Heated enclosed basements require far less energy to keep the tanks warm. Our rig has single pane windows but we section off the cab and have fitted reflectix panels for all windows that we keep in a roll under the bed. Have only dry camped to 20F with 20 MPH wind with no issues. Went colder on electricity and added a 100W clip lamp to enclosed wet bay which kept things warm.
Here is a current ad for a 2011 28 foot Triple E Regency 28GT which is the non-cabover version of what we were looking for. $73K:
https://www.rvtrader.com/listing/2011-Triple-E-REGENCY-28GT-5000724336Similar layout to our dual-slide Jayco without the cab-over.
