plan on insulating the vent and putting a box around the fan for the winter when we're not using it.

My understanding is that water/air/something goes from the furnace or air condenser to the air handler which blows hot/cold air to the rest of the house.

So the air handler is exposed to whatever temperature the attic is. I went to the attic right now and it's pretty cold -- cause it is cold outside.

Now, what I am wondering is, should the air handler be in an insulated attic because then it wouldn't have to work so hard? Will the lack of insulation hurt the air handler? Or does it not matter?

  • If it is cold outside, then my heat is on, and the air handler would be blowing hot air -- but the attic is cold so the air handler would be surrounded by cold air.
  • If it is warm outside, then my AC is on, and the air handler would be blowing cold air -- but the attic is warm so the air handler would be surrounded by hot air.

I'm not worried about insulating the attic. I want to prolong the life of the air handler. So if my setup is not good because the air handler is exposed, then I'd like to know so I can put insulation in the rafters.

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1 Answer 1


Your air handler probably has insulation in it so it would be protected from the cold and the heat. It just moves air so clean filters are a must to extend the life of it. At first glance, insulating your duct work would be more beneficial than insulating the attic. This would make the hot air hotter in the winter and the cold air colder in the summer. Check to see if the sheet metal trunk lines have any insulation inside, I doubt they would.

Bottom line: air handlers don't need to be in an insulated attic.

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  • Thank you kindly! What do you mean by "air handler probably had insulation in it"? My duct work is already insulated, right? And what exactly are sheet metal trunk lines? If they don't have insulation inside, should I insulate them? Oct 9, 2023 at 14:17
  • @IMTheNachoMan The light grey panels that make up the air handler should have about 1/2" of fiberglass insulation glued to them on the inside. The round flexible branch ducks are insulated but the sheet metal trunk lines that feed them don't appear to be. The two boxes on the return air section that goes into the filter aren't insulated either. I would insulate them.
    – JACK
    Oct 9, 2023 at 16:05
  • Could I trouble you for drawing on the pictures so I can see what you mean? I could call someone but they charge $150 just to come the house and I'm really trying to save some $. If you can't, that's completely okay and I will do more research to figure it out. Thanks either way! Oct 10, 2023 at 1:17
  • @IMTheNachoMan This is the limit of my art work :-)
    – JACK
    Oct 10, 2023 at 2:56
  • AHs in uninsulated attics are common. Give the walls of the AH some taps. You may find that they're not plain sheet metal, but insulated. The round ducts appear insulated, but your "trunk line" may or may not be—give that the same taps. If it's not insulated, you should add some.
    – Huesmann
    Oct 10, 2023 at 13:39

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