Heat pumps in a crawlspace or basement?
I am planning a home build with a detached garage. The house would be full ductless minisplits. The garage would have a conditioned office space in the ‘loft’ and heated floor out in the bays. We’re in the NE so we need to have footers that are 4′ below grade. I have been trying to figure out where to put heat pumps and then I had this idea. The garage footers need to be 4′ below grade. What if I maybe dropped that another foot or so and made a ‘mini’ basement(or would this be considered a crawlspace?) and put my heat pumps and manifold in there? The house is only 10′ – 15′ away. I can feed the house underground. This way all the equipment is protected and out of sight. I will need access. That could be on the interior to avoid having a bulkhead. Do I need to consider circulation? Do I need a slab or just gravel and pads for the equipment? What else do I need to think about for an install like this?
Note: We are looking at using something like Lite-Deck for the first floor of the house. This an insulated flooring system. Possibly usable in the garage although I would need to look at what kind of weight can be used. I imagine it could be made stiff enough since the technology was designed for commercial buildings.
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I love this question since I'm wondering the same thing about my upcoming remodel. My climate zone is 4b. Sacramento Valley, to be specific. Eager to see the replies for your post.
So you propose to dump the heat that gets removed from the house into the crawl space? What will happen to the temperature of that space after a prolonged hot spell? I suspect it'll really be impinging on the efficiency of your heat pumps.
Personally I wouldn't do it.
Good feedback. I do wonder what the impact would be. The garage is pretty large. I believe the most recent dimensions are 24x38. I can see it would be beneficial in the winter where the air is more temperate compared to being directly outside. In the summer is a different story but maybe not so bad. We're in zone 5 (although it's been feeling like 6-7). Perhaps if the basement were vented. Then again, we would have the heat pump for the water in there so while cooling the house would be pumping heat out some would be pulled back in for hot water.
You would need venting for your space, with an air flow greater than the air flow of all your heat pumps added together. So plan for large capacity fans.
You can run some numbers of how many BTUs you would dump into the space, and see how many cfm you need for a set of expected temperatures.
The extra cost of the ducts and fans (and the operating cost) would negate some of the advantages of the mini-splits.
Suppose these weren't mini splits, but a central unit with the air handler in the crawl space. Would you put the condenser in the space with the air handler. No you wouldn't.
That sounds like a great way to hide your equipment, but there are a few things you should consider before going forward. First, the circulation issue—since this will be an enclosed area, you’ll want to make sure there’s enough airflow to prevent moisture buildup or heat buildup from the equipment,Or consider portable AC