It is not difficult to lag your aquaroll, lift it off the floor, or even keep it inside until needed, I've seen all these things done......
However .. many, many folks forget that waste water freezes just as easily, and many waste pipes have long lengths under the van totally unprotected.
I have helped too many folks you have plenty of clean water .. but sinks/shower trays full of the dirty stuff going nowhere.
So think about waste as well as clean. In REALLY cold weather (-18) we don't use the onboard stuff at all. containers of fresh water indoors, kettle to heat, bucket or bowl used instaed of sink, that way it can be carried out and got rid of.
A "strip wash" is as hygenic as a shower, just takes longer