Hi Dax Foam in a can would be a very expensive option. I guess you have a damp proof membrane below the slab? its amazing how many attached slabs compromise the house dampproof course :) Insulating the slab isn`t too difficult. Use closed cell rigid foam boards 1"-2" thick, no need to go thicker than 2".. the law of diminishing returns becomes a factor. You can install the rigid insulation board vertically ~2ft deep or horozontally (aka "wing" insulation), at least 2ft wide with a gentle slope away from the slab. Don`t forget about drainage. Don`t worry too much about insulating underneath the slab (unless using underfloor heating) Heat always moves to cold, cold doesn`t move. The deeper the soil below the slab..the warmer it is. The temperature differential eventually reduces to zero and all downward heat movement stops. On the other hand, at the edges of an uninsulated concrete slab you find pretty huge temperature differentials driving the heatloss for the full length of the perimeter, which is about 44ft for an HF 12x10. Hi Sheri, If the slab length extends well beyond the greenhouse length in one direction, theres not much you can do in that direction unless you can create a gap..not easy to do :) Insulate the perimeter of the extra 2ft width and around the slab in proximity of the gh where you can, in this case maybe only 3 sides. It won`t be cost effective to insulate the entire slab perimeter if the gh is located at one end.. the exposed top surface of the concrete will be responsible for most of the heatloss. Horizontal insulation over the concrete is an option, but again probably not worth the expense. Doing what is practically possible without going overboard is usually the best plan, insulation investment vs return :)

I have made hypertufa stepping stones or tiles that have held up using a greater proportion of cement to aggregate. I would make the mix probably at least half cement. It will be heavier, but that is a good thing for pavers or tile. If you want the floor to be a little more porous, rougher, and more like stone, hypertufa could be the way to go. It will also grow a little moss on it, if that's something you may like. Something else I have done to make a walkway--use one of those plastic molds from a big box home store and use concrete aggregate mix. This goes pretty fast. Each mold takes one bag of concrete, and about the time you are ready to remove the mold, you can have another bag of concrete mixed and ready to pour the next piece.

Eight years ago, I put an 8x12 GH on an old deck floored with treated 2x4. Covered the GH floor with boat carpet from Lowes. I figured anything that will hold up exposed to the weather on a boat will do OK in a GH. Went on easy. Rolled it out, trimmed the edges, and battened it down along the edges with treated 2x2. Nothing else holding it down, and it's never bunched up, pulled loose or anything. It shows no wear that I can see. When I give it it's annual vacuuming and shampoo in the fall it looks like it did when I laid it. Water goes right through, but bugs, spilled soil, debris etc. are shut out both ways. Pics when new:

I have heavy clay soil. Zone 7b North Alabama. I put the paver sand down and compacted, then put the pavers on top of that. I think I could of just skipped the sand. https://www.lowes.com/pd/American-Countryside-0-5-cu-ft-Tan-Paver-Base-Sand/50408222 They also make a rock base. https://www.lowes.com/pd/American-Countryside-0-5-cu-ft-Paver-Base/50408224 If you scroll down a little, you can see a picture of how to lay out a paver patio. I did not need anything that solid. I just wanted an easy to walk on floor and no mud. https://www.lowes.com/c/Pavers-retaining-walls-Outdoors If you want rock for drainage, I would think almost anything you could use in a driveway would be fine. They have the same stuff at Home Depot also, You might want to try a few down the middle without anything and see how they do when it rains. Like I said, I wasn't building a patio, so I did cut out quite a few steps that would be needed for one. They have stayed in place for 10 years now. The only thing I wish I had done different is to not have the gap between the paver. It is sized, nominal 12" x 12", is really 11.75" x 11.75", so you can put the small pebbles, groundcover, or polymetric sand for a patio.