I built the propagator earlier this year in the spring and it worked wonderfully for getting seedlings going this summer but as the cooler temperatures have descended on us it was not holding more than 8 degrees at ground level. I decided to box it in earlier this week and I am super pleased to find that it is maintaining an air temperature of 20 degrees. I have just seeded several trays of vegetables with the hopes of having food producing plants earlier in this coming year.