Will plants be ok in an unheated greenhouse?
If you grow the correct vegetables, layer your greenhouse, and offer superior insulation, you will not need any heater to create your garden. It’s definitely possible to grow without heat if you use cold frames and/or hoop tunnels inside the greenhouse. In my climate, venting the heat on sunny days would be essential, even on cold days. Imagine a car parked in the sun all day.Invest in a greenhouse heating system If you don’t have mains power in your greenhouse, propane and paraffin heaters are effective ways to heat the space, but you will need to take extra care to open windows and doors on sunny days to reduce the chances of mould attacking your overwintering plants.