Hi All. Even in this bitter cold (10 degrees overnight), our Mitsubishi Hyper Heat unit on the 2^nd floor is blowing noticeably warm air via the 4 supply registers. But the first-floor units are barely blowing at room temperature.

Our 100-year-old house is 1450 sq ft, 2 floors, basement and attic is in southern Westchester County, zone 4A. The attic is fully insulated with close cell foam on roof deck and gable walls to R30+, but the rest of the house is only R7 at best.

Our first-floor system is a MXZ-3C24NAHZ (24k btu) outside running two MFZ-KJ09NA (floor standing units) on the 1st floor, and MSZ-FH06NA wall model in the basement. Our 2^nd floor is a SUZ-KA18NAHZ (18k btu) running a PEAD-A18AA in our conditioned attic feeding 4 supply vents with 5 returns (one over the stairwell)

The basement is an earthen floor. It’s hovering around 40-45 degrees regardless of the outside temps. We’ll be installing a new 4” slab with 2” XPS for insulation (if the weather cooperates!) and the basement walls with 2” of closed-cell – and I’m sure that is going to make a huge difference.

But I think that the current situation has exposed a design or installation flaw and wanted to get your views.

The 1st-floor units are installed directly against the plaster walls and are sitting directly on the wood floor. Would it have been better to stand them off of the walls and floor – a thermal break of sorts? 

The impact of the floors will be reduced greatly when the basement is insulted and the sill and band joist is foamed, but the walls will continue to be an issue for some time while we get our next steps lined up for the remaining above grade insulation.

I have included a PDF with thermal images of each unit and the temps on and surrounding them. The difference in temperature between the two floors is 10-20 degrees and it’s a major buzz kill (although no burst pipes yet) Seems like we could do better?