How to enclose bottom of RV (with slides) for winter?

Hi Gail! There are insulated vinyl panels. That's what we used. It's amazing stuff! It's called Rapid Wall. It was very easy to work with.

Cheapest and warmest are definitely the straw bales great insulation I have 38' Monaco with slide & that's what I use you when we stay up in mountains by Flagstaff. You can even cover them with black landscape plastic(comes in rolls) so they stay dry and the black will absorb even more heat from daytime sun.RV's have lousy insulation.Should check into mouse proofing it too depending where it's gonna be parked. They want to be warm & cozy too you can get cheap live traps at hardware store and use spray foam can to seal around any incoming pipes,hoses and electric.

That looks much better than the hay or straw bales, the bales tend to draw mice.

Not trying to be mean but, do you want to look good & be cold or be warm & toasty? Straw bales will also keep it cooler in hot Texas summers,you could do both straw and nice skirting but it'll be more expensive. With a Trailer or RV the costs are always an issue especially if you don't have much money or are trying to live in one to live a cheaper/lower cost life(no home owners expenses) because you'll have extra expenses like gas,diesel fuel,engines,tires,brakes & more. The mice and ants will come in even with out the straw bales they climb in/up the tires,water lines,electric & sewer pipes. DBL stick gorilla tape helps with this put it just outside R where lines come in & then again where lines come into RV inside compartments. Make sure you don't block any exhaust pipes for engine,propane or generator.You don't get real cold where you are but you'll need to insulate outside lines water & sewer so they don't freeze. Also don't block or seal roof vents you'll want those to make sure you can still vent inside to prevent any moisture build up that will increase chances of getting mold. Especially around area you are in with the high humidity. I have also have installed 3 different detectors in mine carbon monoxide,propane,and fire. Getting started can be daunting but after you get the hang of all this it'll be fun.Most RVer's are couples however I'm single women in 60's and if I can learn all about this you can too. https://traveltips.usatoday.com/travel-trailers-can-use-winter-61215.html https://rvinspiration.com/rv-life/cheap-diy-rv-skirting/ https://www.google.com/search?q=Best+tips+for+living+in+RV%2FTrailer%2F+full+time&rlz=1C1CHBF_enUS750US750&oq=Best+tips+for+living+in+RV%2FTrailer%2F+full+time&aqs=chrome..69i57.26528j0j7&sourceid=chrome&ie=UTF-8 https://www.google.com/search?q=full+time+RV+hacks&rlz=1C1CHBF_enUS750US750&oq=full+time+RV+hacks&aqs=chrome..69i57.8900j1j7&sourceid=chrome&ie=UTF-8

Thank you for all the tips. I can use them.