Check the R factor of wall insulation. Doubt if they're ANYWHERE NEAR what any good four season RV has. Also check ceiling R factor. Most anything ELSE can be added but those issues are not easily changed.
2011 F-150 HD Ecoboost 3.5 V6. 2550 payload, 17,100 GCVWR -
2004 F-150 HD (Traded after 80,000 towing miles)
2007 Rockwood 8314SS 34' travel trailer
US Govt survey shows three out of four people make up 75% of the total population