Ways to Heat Your Greenhouse in the Winter

Here in Wyoming, winters can be brutally cold and crazy windy, so choosing the right greenhouse was pretty important. When we started our search, we discovered that there are so many options, and it was easy to feel overwhelmed.

Even though we have cold, snowy, windy Wyoming winters, we still chose to go with an unheated greenhouse. It wasn’t an easy decision, and all the choices did overwhelm us at first. In the end, we found The Greenhouse Mega Store and they were able to point us in the right direction.

If you are struggling with all the options or have a ton of questions about which greenhouse you should get, give their customer service a call. The Greenhouse Mega Store should be able to help you with all your greenhouse needs.

You can also listen to  How to Use a Greenhouse for Increased Food Security from the my Old Fashioned on Purpose Podcast, to hear firsthand from their marketing director. So far, the greenhouse we bought from them (one of the Gable series models) has done a great job against our strong Wyoming winds. 

If you want to learn how to cool your greenhouse in the summer, check out my article here —> Ways to Cool Your Greenhouse in the Summer

What is a Heated or Unheated Greenhouse?

When people talk about choosing a heated greenhouse, it simply means that they have a greenhouse that contains heat and air circulatory systems installed. While it sounds nice to be able to control the heat, it may not be cost-effective for a home gardener.

An unheated greenhouse is a structure that is designed to use sunlight as its main source of heat. The sun comes through glass or plastic and warms the air inside the greenhouse. Sunlight combined with other methods of heating can be an effective way to heat your greenhouse without extra cost.

Don’t think like a heated greenhouse is your only option just because it gets below freezing where you live. If you opted out of buying a heated greenhouse like us, then you will simply need to find a different way to produce heat during those cold winter months.

Luckily, there are different ways to heat a greenhouse during winter, and having an unheated greenhouse ourselves has given us the opportunity to try out a few to share.

Ways to Heat Your Greenhouse During the Winter

1. Heating Your Greenhouse with Sunshine

A greenhouse is designed to allow sunlight in and trap the heat that is produced. During the day when the sun is out, you can rely on the heat produced by the sun to help heat your greenhouse.

The problem is those daylight hours are shorter in the winter. Plus, you have to think about nighttime. Not only is it colder at night, but the sunlight isn’t available to help you heat the greenhouse.  During the night, an unheated greenhouse will drastically lower in temperature to meet the temperatures of the outdoors. Unless you live in a mild climate, you will need to combine another method of heating your greenhouse with this one.

2. Using a Compost Pile to Heat Your Greenhouse 

Making and Using Compost can help heat your greenhouse and is a great way to prevent organic materials from going to waste. Compost is made through the process of decomposing organic material. During this decomposition process, your compost pile generates heat. If you place a compost pile in your greenhouse, then the heat produced in that compost can help raise the air temperature. 

Note: The amount of heat produced depends on the size of your compost pile, the amount of moisture it contains, and the surrounding air temperature.

3. Using Thermal Mass Objects to Heat Your Greenhouse

Thermal mass objects have the ability to absorb, store, and radiant heat. They are a great cost-effective way to heat a greenhouse. 

The most common thermal mass object used in greenhouse heating is water. Drums can be painted black, placed in direct sunlight areas, and filled with water. This water thermal mass method is also known as a heat sink.

We don’t use large water drums (yet), but I do fill old plastic milk cartons with water and place them around my plants during the winter. The water in the containers hold heat longer into the night, and the plants nearby benefit from this.

Another way to store heat for your greenhouse is by using bricked pathways or just simply adding bricks or stones to your greenhouse. Bricks and stones hold heat and can help naturally and gently heat up your greenhouse during the night. This isn’t going to dramatically warm up your greenhouse, but every little bit you can do can help. I’ve heard of some folks putting large stones in the middle of the greenhouse garden beds because they can help warm up any plants that are planted right next to them.

We are halfway finished with the process of making all of the pathways out of brick and I’m excited to see if that makes a difference in there during the upcoming winter months.

4. Use Small Animals to Heat Your Greenhouse in Winter

Small animals like chickens and rabbits have been used for years to help keep greenhouses warmer during the winter. This method of greenhouse heating is also known as bio-heating. Chickens and rabbits create body heat and manure that can be composted to warm the air in the greenhouse. An added bonus is that these animals also produce carbon dioxide which is essential in the growth of plants. 

Note: If you are using small animals to help heat your greenhouse, you will need to provide coops or runs to prevent damage to your plants. 

5. Insulating the Walls of Your Greenhouse

The Winter months can be very cold, so to help keep the heat inside, you can use a layer of  “bubble wrap” (Bubble Polythene) to trap the heat. Bubble polythene is available in sheets that you can attach to the walls of your greenhouse.  This bubble wrap is clear so it allows the sunlight in, traps the heat produced, and keeps drafty air out. 

Of course, you can try other creative ways to insulate your greenhouse walls if you cannot afford (or find) bubble polythene. Our version, for example, has been to store hay bales along the outside walls on the sides of the greenhouse that get hammered by our winter winds. It has helped keep the temps more stable in our greenhouse.

6. Use the Hotbed Method to Help Heat Your Greenhouse

The hotbed is when the composting method is used under topsoil in your garden rows or raised beds. Composted materials are left to decompose under about 6 inches of topsoil in the rows where you have planted your plants. The materials will continue to decompose creating heat that will keep the roots warm and warm air that rises.

7. Insulate Your Soil to Help Heat Your Greenhouse

Soil is its own thermal mass object, it absorbs heat that is provided by the sun or another outside source. To keep the soil from losing the heat it has absorbed, you can use a mulch to insulate it. Mulch can include straw, grass clippings, wood chips, and dead leaves. This method helps heat and also adds organic materials to your soil.

8. Cover Your Plants to Help Keep in the Heat

Like mulching, a cover can help keep the heat from escaping into the air. A cover sheet is usually used because it allows sunlight in and keeps the trapped underneath. Row covers can be used to cover larger areas, but another smaller DIY option is milk jugs or clear plastic totes. 

We started covering our greenhouse plants with row covers last winter and it helped a TON to keep the plants alive during brutally cold nights. As long as I remember to cover them in the evening and remove the row covers in the morning, the plants are pretty happy (it can get pretty warm in the greenhouse during a sunshine-filled winter day and I have killed a few plants from wilt/heat by forgetting to remove the row cover during the day).

9. Greenhouse Geothermal Heating

Geothermal heating is essentially heat produced from the ground. Water or air goes through tubes that are under your greenhouse. While it is moving through these tubes it is being heated by the soil.  We took a field trip to an amazing greenhouse that has been heated with geothermal heat, you can watch our experience here.

 

We are thinking about adding geothermal heating to our greenhouse in the future. However, it would have been MUCH easier to add this feature before we built the greenhouse, so if this is something that interests you, try to remember to add that feature at the beginning of your greenhouse construction if you can.

10. Using Heaters in Your Greenhouse

Electric heaters are kind of an obvious way to heat your greenhouse. An electric fan heater or two can be placed in your greenhouse as long as you have a power source available. Electric heaters are usually equipped with a built-in thermostat that can regulate the temperature. You can find electric heaters that are made for heating greenhouses but keep in mind the area size you are trying to heat. 

Some folks put woodstoves in their greenhouses, which sounds pretty darn awesome to me. We haven’t done that (yet), but that is an excellent option for a great heat source if you have access to wood and you have a decent-sized greenhouse that can comfortably fit a woodstove.

Another Option for Winter Gardening…

If you are worried about the amount of heat that you will be able to provide or about the expense of a greenhouse, another option is to simply extend your growing season and also try growing cold-loving plants.

There are a ton of different vegetable options out there that you can plant in the fall for a winter harvest. Planting these will limit the amount of heat that you will need in your greenhouse (and you might be able to grow an extended fall garden outdoors without a greenhouse at all). For a list of vegetables and how to extend your growing season take a look at How To Plan Out Your Fall Garden.

And listen in to my podcast episode: The Mysterious Winter Garden Podcast Episode

Start Heating Your Greenhouse in the Winter

Use one of these methods or combine them all, these are great ways to heat your greenhouse without a huge expense. Planting cold hardy plants, starting a compost pile, or housing chickens in your greenhouse are simple ways to add a little heat during those cold winter days. It’s going to take some trial and error to figure out exactly how many ways you need to add heat to your greenhouse in order to keep your plants thriving. So keep good notes, keep checking the air and soil temperatures in your greenhouse, and observe the vitality of your plants to see how you’re doing. 

Do you have a greenhouse that you heat in the winter? Are there any methods that work best for you?

Don’t forget to check out my other article here —> How to Cool Your Greenhouse In The Summer

More About Growing Your Own Food:

• How to Manage Your Garden Harvest (Without Losing Your Mind)
• How to Extend Your Garden Season
• Fast Growing Vegetables to Grow for an Early Harvest
• How to Plant Garlic
• How to Grow Your Best Onion Crop Ever
• How to Garden in a Cold Climate