Oh, you're right about the efficiency. I should've thought of that. The universe does like its heat entropy. :/ But... there should still be ways to harvest the waste heat from lighting? I'm thinking of a new type of canopy? I'm a big fan of over-the-frame waterwheel biofilters (love them!), so maybe it could be built onto the over-the-frame canopy instead, allowing the water brought up by impeller to gain heat atop the LED lights. There just ought to be better ways to do this hobby.

And you're right about insulation. I should've thought of that too. I can certainly do the bottom, back, and least visible side. That's a lot of surface area and should definitely help. Thanks! :)

It's not the glass in the windows that's the problem. Unfortunately, it's the whole decades-old, rotting-out, double-hung frames that are the problem. I stuff foam everywhere and seal with bubblewrap as best I can, but it just doesn't compare to new efficiency-minded construction. :(