I lived in my fifth wheel in Michigan then Ohio for four winters. Right before winter set in, I contacted a boat upholstery shop and he was going to make a custom fit skirt for my RV using Sunbrella fabric in my own color. He was going to sew in a pouch on the bottom so I could slide a 2x4 or some heavy item to keep the fabric down on the ground. He was going to mount a track system on my RV and the mating track sewn onto the fabric. It would be made in sections with those big plastic boat zippers to hold it all together. I had a thirty nine foot fiver and back in 2008 he quoted me $2,500. He was about to start the project and a bad cold front blew in and it stayed below freezing after that. His shop wasn't heated and it was to cold to work with the material so he didn't make it.
That left me in a bind so I ended up buying 1/2" extruded foam board (NOT the white bead foam board) in 4x8 sheets, some 2x4's, long nails (8 or 10" I think), roofing nails with those big plastic heads, some silver aluminum tape and a couple pieces of corner wall edging. It's basically a piece of angle iron made out of clear plastic.
I nailed the 2x4's to the ground all the way around the RV, then cut the foam board and taped it to the RV and used those roofing nails to nail it to the 2x4's. I usually ran at least a double layer of tape and triple in areas that might be weak in strong wind. On the back of the coach on the corners I taped those up real good but on the front over hang I used those plastic angle pieces to make the joint strong taping both the outside and inside seam. I even cut out a small door so I could store stuff in there. I would cut out a small door you can put a heat in if you ever have a freeze that will be done.
I experienced temperatures as low as -20 at night and it was hard but I made it. The one thing I highly recommend is to buy a couple of those Mr Buddy heaters and keep a case of one pound bottles on hand. I lost power plenty of times and my electric heat wouldn't work and my propane heat will only work until the battery goes dead. Yes you can use the stove for heat but you might run out of gas as well. When it's cold you will appreciate the little portable heaters. Yes I know its dangerous but when I flew back to Michigan and I had no power that was the best I could do in -20 temps so make sure your CO detector is working.