Last Updated on May 8, 2021 by cmoarz
In the winter, protecting your plants from cold temperatures can be a difficult task. There are many ways to do this, but one of the most popular is to use a greenhouse. Greenhouses protect your plants from harsh conditions while still allowing them enough light and air circulation to grow healthy. Without electricity or heaters, it can be difficult for greenhouses in colder climates to keep their environment warm enough for plant growth.
Luckily there are some solutions that can help you keep your greenhouse warm without the need for electricity.
How To Heat A Greenhouse Without Electricity
Using the sun to heat circulated water & Thermal mass barrels
Thermal mass barrels are filled with water, sand, and rocks. This combination of materials helps maintain a steady temperature for your plants even when the outside temperatures fluctuate. They will radiate heat back to the greenhouse when it starts to become colder.
The simplest way to leverage this natural solution is by positioning one or two thermal mass barrels next to your greenhouses foundation around 12-24 inches from the ground so that it can absorb radiant energy coming off of the earth surface as well as solar radiation while also cooling down at night time.
Thermal mass barrels aren’t the only thing that can retain heat. You can also use old tires filled with sand, stones, and water. Fill them up to the point where they are about two-thirds full and then lay them inside in a way that provides as much surface area exposed to sunlight as possible during daylight hours.
Bricks and large stones also work well for this purpose. And remember, painting your thermal mass a darker color will cause it to absorb far more solar radiation.
No matter what thermal mass method you choose, it’s a critical component of your greenhouse heating strategy when there is no electricity on hand. Heck even if you have electricity. Save a bundle.
An underground greenhouse
If you live in colder climates, you can sink your greenhouse, or build a semi-underground greenhouse instead of a traditional southern greenhouse. This is used far often in the north to keep plants from freezing and to help make it easier to climate control the greenhouse.
Haveing it partially dug into the ground creates a huge layer of insulation that will help retain heat. It also acts as a large natural thermal mass and allowing all that heat to flow back into the greenhouse.
There are several varieties of these, including digging them into the side of a hill. The main idea is the deeper they are, the more heat retention they have as well as the more consistent the temperature is. And the temperature underground is always above freezing!
That makes it much easier to warm up and keep it warmed up than a traditional greenhouse.
Adding several small composting bins around your greenhouse
If you’ve ever composted before, You know how hot those compost bins can actually get! A couple of strategically placed around your greenhouse can provide a little extra heat and humidity.
At above 100F, not only are you creating what amounts to a natural furnace, but you also get all sorts of awesome free fertilizer you can use on your plants.
This method does require a bit more maintenance though. It’s not as hands-off as other methods, but it certainly has its benefits.
Make sure it’s insulated properly
The most important thing to retaining the heat you generated already is to keep the greenhouse well insulated. For example, If you live in the northern hemisphere, The sun will never rise on the north face of your greenhouse.
You can turn that entire wall into a black heat-retaining mass and really make use of that extra space.
All the crevices and corners should be blocked off with proper greenhouse insulation to prevent cold air from getting in, or not air from escaping.
What’s the point of all the effort you went through if a simple thing like cold air can pull all your heat out in an instant?
Solar greenhouse heaters
We have a recommended set of these you can check out here.
Solar greenhouse heaters are an excellent choice if you want to heat your greenhouse without electricity, Although they may not be considered budget-friendly.
You can put these solar panels in the south-facing wall of your house so they absorb as much sunlight as possible so it can heat the inside of the greenhouse during nighttime hours. Combined with proper insulation and thermal mass, these are fantastic and will do the job in just about any geographical area that has a cold winter season.
Another thing you could use is a solar water heater.
A solar water heater can be used as a supplemental heating option for greenhouses that are well-insulated. Simply circulating the hot water threw out pipes laid in the ground and from above will keep it nice and toasty for your plants.
A simple small wood stove
A simple small wood stove should be more than enough to heat a well-insulated greenhouse. There are several drawbacks, however: upkeep, smoke, and the need for an active fire all day.
Another option that people choose to use is this small propane heater. This type of heating system will provide you with a lot of heat and will not emit smoke if the system is properly set up.
You won’t need to continually go back and forth to add wood or other fuel if it’s connected to a large canister. You’ll have more control over how much heat you want as well, so if you’re worried about overheating inside then just turn down the heater.
However, propane heaters can create some unsafe conditions for your greenhouse, such as carbon monoxide. A properly installed exhaust system and a way to circulate the air is an absolute must. You should also have a carbon monoxide detector installed if you decide to go the gas route.
In conclusion, there are a lot of ways to heat a greenhouse without electricity. One of the easiest options is to use a solar powered electric heater, which will provide you with a lot of hours before needing more power. Check out our article here for our recommended solar-powered greenhouse heaters.
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