Does a Greenhouse Need a Heater: Gardening Solutions

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For the every-day gardener, the idea of hanging up the trowel and putting up the work gloves means missing out on the simple pleasures of ushering in new plant life for the wintery season. Keeping our sproutlings warm in the winter has become a question each budding agriculturalist must answer for themselves; should we add heat to our greenhouses? How much is too much?

Do greenhouses need a heater? The need for a heater in a greenhouse is totally dependent on where you live, the plants you’re looking to sow, and the outcome you intend to have. Heat promotes growth, and is equally as important as light and water. Heaters can offer some great perks to even the most established farmer.

Luckily for us, the production and availability of indoor and outdoor greenhouses have boomed in the last few decades, leading to year-round sprouts and the potential to grow even more. Streamlined misting, germination stations and advancing growth plans make it so even beginners can enjoy the process without having to stress about the finer details. With these bigger and better setups coming into public view each year, backyard agriculturalist interest is all about efficiency, affordability, and often features the classic “do I really need it?” question.

Now, more than ever, the opportunity to grow food, flowers, and medicinal herbs continues to inspire backyard gardens and leafy family projects. With new and greener pastures, however, comes those bigger and greater challenges. Space management, water systems, ventilation requirements and more are all at the forefront of conversation as absolute must-haves for even the most basic of greenhouse setups. Among them, temperature management is still a constant talking point for many.

In general, natural heat is the go-to, tried and true solution for the most basic of greenhouse setups. Added and artificial heating can promote further production through the winter months, but a well insulated cultivation should be enough to get most folks by with little issue. There are many factors that come into play when answering this question, including locale, the kind of plants being tended to, and the expectation of production for those plants. Chilly plants might not die, but they might not want to pop out those extra peppers either.

Knowing your region, your skill level, the materials you already have and the outcome you are trying to produce can help with these difficult and sometimes overwhelming choices.

If you are looking to grow sun-loving plants, fruit, vegetables, or herbs then a constant temperature will be needed. This can be achieved through direct sunlight and an automatic ventilation system or by choosing the best heater for your greenhouse, just make sure you pick a heater that has the power output to heat your sized greenhouse.

Is a Greenhouse Heater right for you?

The answer could depend on which of the zones in which you intend to grow. In the United States, regions are divided into 13 major Zones based on minimum temperature, with Zone 1 being the coldest and 13 being the warmest. Zones 1 through 4 can reach temperatures as low as -50 degrees Fahrenheit and up, which makes for some pretty frosty foliage.

In cases like these, many at-home farmers are looking to sustainable and effective solutions for their temperature woes by means of electric, wood, gas, and industrial heaters.

Zones 8 through 13 can experience overheating in the spring and summer, causing a decrease in plant production and growth. Warmer climates and even more temperate ones can feasibly sustain a working and fully insulated greenhouse which would render a heater obsolete, or even dangerous to our little green friends. Though plants do need heat to survive, too much of a good thing can always lead to a bad one. In zones like these, composting, insulation, and coverings can make a big difference to your plants without the additional costs and stressors of a managed heating system.

Keeping in mind that a greenhouse is a mirco-climate all its own, fully managed by you.  It’s important to research what plants you intend on growing to know the overall heat requirements they are going to need to really thrive. Once you have that, applying what you know about your area and the heat management methods you already have in place can help you make the leap one way or another.

If you are growing fruits, vegetables, herbs, or plants that thrive in a heated environment then you will probably need to consider a greenhouse heater, especially if you are looking to grow over the winter months. I reviewed my top 5 best heaters for greenhouses for all sized greenhouses – so if you are thinking about getting one then it’s worth checking out.

So How Many Kinds of Heaters Are There Really?

On the market right now, there are dozens of efficient heaters to choose from, all with their own requirements and perks. Doing your research on your plants and knowing what your desired outcome is will help you make a choice based on your and your sproutlings needs.

types of greenhouse heaters
  • Paraffin Heaters-  Paraffin heaters are an affordable go-to for the avid traditionalist. They offer reservoirs that allow them to run without constant maintenance and don’t typically require a source of electricity.  Sizes vary to allow for different requirements to be met based on the greenhouse type. Unfortunately, the fuel isn’t as common as it was back in the day, which means the cost for running them may outweigh the affordability of the unit depending on your area. Paraffin heaters also emit water as they run, which can promote mold and excess moisture in the greenhouse, but can add much-needed humidity to the right set of plants.
  • Electric Heaters- Electric heaters seem to be the most common aside from the more natural heating methods. These units tend to be reliable as long as they have power, and can be paired with more renewable sources of energy such as solar or wind. Most workshop and greenhouse electric heaters have fans included, which allows for consistent air circulation. It goes without saying that these kinds of heaters need to be plugged in, so proximity to an outlet is of the utmost importance with these. Knowing the wattage, the output, and the pricing can all be factors of choosing an electric heater fits best for your setup. Electric heaters can be a little pricey, but with the added potential of a connected thermostat, these little guys can offer a more hands-off heating approach.
  • Propane and Gas Heaters- RIght off the bat and much like woodstove heaters, these heaters offer convenience separate from a connected outlet. Burning propane and gas produces and encourages the absorption of CO2 in your plants, encouraging growth and production. The source of fuel for these can be purchased in bottles and tanks, making it an accessible and easily attainable source of power in setups with little to no electric culpability. These machines can be a little expensive depending on the size, so having a vision for where it’s going and how it’ll be positioned might help save a few bucks upon purchase. All in all, these are stable and safe heating options.
  • Wood and Coal Heaters- The concept of a wood stove in a greenhouse can seem a little off the wall on first glance. With these heating systems, a more monitored approach is generally recommended and the heat can be inconsistent without proper fire maintenance since once the fire dies, the heat dissipates quickly. Meant to be used in well-insulated and well-maintained enclosures, these heaters provide a natural bug and pest repellent by means of the smoke produced. The wood and coal ash contain potassium and lime, which is an excellent additive to any fertilizer. These systems are easy to DIY and with enough attention, love, and care, they can add a little fire to your gardening experience.

Greenhouse Heating Alternatives

Based on all the factors listed above, at this point you may have decided on coming up with a more natural or self managed heating system. Though these systems are not infallible, using some or all of them can help to get you a few steps closer to a toasty greenhouse set up, even when it’s frigid outside. In most, if not all of these systems, a hearty insulation setup is highly recommended for heat retention once it’s gathered. Generating heat is one thing, but keeping it in a way that’s useful is another.

  • Heat Sinks- Commonly known as thermal masses, heat sinks are a great way of gathering solar heat using a tank of water and a jug. Typically, the tank of water is approximately 55 gallons, and the jug can be as simple as a painted milk container. This works when the jug is painted black and therefore absorbs the heat, and much like a swimming pool in the summer, the water’s temperature rises over time. At night, the heat is still retained and is released as the outside temperature drops. This cycle repeats as long as there is solar heat during the day.
  • Composting-  Compost heating systems, also known as Biomeilers, heavily rely on composting as a means of generating heat energy. Composting is a beneficial way of reducing waste while repurposing that energy for growth. This generally works as a DIY project that includes a wooden or plastic box with a means of closing. Based on a general composting consensus, a sure-fire way to begin a fully functional compost bin is to combine two parts of a “brown” component, which may include wood chips, newspaper, sawdust, and/or dry leaves with one part “green” component (ie discarded veggies, grass clippings, coffee grounds, etc.) and water. As the concoction breaks down, heat is released and can be reused if harvested correctly. Many at-home gardeners stack compost between rows of plants to evenly distribute the warmth, though it should be mentioned that as the components break down, the release of heat will slow over time. Keeping a constant temperature will mean a renewal of the compost as the materials decompose, which can be a little more hands-on in comparison with other systems.
  • Radiant Floor Heating- While technically this method does include an external heat source like a boiler, this means of heating a greenhouse can be considered alternative as well as it can be paired with any other method on the alternative list. This process includes running pipelines beneath the floor filled with warmed water. This heats the pipes, which warms the ground. It can be an expensive way to go upon installation, but one that will last years if done correctly. There are also a ton of DIY opportunities for the particularly savvy with this one, and offers a mostly automated means of heat generation.
  • Solar Energy Farming- Clean energy is a huge selling point for many of today’s avid farmers. Using solar panels, one can power an electric heater on the inside of the greenhouse, allowing for all of the perks that come with the electric heater, minus the costs of power. Start-up on solar can be a pretty penny up front, but also has the potential to pay for itself over time. Solar in general can be used without an additive, so long as the area allows for direct sunlight into the enclosure.
  • Wind Power- Much larger than most backyard planters have the time or space for, wind-powered turbines are a great source of renewable power for larger setups. Having the option for harvesting wind energy means a little bit of an investment up front, a wide-open space for these to work to their full potential, and basic maintenance. Definitely not for the faint of heart, or recommended for beginners!

Adding Heating Add-Ons vs Small Alterations

Having a good base to start on has to be one of the biggest recommendations any backyard farmer can make for a new enthusiast.

The position of the greenhouse is of the utmost importance. Choosing a location where the structure receives as much sun as possible will help with just about everything involved in growing from home. Generally speaking, the sides of the enclosure should reflect the direction of the sun. North and South sides of the enclosure can and should have additional insulation to trap heat, whereas the East and West sides should include windows allowing the sun in.

General pre-made greenhouse kits allow for hopeful planters to throw up an enclosure in the matter of a few hours, all ranging in size and materials. Those who choose to build from scratch have more personalization options, which leave room for more consideration in the long run. When building a greenhouse, of course it’s important to be sure to be mindful of the materials used, how well they absorb and retain heat, and how easy it will be to replace them when needed. An example of this would be frosted glass or thick plastics for windows and roofs as they allow sunlight to peek through without damaging the plants. 

Insulation is key to any structure focused on heat retention and even distribution of that heat. Something as simple as adding another layer to the outside of the greenhouse can make it that much harder for heat to escape. Everyday materials like tarps, and bubble wrap can be used to insulate your setup  from the inside as well, since the bubbles of air can catch and hold heat. Horticulture bubble wrap is preferred in these situations, as the air bubbles are much bigger than regular packing materials.

It’s important to only heat what you actively need to, which means that if one season’s harvest only takes up half of your setup, heating only half and blocking off the rest until you’re ready to use that space can cut worry time in half. Use sheets of plastic, large tarps, or cinder blocks to insulate the space as needed, and watch your heating needs become much less of an issue over time. The smaller the space, the less heat needed to keep it warm.

Caulking corners and sides to ensure nothing is leaking and keeping the door closed when it’s not in use can work wonders on heat regulation!

All in All, Is Purchasing a Heating System Worth It?

Year round agriculture is complicated for most and a long struggle for some. If you are in a part of the United States that is known to struggle with temperature fluctuation, low temperatures for long periods of time, or have a history of a low yield in your plants, an added heating system might be a good fit for you.

It’s all about what your plants need to survive and thrive in the environment they’re in, while producing the outcome you hope for. It’s important to look into possible restrictions of your area and whether or not your current setup can be changed for the better. Smaller and less intensive alterations can not only save you the time and money it takes to install, but also the headache of correcting an ill-fitting system later down the line.

No matter what method you choose, backyard gardening can be a very forgiving past time. Trial and error, making adjustments and trying again are sure fire ways to find what works for you and your sprouts. As time goes on, it’s likely new and improved ways of planting and managing from home will be developed, and being open to new things can make an already great sprouting season that much sweeter.

Innovation and stick-to-it-iveness can offer the best practical lessons for you and your plants, though finding a community in your area with similar interests and experiences may help too!

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