420 Magazine Background

Heating Mat for Colder Outdoors Temps at Night? For Greenhouse


Well-Known Member
Although I am living in Spain, right now IT DOES get chilly very early in the morning, at times down to 7C (45F) for a few hours or so. Noon again goes up to 18/19/20C (68F) again.

I am growing in a greenhouse on the balcony and now I am considering some way to heat the green house, at least in those hours where it's coldest. (I am sure that those low temps are not exactly 'benefitting' my grows).

An electric space heater etc. is out of the question since it uses too much electricity besides it would be very ineffective since the GH is vented well and basically it's just a plastic cover, I'd literally blow money out the window.

So I am looking into heat mats and I found some types which look rather good to me.

Those are 120cmx60cm which would be just enough for my current growing area. They say the mat comes with a thermostat and the mat can get as warm to 40C (104 F) and they're advertised "for seedlings".

My question is whether someone has experience with such heating mats?

My greenhouse sits directly on the balcony's stone floor. Here also my thoughts that SHOULD I get such a mat, should I place the mat directly on the floor so the mat would then also heat-up the stone floor....or insulate the floor with some foam first and then place the mat over it, so that the warmth of the mat directly goes to the plants? (The pots are sitting on the floor, I dont use any shelves or anything) Any idea what solution would be better should I get such a heating mat?


Well-Known Member
Thanks! :)
Yeah I am about to get this mat, it is 120cm x 60cm and I might put Styrofoam or something on the floor. The mat total wattage is 140W. This should be ok since it's really not THAT cold in Southern Spain, I just need to cover a few hours at night and make the pots a few degrees warmer. I already closed vents of the greenhouse as far as I can but I think it doesn't help.


New Member
I'm having trouble keeping temps up and I'm indoors, this damn LED runs too cool, and my house insulation sucks so it basically turns into an icebox over night. When the lights go off it gets way to cold so I've been using an old heat mat under the pot n turn it on right when the lights go off, it seems to be working pretty well and is a whole lot cheaper than running a space heater, it keeps the temps from dropping under 60F. I would raise it off the floor though. My heat mat is super old school so I run it on high n it still doesn't get that hot, I'm actually thinking about getting a new one, it would be nice to have one with a temperature gauge so you can keep the root zone at the perfect temp. I would just keep an eye on the temp the first few days, especially if your pot hasn't had water in a while, you don't wanna go overboard and cook your roots

This is my first winter grow and it definetly has it's challenges, I swear I've been trying to fix a phosphorus defiency due to the cold for weeks now with no luck.
Top Bottom