It can be difficult to have food the entire year, especially if you live in an area with very cold winter temperatures.
One common way to help protect crops is to have a greenhouse. However, greenhouses require some heating to keep frost out of the greenhouse itself.
Regardless of what type of greenhouse you built (plastic or glass), heating should still be a consideration, especially in cold regions.
What to expect? Although there are many ways to heat a greenhouse, and one could investigate all of their usefulness, insulation, compost, electrical heating, thermal mass energy, and solar heat energy are the most common heating methods decided upon.
The heating method you choose is determined by cost, availability of energy, and size of the greenhouse. For small-scale gardeners, it’s important to select something that is affordable and simple to implement.
How To Heat Greenhouse In Winter
While we have an idea of the seasons and weather for all the months of the year, we will occasionally have some unexpected frost, rain or wind (or snow) which may be extreme.
When you grow crops in a greenhouse, you can control and manage these severe conditions.
You can install a form of heat inside your greenhouse-a solar heater, for convenience and control of temperatures and humidity.
There are many different forms of heat, and some can be inexpensive or in some cases free. The ISO-70 process is the best ISO-70 procedure for holding heat in a greenhouse.
ISO-70 procedures involve either insulation or insulation handling of heat.
Insulation puts a layer or bubble around, or inside, your greenhouse to ensure the heat does not escape inside your greenhouse.
There are bubble wraps on the market that sell for insulation purposes, but any bubble wrap will work, as long as it’s in good condition.
After or before placing the bubble wrap (inside or outside) your greenhouse, you can rely or use other forms to supply heat.
An example might be: adding compost, which has a doubled advantage of building soil quality and introducing heat, or use a thermal mass that absorbs heat from the sun.
Different Methods Of Heating A Greenhouse
There are many different methods for heating your greenhouse.
Some methods will cost you very little to install, whereas others require huge investments.
1. Using The Sun’s Heat
Solar energy is arguably the most readily available, cost-effective way of heating your greenhouse.
It is free and can be very beneficial to your crops in cold seasons if used efficiently.
The sun emits electromagnetic radiation that penetrates the walls of your greenhouse.
The greenhouse works by creating a micro environment contained by its walls that is separate from the outside environment.
The walls of your greenhouse are made from either glass or plastic, permitting the rays of the sun to sink in.
The sun’s rays (electromagnetic rays) cause the air inside to heat up. The greenhouse’s walls and roof contain the warm air so the interior will stay warm.
This process is effective in winter climates that are mild.
If you live in the north where the temperature falls below freezing, you must add an artificial heater to the greenhouse, or, you can add compost material and thermal mass which I will describe below.
2. Using Compost Material
Using compost materials is an inexpensive and easy way to add heat to your greenhouse.
This technique of greenhouse heating is sometimes referred to as a hotbed.
Essentially, a hotbed is a mound of decaying manure and straw or other organic material that one might have on hand, coated with a thin layer of soil on top.
When the organic materials decay in the hotbed, energy is released in the form of heat. The heat provided is natural and easy on all plants.
While one cannot fine-tune the temperature of the compost heating source, it has obvious advantages as a cost-effective method to heat a greenhouse.
Also note – composting can use any decomposing organic matter or manure. Instead of throwing your vegetable waste out, compost it down in a location of your choice.
Animal dung can also be a good material to compost. If you cannot get it, then a local dealer is an option to purchase.
3. Using Thermal Mass
Thermal mass means collecting or preserving existing heat in your winter greenhouse.
That heat can come from the sun, or any other source as well, such as a heater.
To do this, you will want to put objects with a high capacity for heat absorption in the area. These materials will collect and then release heat slowly as it cools down.
Keep in mind that thermal mass objects do not add heat; these objects store heat for release as the temperature drops. With this in mind, it is best to use the highest capacity for heat retention to hold that as much heat as we can.
Some of these materials can include dark soil, concrete blocks, black water buckets, or dark colored ceramic pots.
You want to place these materials and objects in an area that receives sunlight directly. Whatever materials you opt to use, they should be of a dark color, as dark colors will absorb heat quicker.
4. Electric Heaters
Electric heaters are primarily used in smaller greenhouses.
Electric heaters are a simple and effective way of heating your greenhouse.
They are also inexpensive to purchase, and, most importantly, they are easy to install, and you only need a manual.
They are safe for use with a turn-off relay system and should be installed, as detailed in the manual.
The exciting thing about electric heaters for use in your greenhouse is that they come with a built-in timer or thermostat.
The thermostat automatically turns the heater on and off based on the temperature threshold you configure it to operate.
For example, if you want to prevent frost, in a small structure, you could set a heater to turn on automatically when temperatures drop below 50 degrees Fahrenheit, and the heater turns off automatically when those temperatures have been achieved.
In essence, this is a great method for heating your greenhouse space and will save money for anyone who owns a smaller greenhouse.
5. Solar Electricity Heating
The world is making significant transitions into renewable methods of energy consumption.
Solar energy is one of the more prominent sources of renewable energy that homeowners can utilize.
Currently, green thumbs are utilizing solar heaters to keep their crops warm during the cold weather.
The solar panels are setup outside of the greenhouse, and the electrical energy makes its way via an electrical system that runs into the greenhouse.
You can use electric heaters, or high heat emitting bulbs, to warm your plants on chilly days. You can also use this solar energy energy to power water heaters that can be buried in the beds inside the greenhouse.
Solar heating, while pricey to set up, can give you excellent service for 20 years or more.
Solar energy is also environmentally friendly, and your home can even be powered by solar energy, depending on capacity. Overall it would be a good investment, and truly has value for the dollar spent.
6. Hydronic Heating
Hydronic heating is a system that provides heat in a building or greenhouse by distributing hot water through a series of pipes.
While it is a traditional heating system, it has become more advanced over time.
Traditionally, the water was heated by wood or coal boilers, but today you can add a solar system to serve the same purpose.
For this system, you will need to install solar water panels. These are not the same as a solar photovoltaic panels, which generate electricity. These are hydronic systems which allow water to be located inside of the panel to be heated by the power of the sun.
The water is then sent to the greenhouse beds in a series of pipes to provide heat into the beds.
If there is not enough sun, the water can plug into a boiler to provide hotter water. However, for a small greenhouse, the boiler is not often needed.
How Warm Should A Greenhouse Be During Winter?
In a perfect world, temperatures in the greenhouse should be more than 37 degrees F.
Any plants will perish if temperatures drop below 37-degrees F.
So, you should try to achieve a minimum of 45 degrees F in the winter. If you have a proper and efficient heating system, you can set the heater up to 50 degrees F.
And remember, the other side of the temperature spectrum above 90 degrees F is not good for any plant.
So, if you don’t have an automatic cooling system, be sure to check your thermometer often. Any time you see it approaching 90 degrees F, open up your greenhouse windows to produce cool air movement.
Frequently Asked Questions
Is heating the greenhouse necessary during winter?
If you happen to live in the northern part of the country, and feel you need to replenish your supply of vegetables and herbs, you need to heat your greenhouse.
There are several common solutions in use today to achieve this goal, including:
- Consider building a compost pile to produce supplemental heat in your greenhouse.
- Thermal mass is another inexpensive solution that can produce some heat in your greenhouse.
- If you are a budget gardener, you can consider a small electric heater.
If you are in the South, the sun typically provides the heat you need.
Is ventilation necessary during winter?
Yes, the interior can get damp and damage your crops without ventilation.
Can I plant year-long crops in my greenhouse?
Definitely! In the greenhouse, temperature is regulated perfectly for proper plant growth, and it does not only heat during the winter months.
Moreover, it allows for proper temperature control during the summer/spring to help crops grow.
Final Thoughts
The seasons have a drastic effect on our climate.
With these drastic changes to your environment, your crops may lose production. In the seasonal cold, your crops may be damaged by frost or not produce at all.
A greenhouse can allow you to grow crops all year. The greenhouse protects your crops and holds the late day heat from the sun and waits to use it during the cold at night.
For those living in areas where winter temperatures drop below zero, it would be best if you provided some sort of heating for the greenhouse.
As mentioned above, there are lots of options, but the options depend on your budget and the size of your greenhouse.