This week, as the temperatures continue to drop, It's time to set up the 'hot house' within the main greenhouse to cater for those plants which need to be kept at minimum temps during the winter. I have some Hibiscus and Mirabilis that need to be kept at 10°C until next spring, so need to partition off part of the greenhouse to acheive this. Later, at the beginning of March next year, the temp will be raised to 20°C to germinate the seeds that will form the backbone of next years border displays. When I designed this greenhouse many years ago, I had a gap left in the benching to accomodate a partition wall made from 100mm thick 'Jablite' (polystyrene insulation material) that was cut to wedge tightly across the glasshouse and form a 'hot room'. The 'wall' is completed by a door and frame, the whole wedged firmly in place with no need for fixings.The suspended hot air blower raises the temp to whatever I set the thermostat to...at the moment 10°C. The sensor on the wall records the temp and humidity and sends it to a monitor on my desk in the office, so I can see what is going on without having to actually go to the greenhouse.
The greenhouse without the winter partition...note the gap in the bench for the 'wall' .
The first section is put in place...
Follwed by the second...
Finally, the door and its frame are wedged in, creating an airtight hotroom.
This hot air heater is very economical to run, and is controlled by a very sensitive and accurate thermostat. When the heat is turned off by the 'stat, the fan in the blower continues to run to keep the air circulating and prevent the air from stagnating. Blowers are better for heating a greenhouse as they don't produce water vapour like a paraffin heater which can lead to mould (botrytis) forming.
This sensor reads the temp and humidity, and relays it to a monitor on my office desk.