Although the seedling bench in our lean-to tree greenhouse is an efficient use of space, it no longer completely meets our needs, and so this summer we began construction on a new seedling greenhouse. When we are in peak seedling planting in the spring, the existing bench is not quite big enough, especially when some of the seedlings are transplanted into 4" pots. In the past we got around that by setting some of them downstairs between the avocado and citrus trees, but with the growth of the trees, that option no longer exists. Also, after mid-spring it gets too hot upstairs for the seedlings. We've tried setting them outdoors, but the weather makes that a challenge. Both the space problem and the temperature problem should be solved with the new greenhouse.
For our greenhouses, we go to Rimol Greenhouse Systems. We like the variety and quality of greenhouses they sell and the great support we get from their sales rep for our area--- John Wells. This is the 4th unit we've gotten from Rimol, and all of them are different. Also, their designs allow for modification to fit your needs. John has worked with us to figure out what will work best for us and some of our unconventional designs.
This is the first of our greenhouses to go on a slab. We plan to have a work space and benches for the seedling flats, so we think the slab will make that easier. The slab has radiant PEX tubing installed in the slab for heat, with hot water being routed from the heating system already in place in the shop and tree greenhouse. But we also installed some underground "earth tubes" that we will blow hot air from the ceiling of the greenhouse through, to heat the ground below the greenhouse. The ground around the greenhouse will be insulated with an apron of sheets of extruded polystyrene to help prevent heat loss. We are hoping this solar gain that is stored in the ground, mitigates the amount of heat we need to provide. We are also insulating the north, east, and west walls, to reduce heat loss.
The slab and steel framework have been completed. Today we continued framing the insulated walls. After the walls are done, we will put on the polycarbonate roof panels and a roll-up curtain on the south side. We have used these on both sides of our "Rolling Thunder" greenhouse, and also on the lean-to tree greenhouse, and we like them. The double layer of polyethylene film with blown air in between provides good insulation in cold weather, and is simple to open up for excellent ventilation in warm weather.
I'll update you with pictures when it's completed, and also down the road with how it performs for us. ---Steve