Confused and worried about minisplit sizing
We’re building a house in Toronto, two stories (both about 1500 sqft each), first floor R26, second floor R32, second floor ceiling R70, with HRV, de-humidifying system, window-to-wall ratio 12%, windows mostly face east and west, windows are Fibertec high-efficiency, fiberglass frame, low e-coating. Whole house will have hydronic floors for heating. We’re planning Mitsubishi mini-splits for A/C, but we’re very confused about sizing and placing of heads (and outdoor units).
The HVAC load calculations say we need sensible cooling of 27300 BTU and latent cooling of 11700 (total 39000). This seems a little high to us, though still plausible. What’s the best layout and sizing of the minisplit heads? We have three bedrooms upstairs (each with ensuite bath). Main floor has great room (kitchen plus living), separate dining room, and library. Current HVAC design has second floor with three 9000 heads, one in each bedroom; main floor with two heads, 9000 in the great room and another 9000 in the library.
We’re worried this is oversized given our semi-tight envelope. Will the 9000 heads in each bedroom be too cold? Conversely, would a single bigger head in the upstairs hallway not provide enough coolness for bedrooms with doors closed at night? There seems to be a lot of advice out there that fewer bigger heads is more efficient than more but smaller heads. But wouldn’t the latter give us more control? This question seems particularly pressing for the second floor, which is not open-concept at all, and where rooms will generally have closed doors when they’re actually inhabited.
Any expert help and advice will be greatly appreciated. This is all new for us and this website has already helped us a lot.
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