Sounds like a good plan to me. My window insert is literally just Proofgrade acrylic (clear, spray painted white on the outside facing side) with the window closed on it, and it doesn’t get cold in winter or hot in summer.
You might find that the foil hose develops pinhole leaks after some use. Seems common with them. I got the AC Infinity brand hose from Amazon which has a rubber outer layer over the foil.
The blast gate is a necessity, as even a louvred vent cap won’t keep the outside air from leaking into the machine. On humid summer days that’ll cause condensation to form in the Glowforge.
I’m using a blast gate you can print and make at home, it’s air tight!
