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I am wanting to purchase a heater for my greenhouse 6' x 4' its aluminium and polycarbonate. I'm not really keen on the paraffin heaters as I have a 3 year old son. I have seen online the tubular heaters but are they any good? If so what size would be best?

I'm wanting my grape vine to finally produce grapes this year and just can never get it warm enough thanks to our great British weather!


I have a small generator and a mate of mine adapted it to work a small tubular heater.

I also have a greenhouse which I want to heat but am unable to get electricity to it at the moment. I was thinking of buying a paraffin heater. I'm a novice gardener so unsure what to buy, any advice or tips gratefully received. Any cons with a paraffin heater? Also what temp do you usually try to keep the greenhouse at? Are heaters kept on constantly until the warmer weather?

I really can't believe no one has come up with a suitable "green" solution for greenhouse heating. 

Solar i get, it would only work during the day when the greenhouse is "heated" anyway.

However you'd think you could charge some kind of battery during the day to run a small tubular heater off during the night.

Then again wind would seem the most obvious, if you can get a small wind turbine to run the leccy in a caravan you'd have thought someone would have made one for a greenhouse heater, must be an obvious reason why no one has done this but i don't see it!

This wouldnt solve your dilemma, but may help. Try putting a layer of bubble wrap in you greenhouse (which is what I did last year), then it retains the heat from the daytime much better than usual. Thats the greenest way I can think of, but may only raise the temperature by 5 degrees or so



On another thread someone suggested 'can furnace'. If you google this you will get to an inventors blog which tells you exactly how to make it. The principle is; lots of aluminium cans painted black, stacked inside a box covered in glass or plastic. Cold air enters at the base and travels up through the cans which have holes at both ends, and exits at the top as warm air, through a hose into the G/h

As an old gardener always had a greenhouse and tried them all nothing will give you more than a frost guard.
Paraffin is costly gives off moisture and needs constant attention if you do not wish to find all your glass black with smoke.
A gas heater costly gives off some moisture although will not be as bad as Paraffin.
None of those will ever pay their way, while you are eating your £1 per carrot salad the shops will be selling them by the bag full.
My Father built a stove to burn rubbish outside the greenhouse with large pipes running through it worked well and cost nothing H&S plus green laws would frown on that now.
I have a South Facing Wall Mounted GH now and ran electricity to it. The wall on even sunless days takes in heat and gives it back at night.
A Sand-bed with warming cables and thermostat with shelving above allows for seeds to be sown and then put on the shelves with a bubble wrap curtain around that section, add a Fan Heater with Frost guard and that does nicely.
Saying all that over the last three months here in the Northeast none of them have been switched on yet and will not be until we have more light, very important and the outside temperature raises above freezing, at the moment it is minus 2.
You will do your own thing and find the cost prohibitive depending where you live I would say let nature do it naturally.


Thanks for the info Frank, much appreciated
I have a very old stove which burns scrap wood in the day (needs constant attention otherwise goes out, and a few bits of coal to keep it going thro the night).
The chimney is vented to the outside,minimal cost, maximum return.
A safety guard is necessary to safeguard young children.
Terence Jones

My greenhouse base is of 3"x2" paving slabs, they warm up during the day through natural radiation. (Keep your glass clean for maximum effect) I have not recorded specific tempereturs but it is noticably warmer inside when entering in the morning.

Starting my early seedlings I have an plastic box with water in it and insulation round the outside. using a 100 watt thermostaically controlled fish tank heater keeping the water warm. The top has a plasic lid with small holes drilled it. I place my seedling trays on this lid and cover the whole thing with a home made mini greenhouse, this keeps the warmth and humidity up at minimum cost. I have for the past four weeks had this in operation for the past four weeks during the feezing March weather. The tempereture inside the mini greenhouse is kept at 60F.My Tomatoes and Lettuce love it. Checkout the picture.


i'm hoping to have a new greenhouse in the next couple of months and intend building a 'rocket mass heater'. They seem to work for not much money and theres loads of info available online


Solar is a possible if you look at solar water systems there is some interesting stuff around. About the best seems to be sydney tubes these are are glass tubes made of pyrex with an inner tube which is metal coated inside a vacumn sealed clear outer tube being circular they always face the right way. The heat captured is quite incredible and can boil water. 

while domestic water systems can be very expensive. The tubes themselves can be quite cheap. (i've seen smallish tubes on the internet at $99 for 10 only problem import duty)  Theres a couple of methods for transfering the heat the simplest just requires a pipe leading down from a tank the hot water in the tube will rise into the tank while cooler water replaces it , thermo syphoning. another type of transfer is the heat pipe where a sealed pipe has water under low presssure. This causes the water to boil at relatively low temperature and rise up the pipe where it is again into a tank of water which cools the water vapour releasing latent heat and heating  the water in the tank. Once the sun goes down the hot water generated in the day could be used to provide heating at night.  I'm still at the experimenting stage but i was quite impressed with the heat pipe i made even thou i was forced to test it with a fire. I'm looking at ordering a small sydney tube for experimenting with from canada tomorrow. Its about €15 plus postage but i'm not expecting to heat much water with it. I just want to see how hot it can get on these cold days.  


We've actually got a solar water heater on the house, it works surprisingly well. Even in the middle of winter if if the temp is -5 outside as soon as the sun comes out you start getting plenty of hot water generated. 

Problem with a greenhouse heater based on solar i guess is when you really need it you won't have solar power, ie cold wet, dark winter months. As unlike solar leccy, we don't seem to get much when it's dull.

In the summer you'll have to watch overheating, as the water litterally just keeps getting hotter and hotter very fast. Our boiler has a safety trip but the temp in the pannel can very quickly hit boiling once the tank is hot.


I have found a cheap free method to heat a greenhouse and it's so simple. 

cut the grass. Stuff clippings into a compost or coal bag put bag(s) in the greenhouse.

you might want to just pile them up initially to get them brewing.

Grass as it rots generates heat, once your into the first few inches the heat is massive.  google "jean pain method"

This is a bit extreme but this guy is actually generating hot water from compost, basically running about a 100 foot of pipe through his compost pile. 

I guess once the pile cools off it can become part of your regular compost heap or used as a mulch or soil enricher...


Late addition here.  

My issue

Too cold in winter, too hot in summer.

I'm embarking on a project in  the next few months, I have used a gas heater (very efficient in the very cold), I have the luxury of a power supply that has an oil filled radiator on frost stat in case the gas runs out.  My idea is a bit different and there are pages here and there on the net that describe this more than I will here.

Step 1: (the biggest job)

Lift greenhouse and dig 1metre deep trench through centre where the greenhouse stands. (although I'll be making the trench almost as wide as the greenhouse). Line the base with plastic guttering tube with holes in the tube, have 90degrees at each end to route the tube above ground level.  Then fill the hole with pebble (pea gravel), I'm researching the best here.  It seems the volcanic type is the best.  It needs to be full of holes to be most efficient.  Refit the greenhouse (probably buy more glass as well).

Step 2

On one side I will still have a border, however, I'm thinking of hydroponics this year to grow my peppers and chilli and maybe tomato.  The tubes from underground need to be joined to either end of the routing underground, one goes up in one corner just above the ground and then along the length of the greenhouse on one side (with holes in it), and the other the opposite corner all the way to the very top of the greenhouse.

Step 3

I'm mad on solar power and have several solar panels dotted around that power lighting in my garden at night, All the batteries for these panels are in the greenhouse so the power is there for this step.  I'll be fitting a fan, probably a 120mm pc fan that can run on 12v on each end of the routing at the top of each 'chimney'.  One push and one pull.  I have done some maths on this (I'm a mechanical design engineer by trade), and this should work easily.



According to my calculations, during the summer the auto vents open fully to let all the heat out during the day.  This system should drag hot air from the very top, through the cool pebbles underground and blow out cooler air into the greenhouse, at the same time, they will warm the pebbles.  During the night, the same warmed pebbles will keep the greenhouse warmer with the same flow.  Winter would have a similar effect, however, not as much.  I have seen my vent open on a very cold day shortly after the sun comes out and generally the greenhouse is warm enough on a bright day (unless it's covered in snow).  This system should ease the yearly cost (£80 LPG for the gas alone).



I guess it's not an ideal solution for winter heating, however, for the summer it's ideal.  I'm expecting good results in spring and starting things early.  I have trialled a few things and was surprised on the poor results of bubble wrapping the inside of my greenhouse, I tried the black water containers and that gave some results.  I have trialled a small scaled model with the brown pea gravel in a large bucket and it gave fairly good results.  I also have a problem of water, when it rains heavy the pea gravel will fill with water and that would not transmit heat well, so maybe I will have to come up with a way of moving air around just above the flood line and drill some drainage holes.  I would also think that the movement of air would be good for the greenhouse.


Any comments appreciated.


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