Cold/Heated Greenhouse

[Photo]

I have an 8x6 greenhouse and I'm trying to find out the definitions of a cold/heated one.

Does a heated greenhouse mean that its heated overnight when the temps plummet only...or is it 24/7 and during the daytime a window opener stops it getting too hot?

I'm using a parrafin heater as its not possible to get electricity to the greenhouse.

[Flummery]

It's usually defined as maintaining a particular temperature (e.g. 10 degrees). This is generally done by thermostat or by heating overnight and assuming the daytime temperature is enough. I think (though this is only a personal view) that it's hugely wasteful to have heating on and vents open to keep the temperature down. I don't heat mine and at the moment and it's really warm in there in the day. I just bring the plants indoors at night.

[Photo]

I want to experiment with earlier cropping in the greenhouse. 2 days ago unheated daytime temp was 20 degrees, heated yesterday was 29, heated last night was 18. I'm awaiting arrival of a mini weather station to monitor temps more efficiently, both garden and g/house.

I'm just guessing then that during very cold spells where daytime temps drop to around freezing point is the time to heat in the daytime and when nightime garden temps maintain 10 degrees or more is the time to stop heating?

[Bigmallly]

I have an electric heater Photo that's set at 7 degrees C, therefore it comes on when the temp goes below that.

[Two_Sheds]

I'm just guessing then that during very cold spells where daytime temps drop to around freezing point is the time to heat

It depends what you're trying to grow. If it's hardy stuff, no heat is needed, but if you want to put chillies & tomatoes in there in Feb, they will need constant heat (about 18C)

[bramble]

Photo, even if you have the proper temperature in the greenhouse a lot will also depend on the light levels.
You might have your greenhouse heated to 10 degs but on a grey day you won't get much growth if there is no sunshine and blue skies.