▷ DIY Guide to Heating a Greenhouse (2018 Update)

DIY Guide to Heating a Greenhouse

Written by Joseph Biggs and updated on October 25, 2018
Heating a greenhouse

You probably purchased your greenhouse with the intention of extending your growing season, but are wondering what you need to do when it comes to heating a greenhouse to achieve that goal. You want to be able to start your seedlings earlier in the winter without cluttering up your home or keep your container plants growing well after fall hits your region. Your greenhouse can accomplish these tasks.

Ideal Greenhouse Temperatures

One of the first things to keep in mind is temperature. The type of plants that you're keeping in your greenhouse will help you determine how warm you need to keep it. For instance, if most of the plants you’re growing are rather hardy, you’re able to keep it at about 36 degrees Fahrenheit.

Plants that are tender, especially seedlings, require a temperature of around 45 degrees Fahrenheit. Tropical plants will need to be kept at about 55 degrees Fahrenheit. Keeping a thermometer in your greenhouse will be helpful when it comes time to make sure that your greenhouse is at the temperature you need it to be for your particular plants. This is a dynamic process, so it's best to use remote sensors to manage the heating and cooling of your greenhouse. This is both for the health of the plants and for your convenience. 

You may decide that you want to keep it at the cooler temperature range but still plant seedlings. One way to accomplish this would be by adding a heated seed mat or heated propagator to your greenhouse. This extra heat source can make a world of difference for your delicate seedlings.

Depending on your area, you may be able just to use insulation to get your greenhouse to the 36-degree mark, but that may not be an option for all growers. You may want to look into what a solar-powered greenhouse can offer. Solar power is a great option because it uses a renewable, natural resource to power your heater. A bonus of solar is not having to worry about issues that come from needing electricity for your greenhouse.

Your home energy bills will thank you, and you won’t have to worry about how you’re going to get power out to a separate structure in your yard. If you think about it, your greenhouse is already a solar-powered building since the construction is of a clear material to focus the light into the room to help grow your plants. It just may need some additional assistance when the colder months arrive.

Types of Greenhouse Heaters

There are active and passive solar greenhouse heating systems that you can implement for your greenhouse. These systems typically incorporate a heat mass that can absorb the heat and then give it off to the surrounding area. Most systems will use rocks or water for the heat mass.

A passive system means that there is nothing electrical going on with the system - it acts in a natural manner. An active system is one where pumps, blowers, and fans are incorporated to help spread the heat. The type of system that you have installed will depend on your greenhouse’s size and what you’re looking to grow inside of it.

The type of glazing you use can also play a role in the amount of heat generated by your greenhouse. You may want to evaluate if your current panels are contributing to heat loss during the cold weather. Corrugated, high-density polyethylene is one of the best glazing types for your greenhouse panels. There are a variety of other materials available on the market that can work for a greenhouse.

Some people find that using recycled materials can be a great way to save money and have replacement parts on hand. For instance, glass can be a good choice for your greenhouse, but it can be fragile and may not be up to withstanding snow. If it breaks, you just need to find another recycled piece that fits.

Greenhouse Ventilation

Ventilation is a topic that you want to think about when heating your greenhouse. You’re probably aware that ventilation is essential in the warmer months when the greenhouse effect is known to occur and the temperature rises within the environment. Proper ventilation is also necessary when you’re running a heater because you have to deal with the humidity that will be in the air.

This can cause condensation to gather on your greenhouse panels and be a regular nuisance. Stale, humid air can create its own problem when it comes to pathogens, molds, and mildews. Stagnant, humid air can be the perfect breeding ground for these plant problems. Ventilation can help to prevent these from occurring in your greenhouse. It can make the difference between having to deal with fungus or molds and not having them appear at all. 

Knowing how to heat a greenhouse properly will allow you to get the most usage possible out of your greenhouse. You want your greenhouse to provide you with fresh produce throughout the year and keep your seedlings warm before you’re able to plant them. In order to accomplish this, you need to think about how you’re heating your greenhouse. A solar greenhouse heater, active or passive, can be a great way to accomplish this goal.

For a lot more great gardening tips, see our guide on 31 Ways to Make You an Organic Gardening Guru. Also, check out our related gardening gift guide.

About the author

    Joseph Biggs

    Author and retired entrepreneur Joseph Biggs writes for Organic Daily Post exclusively, when he is not spending time outdoors with his family. He, his wife, and their children and grandchildren live on an extended mini-farm where they all practice conservationism and a whole-Earth approach to life.

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