My experience with trying plastic shrink film, bubble wrap, plexiglass, and clear vinyl attached with Velcro to protect against heat loss in cold weather.
Winter
How We Made $200 DIY Vinyl RV Skirting for Winter
After pricing professional RV skirting, we decided to make homemade skirting to prepare our fifth wheel RV trailer for a winter spent in cold weather, which only cost us around $200.