Small House (12×16) Slab on Grade vs Crawlspace Foundation
I am designing an accessory unit that will be 12′ x 16′ and I had a friend recommend that I consider a crawlspace for the foundation instead of a slab on grade. My gut (and research) tells me that a slab with proper foam insulation detailing underneath would be more efficient to heat (cold, dry climate). As I discussed some of the mechanical details with him and mentioned electric tankless DHW (1 kitchen sink and 1 shower with not a huge risk for simultaneous use… it is a small space probably designed for 1-2 people), he said that a lot of local plumbers have found that the water temperatures are fairly low and folks aren’t that happy with them (I assume mostly bigger houses). If I did go with a “low boy” DHW tank, I think I would need a crawlspace for it so hence my initial inquiry. I am wondering if a carefully curated low-flow shower head and properly-sized Delta T electric tankless unit could allow me to use a slab on grade should I choose the slab on grade foundation. He makes a fairly compelling argument for the crawlspace as well based on ease of future changes and any plumbing maintenance issues as well.
I have attached a rendering of the space. It’s basically a unit I can live in while I build my main house.
Is something this small (and tight) a good candidate for a crawlspace if its mechanicals become too unwieldy to manage?
I’ve even considered the possibility of running a hot water line from the main house to the unit but that seems like a poor idea (distance could be 25′).
Thanks in advance for any thoughts folks have.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part