Help! Replacing heater duct under floor

[Ozzmosis]

Hello!

2003 Wildwood T23BH travel trailer. Duct in the floor requires replacement. This spring i found that mice got into the trailer over the winter and made a mess. Bleached everything etc... Found the mice were in the floor duct. Well, the floor duct never moved air properly anyway, so today I removed the fresh water tank, and cut open the tarp-type stuff for the underbelly. The duct is made of foil backed fiberglass insulation. Fiberglass is on the inside of the duct making it impossible to properly clean it. So I pulled it all out and tossed the mess in the garbage. Found the mice got into the tarp-like underbelly and found the duct, where they chewed thru the foil and made a nest in the rear of the duct.

My problem is, what to use a suitable duct material? There are a couple of frame crossmembers that I have to cross over, and the height between the crossmember and the underside of the plywood floor appears to be about 2-3/4" I could use the aluminum dryer duct and crush it to fit, but i'm not sure about insulation. Do I crush the duct and use spray foam to insulate? do i use duct that comes with insulation? Do I try and fabricate a new duct with sheet metal and glue fiberglass to the underside? Pics are attached for clarity.

Thanks for any input!

Overall Pic

Plenum under furnace

Front Register

Middle Register

Rear Register

Crossmember to floor clearance

[Iwannacamp]

Imo. You have a few options. The best isn’t the cheapest. Call/google/ask around for someone who does sheet metal work. They will have or can build metal duct insulated on the inside and you put together and install.

The next option is cheaper. Get some duct board from an HVAC wholesaler. They should sell it to you...most of the time if you pretend you know what you are doing. I think it’s about $30 a sheet 5 x 10 feet I think. Downside is you really need a duct kerfing tool like this

To cut the kerf out so you can fold it. You can do it with a box knife, a 1x4 straight edge, some patience and practice. It ain’t rocket science. The measuring is the hardest part starting out. The duct board around here is 1” or thicker so it will use some of your space. Duct board tape(not duct tape) and some patience. I haven’t tried, but I am sure there are boocoo YouTube videos about it.

I will help if I can on info.