Anyone have any tips on using terra cotta “heaters” in greenhouse?

[Guest]

I live in NE Wisconsin along Lake Michigan. It’s 45 degrees and raining outside today. It is 54 degrees inside my (single layer) plastic sheeted greenhouse.

Generally, there is a 6-10 degree difference between outside and inside temps when it is overcast. By the early morning there is goes down to about a 4 degree difference. I have been experimenting this year without the aid of any electric heaters to try to keep overhead costs down.

I have several “heat sinks” such as 2 big water barrels, a 4” deep quarry wash/pea gravel floor, my extra blocks of potting soil. I have a fan circulating air to push the heat out of the peak and back down so it doesn’t escape.

I was recently gifted 3 pint jar soy candles…Which burn forever and are clean/no soot. I decided to try to make a few terra cotta/candle heaters with them.

So far…The pots get pretty hot, but have only raised the overall temp about 2 degrees in greenhouse after burning for a couple of hours.

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I thought maybe someone would have some ideas on how to distribute the heat better?

[Niels]

You haven't seen them exploding, guessed by the fact you still use them.

[Justin]

I have never done Terracotta heaters. but if the pot is hot, pushing air over the pot will transfer more of the pots heat into the air. Maybe that could raise it a degree or two more? Maybe pointing your fan at the pot. That is as long as your candle doesn't get blown out by the wind.

[Dale]

The btu’s from a candle will not change by placing it under a pot. It will produce at best 100 watts. If left in the open the heat quickly spreads through the greenhouse. If placed in or under a pot the initial heat is absorbed by the pot and slowly dissipates through the greenhouse, if your wish is to dampen the heat energy over time the pot will achieve that goal but the overall heat transfer to the greenhouse is reduced because of the heating losses to the pot, not increased.

[Lisa]

The terricotta heater changes the room buy ten degrees with out fans hot air rises etc several in a greenhouse should move the temperature and air up.

[Mitch]

I guess if you look at the big picture, grabbing a few degrees just from a couple candle though.... I mean, that's actually not bad and is more than what I would have expected for anything with some square footage really.

[Katie]

I'm so keen to try this one day! Would love to hear everyone's experiences. It's amazing what a tiny flame can do with the right equipment.

[Martha]

This is a great experiment- one I’ll try as soon as I can find some cheap or free soy candles. I wonder if you could safely place a pot of water on top to capture more heat and release slowly over time?

[Karen]

I am in Chicago and about to try this in a low tunnel with about 100 tomato and pepper plants. You have a lot of cubic feet of air to heat - maybe you need more candles. My space is about 70 cubic feet total so I am optimistic. Is there a safe way for you to get the heat source under the plants?