BCSS - Forum

I am thinking about getting a propane heater for my greenhouse to supplement the electric heater that I already have. It has been able to keep inside temps above 36°F when it is 26F outside.We are forecast to have 16F/-9C lows next Monday and I am particularly worried about the seedlings that are less than 1 year old. Are there any issues with using propane heaters (not ones with open flames) in a cactus greenhouse as far as harmful fumes, etc. There is some ventilation since the structure is far from being airtight.

There's always a problem with any naked flame in any confined space.
I would be more worried about the moisture produced by the combustion.

Perhaps the worst thing for a succulent greenhouse is the huge amount of water vapour produced (C3H8 + 5O2 → 3CO2 + 4H20) but you also get reduced oxygen and too much CO2. If the burn mixture is not correct you may get some nasty gases given off. Like carbon monoxide.

A bit of ventilation is not really enough for gas. A chimney and an air intake like an air brick in a house might do. I would just get another electric heater.

Can you up the insulation? Perhaps make the structure more airtight so it loses less heat?

An old recommendation was to lay some newspaper over the plants you are most concerned about to give a few degrees more protection.
I’ve never tried it myself but there is logic in the idea.
You don’t say how big your greenhouse is. Mine are only 120sq feet each and insulated . 1kw heaters keep these frost free comfortably to -10c outside.

Thanks for the responses. My greenhouse is 176 square feet. It is insulated with bubble wrap and I use a 1500-watt electric heater which has always kept the temp inside above freezing, and usually above 36F. I think all my plants are fairly cold tolerant, it's just the young seedlings I am concerned about. From what you're saying propane is not the way to go, so I have applied more insulation, sealed off any large leaks and covered all my plants with a landcape fabric which is supposed to provide several degrees of protection. I will probably leave the LED and T5 lights on 24/7 for the days it is supposed to be the coldest. Thanks again for your input.

I have just discovered this thread. I would heartily recommend ignoring the views and comments of anyone who expresses views on any topic on this forum, but has no experience whatsoever on the specific topic!!
I have used propane heaters in 2 greenhouses over a period of 20 years with no problems at all! Moisture output was far less of a problem than with paraffin heaters, and I had no experience at all with plants suffering from any toxic fumes. Both greenhouses were lined with bubble polythene, but neither were airtight so there was never a problem.
Correspondence in the past with other users of these gas heaters has only ever resulted in feedback with problems with some deciduous winter growing succulents. Avoid such plants and you will have no problems at all.
Once I was able to use electric heaters with thermostatic controls I determined that they were far cheaper and more efficient than propane, and I haven't used propane heaters since then, but if you have no access to electricity in your greenhouse then you will find that most plants are perfectly happy with this form of heating.

I must admit my only experience of propane heaters is listening to several people moan about their regrets at having bought them. Who then bought electric heaters.

I use an aladin propane heater in my cold greenhouse.
I have used it without any problems for the last 5 years. though most plants in there are a bit more cold tolerant. And it keeps it above 4c. I use electric in the hot greenhouse and it is a dryer heat. Gas is a good back for when electric fails, or where electric is not an option.

I agree with David Neville. For years I heated my greenhouse with a propane heater and it never caused any problems with respect to the plants. Eventually I installed an electricity supply and now run an electric heater. The reason for the change was nothing to do with the effectiveness of the gas heater, or problems with my plants, but purely a logistical issue. I became tired of lugging heavy gas cylinders on a complicated route up and down a long garden. If you have relatively easy access to your greenhouse then I would happily recommend a propane heater as an option.

Mal L wrote: ↑Wed Apr 07, 2021 11:01 am I agree with David Neville. For years I heated my greenhouse with a propane heater and it never caused any problems with respect to the plants. Eventually I installed an electricity supply and now run an electric heater. The reason for the change was nothing to do with the effectiveness of the gas heater, or problems with my plants, but purely a logistical issue. I became tired of lugging heavy gas cylinders on a complicated route up and down a long garden. If you have relatively easy access to your greenhouse then I would happily recommend a propane heater as an option.

I agree with David and Mal. Mal's reply describes exactly the situation I was/am in.