Sizing a ductless minisplit for heating
I’m going to install a ductless heat pump. I settled on LG Art Cool Premier (HYV1 or HYV2). Now I need to figure out system size, and there is too much info.
I have 550 sf addition built in late ’80s, which is a split lever open space, and is VERY cold (i’ve attached some photos)!
It has a large french door (8×10′ glass, 3 sections), 7 windows, and 5 skylights. All are double glass.
The whole addition sits over VENTED crawl space/foundation (it has 2 vent openings in the concrete!!!). Second level sits over a garage, and a lot of cold air comes from there (will improve insulation).
Insulation is questionable, but it’s always cold there. Drafts from unknown sources (either roof venting, or garage or foundation or poor insulation or too many windows.
The main house heating system is ducted force hot air (gas), very old, and wasn’t designed with addition in mind. Addition feeds off the main floor and basement duct. So needless to say, there’s not enough hot air coming in. However, it still helps.
Ok, so I calculated on ecomfort the heating capacity to be 17000 btu/h
The 12K LG (LA120HYV1) has 13,720 btu/h at 5F (4.68 COP)
The 18K LG (LA180HYV1) has 19,300 btu/h at 5F (3.81 COP)
THe 15K newer LA150HYV2 has 18,490 btu/h at 5F (3.81 COP)
This article on GBA ( https://www.greenbuildingadvisor.com/articles/dept/musings/ductless-minisplits-may-not-be-efficient-we-thought ) says I should not oversize…
PLEASE PLEASE help me with your thoughts and advise.
PS – I know I MUST improved insulation … it just takes time 🙁
I also have a vented attic space adjacent to 2nd level, with outside temp air, separated from living space by an interior door … I’m thinking about closing the vents in the winter. (i’m a roofer, and can figure this one out).
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