Heater exhaust

[BlueBliss]

We just reloaded a hot water machine into a cargo van. We re-attached the old duct work that we used for the last machine in this van. The duct is just air-conditioning ducts from a home store, wrapped in insulation. It's not a great fit and leaks....
Long story short, I'm curious if anyone is using any great materials for exhaust?!
There is only about 5 inches between the heater and the van roof. We don't want to go through the roof because we have a ladder rack/work platform on top.
Any suggestions?

 

[scottwash]

a trailer

 

[Kiloman]

Go to your local heating and air place an have them fabricate an exhast they usually will do it out of stainless steel looks good and lasts.