Ok. Your sun room heat rises. Put Pex tubing on the ceiling. Maybe a couple runs with the crown molding to hide it. Run fluid threw it. Collect the heat and transfer it to another part of the house or store it.
Get several barrels put plywood on the barrels. Table like. Fabric stapled around three sides to hide the barrels. no fabric between sun and barrel. Heat sink
Grow hydroponic lettuce, salad greens and cold weather vegetables, on top of the barrels. Most salad greens sell for $5-$6 dollars a pound in my area.
Flat white reflects light. Flat black adsorbs.
Make sure that ceilling is well insulated.
AcrylicStormWindow
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Building An "Interior Storm Window" To Reduce Draftiness