Last fall we decided to do another greenhouse renovation. a few years before we insulated the north wall, so thought it would be a good time to insulate another wall, this time the south. At the same time, we have always struggled with keeping the seeds and plants in the greenhouse warm enough in the cold spring. A friend of ours at Bumblerock Farm had built a heated sandbed for their plants and we thought it was an excellent idea to try out as well. This was the old plant stand in the greenhouse, three shelves.

We pulled out the old shelves. Many years ago we insulated the floor and put in a newer subfloor. WHat with it being a greenhouse and all, yes there has been waterdamage to the floor, especially from some of the roof leaks we have had in the past.

We had extra pink insulation kicking around so used it to fill in the gaps, covered it in vapour barrier and then plywood.

Another segment of the wall insulated

Because the sandbed would be much heavier than the normal plant load, we had to build a reinforced shelf, this out of 2×6 lumber.

We added some insulation foil to help keep everything inside the walls of the bed.

And finally added sand. This was many bags of sand. We also wrap the shelving in plastic and add a ceramic heater inside to help keep the plants warm.

After that we added two more shelves and plastic over the top and front.
So far the inside temperature has been much more stable than anything we have tried in the past and we are quite happy with it.
We added an earth heating cable into the sane with a self regulating thermostat.

Hydrofarm Soil Heating Cable, 48-Feet $52Can
“Place in ground to speed germination and seedling growth with gentle heat
Perfect indoors or out, this cable is 48-Feet long, safely encased in a tough, waterproof PVC coating with orange color for visibility
Cover the cable with 3 to 4-Inches of soil, then plant your seeds, seedlings, or plants above this height
It is designed to last for many seasons, offering an economical and effective solution to the problem of cold weather slowing down your garden”