Insulated mobile home Skirting Question

[ideallysleary]

Last year, we had one brand new home with new slab and insulated skirting. It was the only home in the park that had the sewer line freeze. The outside ambient temperature was 8* and it was 10* under the home. Guess what, the slab was freezing cold. In fact, we had old homes on dirt and regular skirting which were above 32*.