Huntindog wrote:
I did similar to what Larry did. I took a different tact on the insulation. I used a 1" thick hard insulation (I don't remember the name, but Home Depot has it) rated @ R7. It went directly above the coroplast reflectix and on the insides of the framerails. Basically I built a cooler inder the TT floor. Then I enlarged and added another heat vent. I used heat tape and insulation on all water lines. It really didn't cost all that much, but it was a labor intensive, but fun project. It should be good to 40 below now. I haven't had the opportunity to test it though.. I am SURE that it is much improved over stock.
I believe that enclosed is a worthwhile option. It offers some benefit and can be used as a base for upgrades if desired.
Actually, I did all that work in that album back in early 2009 before I think you even had your current trailer and did my insulation very similiar to what you did, but I did not put any under any of my tanks since there wasn't enough space under them and I wanted as much warm air as there was from the ducts to circulate around them.
Here is a pic of the insulation at the rear of my trailer where the holding tanks end and it just lays on the underbelly supports from frame rail to frame rail and is not even taped together so I could slide it in/out in sections. I estimated I insulated approx close to 80% of the underbelly area this way.

Larry