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I noticed that the closet where my heating unit/AC fan lives is super cold. I measured the temp using a black and decker IR thermal leak detector and the temp in the closet is about the same temp as the air coming out of the vents. I'm guessing I have a leak but is this particularly bad, or relatively common? I have a super old AC (like 25yrs old). Above the heating unit is a lot of old looking fiber glass (with no lining), should I just remove all that, duct tape the crap out of it and re-insulate it with new fiberglass?

Matt
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  • Yes, yes and yes, except no duct tape; use mastic. See [my answer here](http://diy.stackexchange.com/questions/52501/is-there-any-way-to-stop-the-air-leak-through-my-furnace-without-compromising-it), but you've no need for a louver. – Mazura Jul 30 '15 at 02:19

1 Answers1

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There's a couple questions that have to be answered, before you'll know for sure if there's a problem or not.

First is if there's any combustion appliances in the closet (e.g. gas furnace)? If there are, they'll need to draw combustion air from somewhere.

Which leads to the second question, is there a duct to draw combustion air from the outside into the closet? Some furnaces draw air from the outside, but pull it directly into the combustion chamber. If this is the case in your situation, you don't have to worry about that. You'll only be concerned if there's a large open duct that leads to the attic, crawlspace, or outdoors.

If there are no combustion air ducts to the outside, then there's no problem with the air handler being in a conditioned closet. In fact, it's often recommended to install the HVAC system within the conditioned space.

In a lot of installations where the air handler is in the basement, you'll find a register within a few feet of the air handler. This conditions the basement, bringing the HVAC into conditioned space. Whereas when air handlers are in attics, they have to insulate the crap out of them. This is because the unit is in unconditioned space, so they use insulation to try and prevent the unconditioned air from interacting with the conditioned air.

tl;dr

  • If the closet is conditioned space, there may be no problem.
  • If the closet is not conditioned space, you'll want to seal up the ducts and insulate.

In either case, leaky ducts are not good. You'll want to seal them up with foil faced tape, and/or mastic.

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Tester101
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  • Thanks for the info. My unit (which has a gas furnace) appears to draw all of its air directly from 3 vents below the unit one near the stairs, one in a hallway and one from the kitchen (though it is strangely inside the pantry and the pantry door doesn't have a grate on it). My guess is this is a fairly standard installation for my area but the fact that the closet is so cold (while the Ac is going) seemed odd. The walls of the closet are finished but the ceiling is not, so you can see studs and insulation above the unit. I'll probably try some mastic and thermal tape to seal it up – Matt Aug 02 '15 at 06:53
  • (To seal up the leaks in the ducts not the ceiling) – Matt Aug 02 '15 at 06:54