Mini split system with unvented attic and crawlspace
michaelrader
| Posted in General Discussion on
I am building a home and trying to decide on an HVAC system. I’m tempted to go mini-split for the savings but is there anything I should consider with having a conditioned attic and crawlspace? Will I need to insulate ceiling joists if I go mini split? trying to wrap my head around this setup.
Replies
I would start by getting your hands on some manual J software, and punch in the details of your house. Include the attic and crawl space in the conditioned areas if that is your plan. If you plan to condition them, they should be figured in like any other room, but one without windows, (and different exterior heat gain/loss surfaces)
remember you likely need to heat as well as air condition. (depending where you are, of course)
I want to guess that you would need more than one mini split, depending on the size of the house. how many is a question.
I did this 11 years ago, looking at new HVAC equipment, and priced out everything from cheapest you can get, to $12k worth of wells to feed a geothermal system.. purchase price and ten years of operating costs.
You can also do what-ifs on better/more insulation and other details, and inform design choices.
decisions to skip ductwork might be worth while, depending on where you are.
If you have a conditioned attic you wouldn't need to insulate the ceiling joists. Talk to a reliable HVAC contractor (Minisplits aren't a DIY thing) and have them work with you on design. It depends on the house. I've seen high-performance houses in Zone 5 get by with two or even one head.