I have an old, old Vastex Econored
Attached is the shroud (basically an upside down box) I built just using A/C 1 inch insulation backing (foil on 1 side) board and their silver backed tape and a tub of the goop that hardens when dry. All from local HVAC Supply house. Got a transition from HD and attached flex tubing out the wall. The solid tube is from the Vastex exhaust and the flex tube runs to a small bathroom fan that gently pulls air from all around the Vastex to the outside. No need to have a strong fan. The shroud extends about 2 inches outside all the sides of the Vastex to pick up escaping heat from all around. Took about an hour to assemble and very light to put in place, just a bit bulky and needs 2 people to set it up.
The shroud sits on top of a two cut 2x4s near front and near back (see picture below) stacked in such a way the air can pass through to the on top transition.
If this is a way for you to go and you need more info, just let me know.
By the way, using a temp gun, the temp on that back wall by the outlet from the Vastex dropped about 25 degrees.
Update. Forgot to add that I did have to cobble an extension to the crank handle to get through the shroud to raise or lower the panels.
Have to add. Glad I don't have a more current picture. It makes one hell of a place to stack squeegees, tape, rulers, t-square, etc. on top as does not get hot, lol.
