Mini split retrofit w/ manual air seal & cellulose…. or spray foam encapsulate? – GreenBuildingAdvisor

Generally speaking I have two options. Currently the upstairs HVAC in the unconditioned attic is exposed and leaky, and very inefficient and causes passive and active air leak.

I think I’ve narrowed it to two options- the “easiest” is to keep it as-is, and have the rafter level sprayed with open cell (maintain baffles to ridge vent), and apply DC-315 thermal barrier coating. This would be 7″ on top of baffles for R25 (with thermal break overlap on rafter butts). I would remove the FG in the joist bays. Total cost, around 5800 before any tax credits. The HVAC is 7 years old, SEER 13, and I see the replacement looming on the horizon. I hate it in the winter, but much of it’s ineffectiveness is due to the poorly designed and executed attic. That cost would be additional in the next 5 years or so I expect.

Second option, I think is better but much more labor intensive, would be to install ductless mini splits with a zone for each room (likely two 3-zone units due to lineset lengths). The linesets and potentially some condensate lines would have to run in the attic. I would then remove all existing FG, block rafter bays around baffles, air seal the attic plate, build any “doghouses” around lights and ceiling cassettes, and then apply R60 cellulose over the attic. Total cost would approximate ~10,000 with a fudge factor applied and before any tax credits (to the best of my coarse estimating).

Personally, I love the idea of mini splits. I’m capable of installing them myself, but have quite a bit of homework in front of me.

What would you do?