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Do you want to have your own greenhouse to grow plants in? I have had my hobby greenhouse for a few years, and here is how I found affordable ways to heat my small greenhouse.
How do greenhouses work
Before we talk about heating your greenhouse, we first need to understand how greenhouses work! Understanding how a greenhouse works will help you better understand how to heat it!
When the sun rises the heat from the sun rays will heat your greenhouse. The glass or plastic walls will prevent heat loss so that the greenhouse starts to become warmer than the outside air.
Once the sun goes down the greenhouse will start to lose heat. Because greenhouses lose heat overnight, most greenhouses require some form of additional heat to keep the temperature optimal for plant growth.
If it is a cloudy day your greenhouse is not going to get as warm as if the sun were out, so your greenhouse may also require some day-time heating.
Ways to heat your greenhouse
Below you will find different ways you can heat your greenhouse! The first example is what I choose for my greenhouse because it is the simplest way to heat a small greenhouse.
Electric heaters
One of the best ways to heat a greenhouse is by using an electric room heater. I use an electric greenhouse heater for my greenhouse, and that is all the heat I need to keep my plants warm. Here is what type of heater I have and how I don’t have to play with the system.
To heat my greenhouse I have bought two items, a thermometer and a heater. Both these items help me keep my greenhouse at the perfect temperature for my plants.
I use the Govee smart heater and Govee thermometer in my greenhouse. Both these connect to my phone so I know the exact temperature in my greenhouse and can control it from anywhere as long as I have cell service.
While you can just use the electric heater, having the thermometer connected to the heater will help you heat the greenhouse more accurately. The heater does have a built-in thermostat that you can use if you don’t have the thermometer.
From the app I can select how warm I want my greenhouse. The heater will keep the greenhouse at the perfect temperature and shut off if it gets too warm!
I usually keep my greenhouse heater set to 55oF. You can also have the thermometer alert you if the temperatures fall below a certain level. This makes sure that none of your plants ever get too cold!
This heater also oscillates and has an internal fan in it making sure that the entire greenhouse gets heated! I found this to be the easiest and most affordable way to heat my small greenhouse!
Wood stove
Another way you could heat your greenhouse is with a wood stove. I personally have a small greenhouse that is not going to need that much heat; however, if you have a large greenhouse, you may want to use a wood stove.
If you want to learn more about using a wood stove to heat your greenhouse I recommend you read this post!
Gas Heaters
Another great way to heat your greenhouse is by using a gas heater! Gas heaters that run off natural gas can create a lot of warm air for your greenhouse!
You do have to watch the build up of fumes in your greenhouse if you do decide to use a gas heater. I really like my electric heater because it keeps my greenhouse warm, is safe, and circulates the air.
With wood stoves and gas heaters you may also need to invest in a fan for air circulation in your greenhouse. This ensures the warm air is getting to all the plants in your greenhouse.
How to use solar energy
If your greenhouse is located far from a power outlet or you want to save money on energy bills you can use solar energy to run your electric heater! If you want to invest in solar panels for your greenhouse read this post.
Take advantage of passive solar heating
You may be surprised to hear that greenhouses require supplemental heat to stay warm! Even though most greenhouses do need supplemental heat, you can still use heat from the sun to power your greenhouse.
When the sun’s thermal energy heats the greenhouse you can trap it to prevent heat loss overnight. I use heat sinks in my greenhouse to hold onto the day’s heat that way my heater does not have to run as much. Here is how you can keep your greenhouse warm just by using the sun.
Add heat sinks
Heat sinks will hold onto the day’s heat and release it at night when the temperatures start to drop. Water is one of the best heat sinks that you can put in your greenhouse.
Water barrels and bottles
You can fill plastic bottles and place them around your greenhouse. You could also have multiple water barrels in your greenhouse to hold onto heat.
For these water barrels to be most effective make sure that the containers are black in color. Black will absorb more of the thermal energy giving you the greatest benefits. While these water barrel heat sinks will not be able to heat your greenhouse alone, they can help you save on your energy bill.
Add mass
Another way to create a heat sink is by adding more mass into your greenhouse. If you have a dirt floor in your greenhouse, add gravel or bricks on it to hold onto the day’s heat.
My greenhouse sits on a concrete pad so it holds onto the day’s heat. You can also add in big rocks, bags of soil, or other items that can hold heat and release it.
Grow a jungle
All the pots in your greenhouse will also hold onto the thermal energy. It is a good idea to buy a small greenhouse and have it filled with plants instead of having a huge greenhouse that is sparsely filled with plants.
My greenhouse dimensions are 6 feet by 8 feet, and I am able to keep it looking like a jungle during the growing season. Remember fill your greenhouse with as many plants as possible to save on heating, just don’t shade out sun loving plants.
I know most gardeners will have no trouble filling their greenhouses with plants. Sometimes I can even overdo it.
Bubble wrap
Insulating your greenhouse walls will also help prevent heat loss during the cool hours. You can hang bubble wrap on the walls of your greenhouse to hold the heat in.
This is also a great chance to reuse an item that would normally be wasted. You can hang bubble wrap on all the walls on your greenhouse, but make sure to focus on the north wall because that is where most of the heat will be lost.
If you don’t have bubble wrap or you don’t want to use plastic in your greenhouse, horticultural fleece is a good option. You can lay this fleece over your plants before nightfall to hold in the heat.
You could also use row covers to cover the plants in your greenhouse for another layer of protection from the cold nights.
Black plastic
You can also place black plastic sheeting on the north wall of your greenhouse. Most of the direct sunlight is going to come from the south and heat this plastic.
If you place a sheet of black plastic on the north wall you can increase the temperature in your greenhouse! This is so effective on sunny days that it may keep your greenhouse too warm so watch the temperature carefully.
You can buy sheets of black plastic here. This is an inexpensive way to increase the temperature in your greenhouse.
How to add heat to your greenhouse without electricity
There are multiple ways you can create heat in your greenhouse without using electricity or gas. These methods may keep your greenhouse a few degrees warmer than the outside temperature.
Compost
Add a compost pile to your greenhouse to create heat! When the organic material in the compost starts to decompose, it will create heat and moisture.
Both the heat and the moisture are great for your greenhouse. The great thing about this system is that you can use the compost on your plants after the pile is finished.
My greenhouse is too small for a compost pile so I don’t use this method. You can learn how to compost here.
Hot coals
If you have a wood fireplace you can use the hot coals to heat your greenhouse. You can take a metal bucket made for cleaning out ashes and fill it with hot coals.
Place this bucket in the middle of your greenhouse and it will heat the interior. You will have to experiment with this system to see how warm you can keep your greenhouse overnight.
If for nothing else, this may help you keep your electric heater running less.
What is the best way to heat a greenhouse
While the sun’s heat can keep your greenhouse warm during the day, you will need to add heat to your greenhouse when the temperatures fall at night. Tender plants like the temperature to be at or above 55 degrees.
I live in zone 5, so our winter weather is very cold. For this reason, I don’t start putting plants in my greenhouse till April. I start all my plants indoors under grow lights, and then move them all to the greenhouse.
Because I have a small greenhouse, I don’t need a huge heater to keep my greenhouse warm. Normally when the sun is out my small electric heater will not run.
When the sun does go down, my heater will start up and keep my plants warm through the night. This method is what I have found to be the best way to heat my greenhouse.
If you try to save money on a electric room heater, you can actually cost yourself more money in the long-run. Many of these heaters do not have built-in thermostats that are accurate.
These old heaters will still be running and heating your greenhouse when they don’t need to be. This will cost you extra, whereas a newer heater will be more accurate.
I also enjoy having my heater connect to my phone so I can adjust the heating power. Most of the time I can simply forget about my heater because it has the built-in thermostat and regulates itself.
Can I grow plants in my greenhouse all winter
I made the mistake of thinking that I could use my small greenhouse all through the winter months. I quickly learned that the type of greenhouse I have could only be used April (maybe March) through November.
I am sure that I could extend my greenhouse growing season further, but I don’t want to put that much energy into heating my greenhouse.
I also live in a very cold climate with cold winter temperatures that are not suitable for growing plants. You can, however, extend the growing season in your greenhouse by planting cold weather crops.
Here are some great cold weather crops that you can plant in your greenhouse to get the best use out of it.
If you are really wanting to extend your growing season, there are other methods (like cold frames) that are less expensive than greenhouses.
What is a passive solar greenhouse
Passive solar greenhouses use the sunlight as their primary heat source. Greenhouses that use passive solar heat to keep warm are usually buried into the soil to hold onto the day’s warmth.
If your greenhouse is buried into the ground a little, you may find it easier to sustain the heat. In fact, you can build an ancient walipini greenhouse that holds onto heat better.
People will even grow lemon trees in the middle of the winter in these passive solar greenhouses. These greenhouses are usually a larger investment and take more work than hobby greenhouses, but they don’t require heating.
How to offset the price of heating a greenhouse
Having a hobby greenhouse is really fun, although it can be pricey. There are many creative ways you can offset the price of your hobby greenhouse, and even make a profit from it.
Sell plants
A great way to make money from your small greenhouse is to start extra plants and sell them. I always start extra pepper and tomato plants just to share with friends and family.
If you want to make money from these plants you could sell them to neighbors, at a farmers market, or at roadside stands. Remember rare and unusual varieties can be sold at a higher price.
Sell compost
If you live in a northern climate, you will find that it is hard to make compost in the middle of winter. With a greenhouse you can make compost all through the winter.
Selling high quality compost from your greenhouse or just using it for your plants is a great way to offset the price of heating your greenhouse.
Sell worms
You can start your own little worm farm in your greenhouse to eat your kitchen scraps. You can then sell these worms for fishing or composting.
You can also sell or use the worm castings that these worms make. Worm castings are one of the best fertilizers for your garden.
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