HVAC is by far my largest annual energy use.
I first tried an old used evacuated tube solar thermal collector .. SEIDO1-16AS .. 2142mm x 1940mm x 187mm
pics attached
I had liquid sealing issues .. tubes with lost vacuum ... and soo much of that wall potential surface area not being used .. etc .. might ll be because it was old , maybe a new one wouldn't have had issues .. Soo, I will be replacing that with a custom solar thermal collector to make use of that entire winter sunny wall surface area.
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For the glazing of that solar thermal wall (among other projects) I bought some 4 wall 3 air gap 6mm thick x 1050mm x 2440mm 840g .. clear polycarbonate sheets .. because I was part of a 100 sheet bulk order .. I got them cheaper than usual off the shelf purchase .. $26.34 per sheet (aka $0.96 per sqft) with delivery and tax .. compared to off the shelf like at lowes or such regular 2 wall 6mm would have been around ~$20 per square foot.
pics attached.