How To Keep A Greenhouse Warm In Winter

Greenhouses are a great way to enjoy fresh produce year-round. They also provide a safe environment for plants to grow. Unfortunately, they don’t always stay warm enough during the colder months.

Greenhouse heating systems come in two types: passive and active. Passive systems rely on natural convection currents to circulate air through the greenhouse.

Active systems use fans or pumps to move heated air throughout the structure. Depending on the type of system used, it may be more efficient than using a window unit.

In addition, there are several different ways to heat greenhouses. For example, you can install heaters directly around the outside walls; mount them inside the glass wall (which is often a better option), or hang a heater near one side of the glass.

When choosing which method to go with, consider your budget and the temperature requirements that you have when building. 

The location of the heating device will also influence where you need to position vents to prevent carbon monoxide buildup.

If you’re planning on adding a new heating system, read these tips before buying anything. There are some easy, inexpensive ways to keep your greenhouse warm in the winter.

Tips For Heating A Greenhouse

So how do you heat your greenhouse? Well, let’s take a look at some of our tips to see what you can do! 

1. Know What You Want

Greenhouses are usually installed with either electric or propane heaters. Electric models require no wiring and allow you to connect outlets as needed or add additional ones to meet your needs.

Propane requires special connections. It comes in tanks that vary between 8 gallons and 60 gallons. A lot depends on how much space you have available.

2. Check Energy Efficiency Cost

You will also want to consider what the most cost-effective energy is! Usually, electricity, gas, and propane units are energy efficient. If you’re installing an electrical model, make sure it has an R-value of at least 4.

If you want to purchase an alternative fuel model, choose one rated at 15 watts and above. These units have less chance to burn out if a problem arises.

4 propane tanks, which could be expensive to maintain heat in a greenhouse

3. Make Sure Your System Is Right

If using a propane heater, check to see what size fuel tank you need. This will help determine whether you should replace your current heater completely or just upgrade capacity without replacing the entire system. 

Also, look into the number of hours needed to run the heater each day. Smaller models typically operate for fewer hours per day but cost less money. Larger units tend to run 24/7. However, they cost more because extra power must be supplied from another source. 

Additionally, make sure the vent hoods attached to the heater are designed to take moisture away from the area surrounding the greenhouse. Otherwise, condensation build-up could cause mold growth that leads to health problems.

4. Consider Installing An Insulated Vent Hood

Most greenhouses lose about 10 percent of their energy through ventilation. To maximize this lost energy, cover any unused openings around the perimeter of the canopy area.

Add insulation to some vents and close others completely. Insulated vent hoods are available that fit over existing vents and keep hot air away from the room.

5. Know The Temperature Requirements Of Your Plants

Be mindful about what season your crops enter the greenhouse. Selecting heaters based on seasonal requirements only makes sense if you plan on having crops for all 12 months. 

In other words, if you plant tomatoes in April, place a heater to direct hot air toward the south-facing windows so they don’t get too cold while waiting for planting time. Keep in mind that certain plants like lettuce may not tolerate temperatures below 45ºF. 

Therefore, plan to ensure they receive sufficient warmth throughout the growing cycle.

6. Choose Proper Heating Device Material And Size

Metal or ceramic heating elements work best in most cases. They’re easy to clean and maintain. However, metal can rust or tarnish over time. Ceramic tends to last longer than its counterpart. Some types of ceramic are nontoxic (like PEX-brand). Others contain lead and cadmium.

Look closely at the materials used in making the unit to avoid getting exposed to dangerous chemicals. Finally, pay attention to how the unit is made. Manufacturers use different methods such as welding, soldering, and machining.

7. Use An Air Filter

Cleanliness is important when dealing with heating devices. It’s also important to maintain a safe breathing environment in a greenhouse.

When buying a new unit, look for one that includes built-in filters. These small filters catch dust particles before allowing them to penetrate deeper into the heater.

8. Monitor Heat Output

While keeping track of temperature can be tricky, you can do it by observing how quickly air circulates within the greenhouse. After adding the heater, wait 5 minutes to 1 hour before taking careful note of the flow of air. 

Then measure it again every couple of days until plants start appearing in the area where the heater is directed. That way, you’ll know if your current setup works well or needs improvement. For example, increase or decrease the wattage of the device accordingly.

is a greenhouse heater necessary?
Photo by Achudh Krishna on Unsplash

9. Install Lighting If Needed

Since many growers decide between using natural sunlight versus artificial light, it’s vital to consider both options carefully before installing the heating equipment.

This is especially true if you live in an urban environment. You might find yourself facing harsh winds in the summer and harsh snow cover in the winter

Choosing lighting systems that work together with the heating equipment ensures you can grow even more productive during these times. There are several ways to manage heat and light. For instance, you can install bulbs that are controlled by timers. 

Or you can purchase fixtures that include special lenses that adjust brightness according to daylight hours. Either option will work effectively if you place the heater near enough to a window.

10. Be Prepared In Case Something Goes Wrong

One thing we know for certain is that life happens. We’ve all faced situations where our attempts to grow produce were thwarted by something unexpected—like a flood, a broken boiler, or a fire.

Whether you use a heated greenhouse or not, it’s always wise to be prepared in case something goes wrong. 

This means learning how to fix problems, knowing when to call in professional help, and having emergency funds available just in case disaster strikes.

A Useful Video on Maintaining a Warm Greenhouse


Hopefully, this article has helped provide useful information about greenhouse heating equipment. The choice of heating system depends largely on what type of greenhouse you have.

But regardless of size, there’s a good chance you’ll need to consider some of the issues discussed above before deciding which heater will work better.