This weekend we're installing insulation in our attic. I've gotten everything ready except for my air handler for heating and cooling, which is located in the attic. I've got 30 bales of fiberglass insulation which will be blown into my attic.

Should I construct a plywood wall around the air handler to prevent the insulation from getting close to it? Should I just create a slope so that there is little to no insulation near the air handler? Or can I just blow the insulation right up under and around the air handler as if it wasn't even there? For reference, we're shooting for about an R-40 value, which is approximately 16" of insulation.

  • By "air handler" , do you mean your HVAC unit? And is said handler on a platform?
    – Machavity
    Commented Dec 30, 2016 at 17:11
  • @Machavity, by "air handler" I mean a unit I have in my attic. It's got ducts going into the ceilings of my second floor rooms. There is a pipe/cable/tube coming up from outside that is connected to a heat pump for cooling. And the unit is also my heating unit via electric heating (my heat pump outside is only for cooling, this electric heating is not emergency heat). I'm not 100% if it's on a platform (not at home to go look), but I believe it is on a platform with a tray under it for condensation, I assume. Commented Dec 30, 2016 at 18:42

2 Answers 2


Contact with insulation will not directly harm your air handler. However, there are a couple of reasons you should try to keep the insulation away from the air handler:

  1. Insulation under the air handler could be a problem if you ever have a condensate leak.
  2. You should be able to access the air handler for any future maintenance or repairs.

Condensate drainage: when used for cooling or dehumidification, your air handler will collect moisture from the air that flows through it. For attic units, this is usually drained through a small PVC pipe to the outside of your house. If this drainage pipe ever develops a clog, the condensate water can back up and leak from your air handler. Because of this, air handlers installed above living space should have a drip tray underneath, along with a safety float switch. Should your air handler develop a condensate leak, the water will leak into the tray (instead of down into your ceiling), and the float switch will detect the pooling water and shut off the cooling. This gives you a reason to go inspect the air handler, so you can detect and fix the condensate clog before it leaks down into your ceiling and causes other damage.

If you place insulation under your air handler, it would interfere with the flow of any future leaks into your drip tray. The blown insulation could soak up the water itself, channel the water off the tray, or physically interfere with the normal operation of the float switch. Depending on the plumbing layout, it could also be carried into the condensate drain piping and cause a clog. For all those reasons you'll want to keep the underside of the air handler clear. And if you don't already have a drip tray with float switch, consider getting one -- way cheaper than cleaning up from a major leak.

Example of air handler with drip tray

Maintenance access: you may need to access your air handler for maintenance, such as filter changes (though your filter might be somewhere else, such as on the return air grille) as well as occasional repairs. Make sure you can still navigate around any insulation to access the air handler, and that any access panels on the air handler can still be opened.

So: don't surround the air handler with insulation. If you can simply avoid that area when blowing insulation, and you're maintaining access, that's probably good enough. For bonus points, build an enclosure out of rigid foam boards around the air handler. That will not only protect it from the blown insulation, but provide some extra reduction of any heat loss or air leakage. The foam boards can act as wall board with minimal structure, but make sure you have a simple way to open the enclosure if needed.


I don't think you'll blow it directly at your HVAC. I've not blown in myself, but I did pay a guy and he blew in extra around it. He then raked back around the HVAC. I think you'll have to rake areas you can't blow directly onto.

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