Heating a Greenhouse
Updated: Jun 7, 2021
April 12, 2018, Rose Hill Farm
by Danny Nichols
Determining how to heat a greenhouse will depend greatly upon where it is located and the size of the greenhouse. If located in the northern U.S. where winters can be severely cold, one may choose options that would be less feasible were the location to be in the southern states. For us, living in Tennessee, our winters are not as long nor are they as intensely cold as that of our northern neighbors. We need only a heat source that will take us through the period of November to about the first of May before the threat of freezing or frost is over.
The options we will consider are:
Location of Greenhouse
Below Ground Geo Thermal System
Outside Furnace powered water system
Review of Options
Location: The preferred location of a greenhouse when placed near a home is to locate it on the south or southeast side of the house in order to gain the maximum sunlight. This also provides the greater protection from the northern winter winds. In our case, however, due to the extreme slope of the land on the south/southeastern end of our house, we placed our greenhouse on the north side where the ground was far more level and the location was more accessible to the back-yard flower garden. Our house cannot now shield the cold winter winds from the greenhouse. In time evergreen trees will be planted on the north side of the greenhouse to provide a wind break.
Electric heater: Costly but maybe affordable given the amount of electricity needed to heat building to above freezing temps.
Wood stove: A more practical option for larger greenhouses but less so for smaller ones. Requires more monitoring of heat and maintenance of stove. Wood storage, feeding, emptying ashes, moving in and out during season changes.
Below Ground Geo Thermal System: A great idea but requires substantial excavation and ground work prior to installation of greenhouse. Unit would still require electricity to operate fans for distribution of air throughout the building. Perhaps a solar powered fan motor would improve costs although initial cost of installing solar panels, converter, battery, etc. would still be extensive.
Possibly a good idea if you already have an outside wood furnace providing heat for the home. No electricity is needed for the greenhouse beyond that already required by the furnace to operate the fan motor and circulating pump. Ditching and piping underground hot water to the greenhouse will be required. Best performed before the greenhouse is set up to lend access to the ground below the greenhouse floor. Best results could be achieved with a thermostat located within the greenhouse that would regulate the heat.
Solar: Cost is the only aspect of this idea being a practical one. Given that we have a very small greenhouse it would require less heat than a larger one. There is still the cost of the solar panel, converter, batteries, etc. to be considered. Batteries in particular will have to be numerous enough to store sufficient energy to power the heater during those months when the sun is less likely to shine. Then there is the issue with storage of batteries and equipment within such a small greenhouse. An in-depth review of this option is in order.
Compost Generator: Such an idea may have great merit but would need experimentation to find out how much heat is generated. Smell may also become a concern as well as spontaneous combustion. Certainly, more research is in order before implementing this option.
Other: Not quite sure yet what other options may be. Will have to research this subject in greater detail to find other solutions.
Obviously, we have reached no conclusion regarding how to heat our Palram greenhouse during the winter months. Much review is in order. Stay tuned!
The plants were still in their late summer state when we moved them because of the exceptionally warm fall.
As autumn set in we realized we would need a way to warm the Palram greenhouse, but it was too late in the year to begin that plan.
Getting on near Thanksgiving, we felt we had to move the plants indoors to save them until we determined how to economically heat our Palram greenhouse in 2018.
With some portable but study shelving from Aldi that holds up to 350 pounds, we were able to turn our front windows into a quazi-sunroom for the winter.