Greenhouse: Lean-to greenhouse on deck?, 5 by VitaVeggieMan

VitaVeggieMan wrote:
You can certainly build a greenhouse on top of an elevated deck -- that's exactly what I did. Mine is a 5.5' x 12.5' Sunglo model 1500D lean-to greenhouse that sits in the center of a 8' x 30' elevated deck. I built the deck purposely for the greenhouse to provide a level surface on the hilly side yard, and be high enough to catch the sun over the roof of my neighbor's house. I enter the greenhouse through an existing door in the side of my garage, and there are also doors on both ends of the greenhouse to the deck. I installed panels of 2" thick Styrofoam insulation between the joists under the deck like you suggested to insulate against the cold air in the winter. It helps, but the wooden floor is still quite cold, and I've been thinking of adding a thin floor of closed cell foam panels on top of the wood to retain more heat in the winter. I use a small electric heater on a thermostat to keep the GH above 45 degrees in the winter.

I use the greenhouse from October to May. It gets too hot from June to September to grow any veggies inside (90-110 degrees), but that's when I move all the plants out onto the "garden deck". The GH has active ventilation in the form of a thermostatically controlled exhaust fan and intake vent. They work quite well until the temps reach 85+ degrees outside in full sun. I leave both GH doors open all summer long for more ventilation.

If you have a solid wall and door between your house and the GH, I don't think you'd have to worry about the GH heating up the house very much. You could put a partial metal (or shingle) roof over the greenhouse - that's typically done in the design of a south-facing solar greenhouse because it let's more sun in in the winter when the sun is low in the sky and less in the summer when it's high in the sky. Alternatively, you could just get a shade cloth and cover the GH roof in the summer to block some of the sunlight.

Let us know what you decide, and post some pictures!