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Ceiling Cassettes in Drywall (into unvented attic) Questions

Hi Folks! Updating our mechanical systems a little at a time (I'm here because hydronic heat is our primary heat source) and in order to preserve the room-by-room temperature control we love with the heating and avoid ducting a previously unducted home, we've gone with mini splits for cooling. (We did go for hyper heat units to maximize our cost savings potential in the shoulder months but I'll never give up radiant heat due to comfort)

With that said, wall mount units were out of the question for the wife, who originally wanted ducted mini-split heads for each room. We landed somewhere in the middle with ceiling cassettes and are happy with how they look, and I am happy with the lack of a squirrel cage fan.

The questions start popping up when we get to insulating and winter with these units. The manufacturer's documentation is mainly centered around these in drop ceiling situations (aka they are entirely in conditioned space). This is not the case for our install. My plan is to use rigid foam to box the units themselves in like I used to non-IC rated can lights to try to get both some form of air seal and something I can surround with the blown in insulation we have in the attic. Any options I'm missing there?

The next conundrum is the condensate lines. They use built-in pumps (bleah) and pump them up 20 inches and it's all gravity drained through an interior wall to the basement. Do I need to insulate the entire condensate run? Obviously there will be a little water left in the pan when we switch from cooling to heating, do I just not worry about that since the unit will be "well enough" insulated to keep it from freezing?

I've reached out to the manufacturer as well, but I thought some of you might have some great real-world experience to draw on.


  • pecmsg
    pecmsg Member Posts: 4,388
    edited May 18
    There's a slight possibility of condensate forming during defrost.

    Where is the pump discharging to?
  • iced98lx
    iced98lx Member Posts: 61
    The pump is discharging into lines within the attic that then run down an interior wall to a conditioned space and into a trap, then the sewer system. Sounds like I should plan to insulate the condensate lines if I want to use the system for heat in sub-freezing weather...
  • yellowdog
    yellowdog Member Posts: 91
    no need to insulate the condensate lines in the attic. just put the insulation over the unit itself and you will be fine.