I am talking about the inside of the register boots

I have installed three new register boots, all of which had one inch of fiberglass insulation on the sides and top of the inside. Sadly though, the insulation in the third one got torn up from an issue involving a screw (got all mangled by the screw).

My question is, does it really matter if it’s insulated on the inside?

Relevant detail: these are installed in ceiling, and I just had attic reinsulated to R38. I’m just trying to make sure I never have to worry about condensation and such.

  • If the old ones did not I would not worry about it. Why were they replaced?
    – Gil
    Jul 25, 2021 at 22:22
  • The old ones are the old circle style registers. I replaced them for rectangular style ones.
    – CamParker
    Jul 25, 2021 at 22:39
  • Were the old ones insulated?
    – Gil
    Jul 25, 2021 at 22:46
  • No they were not.
    – CamParker
    Jul 26, 2021 at 3:11
  • You might want to check the others they may have the same problem. At least tape the joints with duct tape, and prevent air leaks. That should should suffice because of the insulation they are in but insulation never hurts and is not that expensive.
    – Gil
    Jul 26, 2021 at 16:31

1 Answer 1


Yes, it matters as you have air leaks. You also need to chalk all the boots if it was not done. It is about 20-25% of AC or Heat leaks when the boots are not chalked& The joints have to be mastic to the trunk line and all things need to be foil taped or your throwing $$$ out the door. I have brought my energy usage down over $150-225 a month doing a variety of energy saver things. But none as big as sealing up trunk, boots and runs!

  • What is chalking the boots? Are you talking about mastic?
    – CamParker
    Jul 27, 2021 at 12:12

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