A couple of ideas that may settle some of the arguments against sand. yes sand has very little insulating qualities by its self, BUT if you insulate under it there would be no reason not to use it. if you have an elevated floor that does not contact the ground then yes if its wet it will freeze solid like a brick. if its clean and dry it will stay loose and the air spaces between the sand grains are the tiny bit of insulating effect it has. if you use a 1" Extruded Foam board under it you will gain an R factor of 5. plus sand & plywood you would have about an R8 total.
If you have a sand layer on the ground its going to draw up moisture. inside a building its like a green house and the sand will radiate water upwards into a warm space. if the ground freezes and there is no thermal break then it will freeze the sand solid. SO that being said you need to create a thermal break if using sand in winter. I suggest using a layer of course gravel, pee stone or rock. then by putting a landscape fabric over that then sand it will create an air space big enough that it should breath and stay dry and out of contact with the ground.
If you have a sand layer on the ground its going to draw up moisture. inside a building its like a green house and the sand will radiate water upwards into a warm space. if the ground freezes and there is no thermal break then it will freeze the sand solid. SO that being said you need to create a thermal break if using sand in winter. I suggest using a layer of course gravel, pee stone or rock. then by putting a landscape fabric over that then sand it will create an air space big enough that it should breath and stay dry and out of contact with the ground.