Mini-Split: Ducted/Ductless? Sizing? Location? (Manual J completed)
Seeking advice about mii-split sizing, type and placement. I’ve been reading on GBA about ducted mini-splits, but wonder if that’s the right solution for the new/remodeled house.
Here are the particulars …
* A gut remodel of a 1940s 1,200 sq ft bungalow with 7’ 7” ceilings in the PNW.
* As per attached floor plan, mostly open space but with a 14 x 14 bedroom extension. Just one person living there; thus doors will be open almost all of the time.
* A finished basement, but a 6k BTU Mitsubishi hyper-heat unit should work for that space (840 sq ft) + a floor heat mat in the bathroom.
* Manual J calculation gives a heating load of 8,850 BTU/Hr and a cooling load of 7,830 BTU/Hr for the main floor.
* Heat mats will be installed under the tile in the bathroom, in hallway between bed and bath, and in the kitchen floor space between the main cabinet wall and the island.
* Propane fireplace insert in the living room.
* Tight building envelope.
All this suggests that a 9kBTU mini-split should be sufficient for the main floor (Yes?), but would a single wall-mounted unit do the job? If so, where to put it? One option could be Point A on the plan, but the closet is in the way. It (the closet) supports a beam that replaces a wall we are removing so it cannot be moved. The next best spot might be Point B in the Dining/Sunroom.
Alternatively, would a ducted mini-split be better? That approach solves the code issue of not having a heating source in the bedroom, but those systems seem to start at 12k BTUs. Seems like overkill. Also, the only place to run the ducts would be in the unconditioned attic – though we could cover the unit and ducts with batts.
The HVAC contractor’s first bid was for a 24k BTU ducted system with 7 ceiling registers. The Manual J (that I paid for) has convinced him that we do not need that much. The HVAC company is a Diamond Mitsubishi contractor, so we’ll be using Mitsubishi equipment.
Thank you in advance for your advice and thoughts.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part