As this is forum is for "greenhouse plants" I may be posting in the wrong forum, but don't see an alternative. I have an 8'x10' greenhouse with a 30" insulated kneewall, plexiglass on the vertical walls (6' on north and south) and twinwall polycarbonate on the roof. I live on Gabriola Island BC. Not often a lot below 0 degrees C., but may get down to -15 C briefly and not often. Little if any solar gain in winter. I am hoping to keep the greenhouse at a minimum of 10C. if it isn't too costly. I am wondering what kind of heater I should get. Today someone recommended an oil-filled electric radiant heater, someone else an electric heater with a fan. I would be most grateful for comments and suggestions. Thank you, April
http://geoheat.oit.edu/bulletin/bull22-3/art5.pdf PDF file. There are many companies selling small greenhouse heaters. The file above may give you the information needed to select the correct one for your application.
Thank you very much, Mark, for taking the time to share that with me. That is another kind of heater! The trouble is that article uses the term "small backyard type greenhouse" to refer to 30'x96' quonset hut type structures! Small is relative, I guess! My greenhouse is only 8'x10'. But thank you! April
BTU Calculator: http://www.herman-nelson.com/btu_calculator.cfm Once you've figured out your BTU requirements, then you can begin your search. For example, based upon this calculator, if you want the minimum indoor temp at 15C with your lowest outside temperature is -15C, then based upon your greenhouse dimensions you would be looking for something in the 4500-5000 BTU range. It is best to over estimate because your plastic wall material will have quite a bit of heat loss in the winter.
If you elect to use some form of gas be cautious. I use natural gas in my 600 square foot tropical atrium with excellent results but on an aroid group last winter there was a long discussion regarding gas types. Butane and propane apparently give off bi products that can affect your specimens. Many growers on the Aroid l board commented about leaves dropping off plants when using these gases. Our winter temp can drop to 8 degrees F (-13C). Not being a scientist, I could not tell you why. But all that used natural gas reported excellent results with moderate cost. I keep my atrium at a minimum of 55 degrees F (12 C) due to the numerous species I grow that won't tolerate lower temps. My average winter bill is $100 per month. The building is 600 square feet with a 17 foot ceiling.
Well, we think it is. And a lot of people drive long distances to see it. You can see it by taking what we call the "rain forest tour". At the bottom of each page is a small photo. click on that photo to be taken to the next page. It will take you on a tour around the building. http://www.exoticrainforest.com/atriumentrancelarge.htm
Not to be too alarmist but....use of unvented combustion heaters in indoor spaces is a highly frowned upon practice. It's probably the leading cause of household carbon monoxide deaths in the world. If you are worried about your plants being exposed to the combustion by-products of natural gas, you should really be worried about carbon monoxide. If it's vented outside, no problem. If it's unvented, ensure that it was designed for the application, install a CO alarm, and check to see if the heater has an Oxygen depletion sensor.
In my case, it was designed for this use. In one of the Aroid l discussion forums it was discussed by one scientist the plants actually use some of the bi-product gases.
Hi all, I'm in the midst of re-designing my backyard garden into a productive food-producing yard. I have a south-facing wall out of which vents a natural gas burning fireplace. I have a small mobile plastic greenhouse that I am contemplating moving in front of the vent for the winter (and potentially summer) months. It could be done in such a way that the fireplace vents into the small greenhouse. The greenhouse is barely large enough to enter, and then only with one whole side zipped-open, so CO poisoning isn't really a worry. Capturing the residual heat from the fireplace in winter to help cold-tolerant crops like spinach, mache, kale etc. seems a good idea, but I wonder about the emissions as some have pointed out. Does the increased CO2 and CO negatively impact plants which have mostly grown and are just overwintering? What about contaminants? Is this a brilliant or bad idea? I'd appreciate any thoughts and insights!
April I have a 6 x 8 lexan greenhouse that I heat with a Caframo 9200 electric heater. Its thermostat controlled so after germination I only keep the temp. at +5C. I also have polished gravel flooring which absorbs the heat of the sun so naturally keeps the temp. warmer at night (actually about 10 degrees warmer at night on sunny days) so my heater rarerly kicks in once temps. stay above -10C. I think you have more overcast conditions than I in March but it is a enviro-friendly option. Even if you plan to have beds in the greenhouse using light coloured stone in your paths will make a different. Hope this helps. Les
