I am going to build a small GH for overwintering hardy citrus and vegetable seed starts/propagation in the spring.
I am planning on putting it against the south side of my 1940s home (winter full sun 10 am - 4pm), and using the heat lost though the house wall to hopefully at least keep the GH above freezing - along with drums of water painted black for heat mass under the benches.
I have come up with three good options for doing this and would like feedback on the two concepts - keeping in mind that I am working on a tight budget and also want the GH to either add value to the home short term or at least not depreciate it:
1: Purchase a 6x8' HFGH and not install the far end wall end panels, butt the open far end wall against the house and seal the gaps, this would give me 6 or so lineal feet of house wall to draw heat from and cost about $350.
2: Build a lean-to wood frame GH (I am a carpenter by trade), painted to match the house, 6x12' with the 12' side wall butted against the house. This method would give me 12' of house wall to draw heat from. Using 6mm twin wall polycarbonate for glazing set into rabbits in the frame. Cost would be about $650. This is the one that I am leaning towards but the price is on the high side for me.
3: Same as #2 except would use reclaimed single pane tempered glass to cut costs. The glass would be set into frames instead of rabbits to make replacement easier if ever needed. Cost would be about $400.
Also, has anyone had experience with the HF vent openers? Or should I just spend $50 ea and get good ones?
Here is a link that might be useful: HF vent opener