I am planning on building a 16x20 cabin with a loft. This off-grid cabin (no power/water) is only for a weekend/family get-away (for the wife), and my hunting cabin with the grand kids (not sit around and entertain folks). I have been researching the need to insulate a floor or not. Many videos on youtube talk about cabins in Alaska or Michigan and I get it to insulate there. But does a cabin in AL need insulation on the floor? (forget the extremes of the single digits the last two years, just normal temps of 20+). I have a slight slope, so there will be some open air underneath. I can always enclose the underpinning to trap heat, or apply some ventilation. But should I install 1x2's on the bottom of the joist, lay plywood on the 1x2's, and then lay insulation batts underneath the 3/4" tongue and groove plywood? I am concerned about proper ventilation, not trapping condensation which leads to mold, and of course the wife complaining of critters getting through! lol. I plan on installing a wood-burning pot-belly stove to keep the chill out. I will probably install wall insulation and maybe overhead. Thank you.

I believe I'd stick with just insulation overhead and walls. I'd underpin / seal it good and add a couple of closeable vents. Leave the insulation off under the floor.

This.

That's what I was leaning to. Condensation is a tricky thing. I've seen an empty enclosed plastic tub covered by a tarp in the back of a vehicle get filled with gallons of water.

Insulation under a crawl space down here in the humid South never has worked out well. Not really needed any way, this far South. It's cool in the Summer and warm in the Winter in the crawl space .

I had a floor man tell me not to insulate the floor of a 16x40 cabin I was building for a hunting camp. He said the floor would sweat and eventually cause rot.

My father was a residential contractor who built high end houses. He refused to insulate under a house. When the city started requiring it , he along with a couple more contractors would insulate them and after final inspection they'd go back in and rip it out. It took a few years for them to figure it out, but cities stopped requiring it when they figured out it was causing mold and rot.

Sold! Thank you.

Post up some plans, I’ve been looking this week at lean-to cabins. I just think it’ll be easier to do it myself as a lean-to. I’m gonna build one at my 3 acre lake someday.

I would suggest a sink, propane wall heater, and wire for electric. You can use a solar generator like a Bluetti or Exoflow to power it and solar panels to keep it charged up. Not having water requires you to figure out the bathroom situation. Our cabin is roughly the same size and over the years we have added all of the above. We do have water so that is a bonus. We ran our own waterline over a mile of pipe but it’s worth it. We poured a slab to build on.

Even though it's a little cabin , put down a good moisture barrier ground cover under it.

Skip the insulation underneath. If you underpin it then add a ground vapor barrier and adequate ventilation. The only crawlspace insulation that actually works long-term is spray foam and even then there are a list of do's and don'ts as far as best practices.

My son has a 20x40 cabin sitting on a edge of a hilll. About 5 feet off the ground in the front yard and 8 feet in the rear. Lot of storage underneath. Solar with a gen. gas for water heater and gas stove. wood heater catches water from the roof and runs it through a filter. Started in 2015, still working on it.

^^This^^ Can't imagine the wife and/or grandkids wanting to getaway to the cabin if they have to use an outhouse. Maybe you're lucky like that but my wimmins would never leave the driveway without a working shower and toilet.

Forget women. I don’t know many guys that would put up with that.

My hunting cabin is a few feet off ground. I had it spray foamed walls, ceiling, and floor with closed cell foam. I can heat with pot belly stove and cool with one single wall air conditioner.
Cabin is 40x30x14 high.
This was 12 years a go and I would do it again.

This is kind of the type I'm planning: Cabin Except I'm not doing a bathroom, and I plan on doing a front porch.