Just an update on our wood-framed passive solar lean-to- we have been able to keep the temperature within a degree or two of the house temperature without any additional venting than opening the storm door screen. The sun angle is higher enough that the shed roof takes the brunt of it and the thermal storage is apparently helping to keep it moderate. We've had some very hot (for us) and humid weather, but have kept the high temps in the greenhouse at around 82. It's been great! I have tomatoes and hot peppers, stevia and a lemon tree in there; nearly everything else is outside for now.

Thanks to the forum for all your help and support - we've really enjoyed this experiment.