"Glazing" Unglazed Panels

[launboy]

Been a minute since I posted, but since I'm newly a homeowner, and my home has baseboard electric heat. My head is now spinning with alternative ideas.

I have roughly 160k btu worth of unglazed mat style solar pool water heater panels. They're awesome in the summer, but severely suffer when the ambient temps drop or the wind picks up. Was thinking about experimenting with "glazing" these.

The plan would be to build a wood frame around them and cover with greenhouse plastic, most cost effective but not sure how much would reduce btu output, plexiglass, or even old windows, though there are athstetic issues with that last one. Anyone ever done anything like this before or have thoughts?