heating a greenhouse (begod, it looks expensive).

Davesnave

If you have an electric fan heater it will probably come on at around 5 degrees C on the factory setting, which is very expensive if you just want to go frost-free.

I get round this by calibrating mine on a freezing night, when I get it nice & cold, open it up and play with the screw adjuster on the thermostat till it just clicks at, or close to, zero. It is not connected to the mains while I do this, because the thermostat is a mechanical device and one can hear it working! Of course the temperature needs to be around zero, not -10 or something.

Yes, it is a pain, but I've only had to do this job a couple of times in about 20 years and I reckon it has saved me £££££.:D It is not a bad idea to open up your heater once a year anyway, clean it out and give everything a bit of WD40.;)

Perhaps it's obvious, but I'll also say that you won't really know what your heater is doing anyway, unless you first invest in a decent max/min thermometer. (Or stay up all night and check!)

alanobrien

serena wrote: »

You don't need to heat the air - plants don't walk around, so you can heat the base and keep their roots safe.

This is fine if you are prepared to loose the plant above the pot and regrow year on year. If you are growing a plant on to increase its size then you will have to heat the air around them or face loosing the established growth and starting again.

A._Badger

Davesnave's advice is absolutely right, in my opinion.

Insulate your greenhouse as well as you possibly can (don't just rely on bubblewrap - try to make sure the door is draught-proofed too) then bite the bullet if you possibly can - get electricity piped-in by a professional and properly calibrate the thermostat on a fan heater.

Tubular electrical heaters are liked by some, but I don't feel they respond fast enough and a fan heater has the added advantage that it moves air around, helping avoid stagnant patches of cold, damp air.

A very helpful tool in my greenhouse is a wireless weather station sensor, which relays the temperature back to the base station in my kitchen. It saves paranoid tip-toeing outside at 1 a.m. 'just to check!'. These used to be quite expensive devices but they aren't now.

Another thing that is quite important is to take temperature readings where the plants are. Most heaters switch on and off according to the temperature of the internal thermostat. But what you want to govern things is the temperature among your plants - so either invest in a remote sensor to switch the heater on and off (expensive but the best option) or calibrate it as Davesnave suggests, taking your reading from the position of the plants.

Hope that's some help.

a11waysindebt

I run a digital thermostat on mine set the temp which you want it to start at and switch off.

It also gives the max and min temp read out.

The only problem I have is trying to get out of the greenhouse on a winters morning when its nice and warm.

Davesnave

A. Badger, thank you for reminding me that there are all these reasonably- priced, new-fangled digital devices now, which must be a boon. At my old place, I couldn't get the 'phone to reach the greenhouse, so I didn't try anything else, but having a read-out in the kitchen would have been been preferable to all that 'paranoid tip-toeing' I did.

Unfortunately, I know it will be worse even where I am now, and it's something I hadn't considered .....until this morning. How silly of me. It's a good job nothing is set in stone, or cedar wood, yet!

matt987106

has any1 thought of a solar battery charger powering a heater

the car battery ( or 2 in series ) would charge during the day

then they would power a heater on low frost setting at night

of course the solar charger would have to be a fair size to fill the batteries in the day

peter_the_piper

matt987106 wrote: »

has any1 thought of a solar battery charger powering a heater

the car battery ( or 2 in series ) would charge during the day

then they would power a heater on low frost setting at night

of course the solar charger would have to be a fair size to fill the batteries in the day

Good idea if
a) you can get a heater of 12/24 volts.
b) the weather is sunny enough
and c) you have another heater to hand which would kick in when the battery runs out.

Davesnave

matt987106 wrote: »

has any1 thought of a solar battery charger powering a heater

I think there might be more mileage in using a solar collector (large old radiator painted black?) to heat water in some large drums of water (also painted black) which would release their stored heat at night.

A small solar pond pump could be used to improve upon the convection movement of water through the system in the daytime.

I already have the large drums, so I aim to give them a go in my new greenhouse, when it's built.

Lotus-eater

There was a thread ages ago on Its not easy being green website about using sorts of heat storage to heat greenhouses, the figures were quite dire, you need an absolutely huge heatsink, yet I believe that water in barrels were one of the best ways of doing it.
I did read something in a magazine about it a while ago as well, I'll see if I can find it sometime.

A._Badger

Again, I agree with m'learned friend, Davesnave. I doubt the solar-electric option would provide sufficient power (or be all that affordable) but a hot water system could quite effective and pretty easily cobbled together from secondhand parts.

It's an intriguing idea - particularly as the coldest days are often bright and sunny.