My wife and I are looking at the cooling options for our new old house. Currently there is gas forced air but the upstairs is not well served - it only has two small ducts and no return on the upper floor, so one bedroom (and the bathroom) have no service.

We're looking at a mini split heat pump to heat and cool the floor, but have some issues:
1. Two of the bedrooms are very small - ~100 sqft with low ceilings. We're looking at the Mitsubishi systems, but the wall mounted units are 1/2 ton and we probably need 1/4 ton. Due to the low ceilings, I think it would blow right in your face. The low wall units are 3/4 ton - even bigger.

2. If we used one unit - maybe 3/4 ton - in the bigger room, I don't know how comfortable the floor would be without having heads in the other two bedrooms. We often close the doors at night and that has been a very bad setup in our current house.

Any thoughts on how comfortable either system (way too much or just one head but with doors in between) would be? Any thoughts on what else we might do? If it was just heating we could figure it out but we're pretty intent on well controlled cooling and I'm just not sure what we can do!

 

A single unit in one room would probably not be the ideal solution. One important thing you left out is your location. The heat load is an important consideration.

 

You could look at a Space Pak or Unico mini-duct system. The mini-ducts are a lot easier to route than full size so they work well in retro-fits with limited access. Tend to be pricey, but maybe not too bad since you likely only need a small unit to serve a few rooms.

 

I live in Seattle - a rather mild climate. I know that both contractors who have come out have done some sort of calculations, but for the part of the house where it feels like mini split systems are by far the most likely option, it feels like the biggest issue is finding gear *small* enough to serve each rooms - he noted that in the smaller rooms, we'd ideally have a head rated for ~ 1/4 ton, and I'm not sure if anyone makes gear optimized for that.

 

Mini split units usually have variable speed blowers and inverter compressors (which is also variable speed).

You don't have to run them in high speed.