Which type of mini-split is best for my situation?


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Old 01-10-16, 12:37 AM
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Which type of mini-split is best for my situation?

We are renovating the 3rd floor of our 1902 home to be a master bedroom suite with large walk-in closet, full bath and a bedroom. Due to the complex framing of steep hip roof, 6 hipped roof dormers and no ridge or soffit vents on 3 sides of house we decided to convert it to an unvented space. We had spray foam applied under the roof deck filling the entire depth of rafters from ridge to eave. There will be ceiling joists, creating a 5' flat ceiling at 10' from floor (leaving small "attic space" 5' from new ceiling joists to ridge). The total square footage of the 3rd floor is 850 sq ft.

I got quotes from 5 different companies for installation of mini split system to heat and cool the space and each had slightly different approaches... these are the 3 main "ideas"

1- a standard 24,000 btu system with wall mount unit, to be mounted on interior wall that divides closet and bathroom

2.ducted mini split in attic space with vents in bathroom, closet and bedroom wall or ceiling (also 24000 btu)

3. 2 zone system with wall mounted units in both bedroom and bathroom - this company calculated 18000 btu

**note - the closet entry from bedroom will only have an opening, no door to be installed
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My question is- how well would a single unit on bedroom wall cool the entire space? Heat is not an issue... it is currently below 20 degrees here and attic is comfortable with no heating system after having spray foam installed.

The ducted system is almost 2x the price and the 2 zone ductless is about 33% more than the single.

Thoughts? Anyone with experience with these systems in similar situation?

Thanks in advance.
 
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Old 01-10-16, 06:56 AM
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I'm not an HVAC pro by any means. You've got a fairly narrow and long space that is broken up with a lot of walls and partitions. I don't think you will be happy with performance of the single head unit. You've gone to a lot of cost and effort to create a nice space, you want it to be comfortable in the summer. I think the ducted system will give you the best temperature balance and comfort. 2 zone is next and probably pretty close to the ducted. Bathrooms can be challenging because of the humidity and it's nice to have separate control. And it's probably not that important that closet be well regulated. Single zone a distant 3rd.

If the access to the attic mounted unit will be difficult or cramped, then that would be another point in favor of the 2-zone solution over the attic system.
 
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Old 01-10-16, 06:44 PM
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Good Point

Thanks for the response, the attic access is something I hadnt even considered. I appreciate your input!
 
 

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