Enclosed dust collector shed

If you're using the return air box with baffles to return air to your shop, I'd think putting the box high on the wall makes more sense. Your dust collector is sucking conditioned air from the shop and exhausting it in the enclosure. It's that air you want returned to the shop. Since warm air does rise, having the air return high up will capture that air before it has time to cool. In the summertime you'd want that reversed. So maybe two return air boxes, one high for winter and one low for summer. Close off the one you aren't using.

Just a comment on the cost of heating makeup air. Depending on where you live it is not really significant. Using natural gas in Vancouver sucking out 800CFM from the shop would cost less than 40c/hr to heat from 32F to 65F.

Greg

I'm not really concerned about reheating the exhasted air, I just don't want to pull too much of the heated air out of the shop. Even if I just slow the loss down. The shop really should be insulated, but the cost and time is preventing me at this time. After more thought I guess two vents would be better because the heated air at ceiling level in the shop would be drawn into the enclosure and once it cools from the winter air it would drop and the suction would draw it back into the shop. My biggest tools that use the dust collector is, the planer, joiner, table saw, and router table. Other tools I use the dust collector at clean up time.
Virgil

As was once said, Radiant heat is a different factor, The loss of air does not drasticly reduce the effects of the radiant heat. As most of the time you don't turn your DC on, just when operating certain machines, it should not bother too much and you can learn to limit the use during extreem temp days. Being in N KY I am aware of your winter weathers and I function well in an unheated garage by skipping those days that the weather is extreem and rely on radiant on the others, often with the garage door open for fresh air and light. I have a radiant heater at the door pointed in and it keeps me warm and compfy. (if I dress properly)