How to Heat a Greenhouse? Complete Guide

Learn how to heat a greenhouse to extend the growing season in your garden.

You may be concerned about your greenhouse’s capacity as the colder months approach. Will it be able to resist the frosts long enough to keep your crops growing through the winter?

Knowing how to heat a greenhouse is crucial if you live somewhere with cooler temperatures or want to try your hand at growing more exotic plants that require plenty of warmth. Thankfully, there are many options available.

This article will examine 7 creative methods for heating your greenhouse in the winter. But read on, because, toward the end of this article, we’ll talk about steps you can take that means you might not need to.

9 Heating Options for Your Greenhouse

The good news is that you don’t have to use limited and harmful fossil fuels to heat your greenhouse during the winter. Whether you are on the grid or off it, all of the options listed below are environmentally friendly and functional.

You might find it easier to be kind to people and the environment if you choose one of the following options (or a combination of two or more of these options). And demonstrate for you how you can grow food all year round in a cold climate while acting morally.

1. Hotbeds (Heat from Composting Materials)

Making hotbeds is one quick and easy way to keep a greenhouse at a comfortable temperature and prevent frosts.

A hotbed is essentially a raised bed that has been covered in layers of composting straw, manure, or other organic matter, with a thin layer of growing medium (soil or compost) on top. It essentially functions as a raised bed and is made from a compost heap that has been covered with soil or compost.

A hotbed is constructed out of organic materials, just like any other compost pile. A good balance of nitrogen- and carbon-rich (or “green” and “brown”) materials is ideal.

Create a Hot Bed

Would you like to give your seedlings a healthy and head start? Consider building hot beds instead of using electricity or gas to generate heat. This method dates back to the Victorian era and is more sustainable and less expensive. The heat produced by decomposing organic material is how it operates, so that’s how.

Raised beds should be prepared by compressing organic, compostable material (such as straw or manure) into them, covering it with topsoil and compost, and then covering the entire thing with soil. The ideal proportion of organic matter to growing medium is 3:1.

Sowing your crops is then possible. The heat will be increased even more if there is a cover over the top, like a small cloche. Additionally, you can dig the compost out and use it to mulch your raised garden beds outside in a few months once it has cooled and started to rot.

Cover Your Hotbed to Retain More Heat

Plants can stay toasty and warm even in the coldest environments if you cover your hotbeds with cloches or row covers inside your greenhouse. You may want to think about covering your hotbed in a number of different ways. You could use, for example:

• a cracked window pane of glass.
• A “hot box,” as they are sometimes referred to, is a glass cloche or miniature greenhouse.
• Polycarbonate sheet that has been recovered.
• Plastic greenhouses, polytunnels, or row covers are also available.

You can frequently use things that would otherwise be thrown away.

2. Hot Water Heating

By piping your greenhouse beds with a hot water pipe heating system, you can also provide soft heat from below. Hot water heating systems were also common in grand 19^th In those days, however, the water was typically heated by coal boilers, leading to century greenhouses.

Today, there are thankfully a few more eco-friendly options to take into account when heating the water for such a system.

Installing solar water heating panels is the first option, as is purchasing them. These aren’t solar power systems that produce electricity; rather, they are buildings that let the sun heat water. These are also referred to as hydronic heating.

Another interesting idea to take into account is coiling pipes inside a composting system if you want to heat water in a simpler, more low-tech manner. Heat is produced by the materials breaking down in any compost heap, including the hotbed mentioned above. Water pipes will also transfer heat and maintain higher soil temperatures if they are run through a compost heap before entering your polytunnel.

Solar water heating might be adequate in certain circumstances. In other instances, the solar water heater may be used to pre-heat water to raise its temperature before it is sent to a boiler. (Listed below are more details regarding boiler options.)

3. Try An Air Or Ground Source Heat Pump

A ground source heat pump installation is another environmentally friendly choice. Although they do need electricity to operate, they use the heat that is stored in the ground and convert it into heat that can be used in your greenhouse.

While this is going on, air source pumps use the heat from the outside air to either warm the air inside your greenhouse or the water in its pipes. Air source heat pumps are less expensive to install than ground source heat pumps because they don’t require excavation costs.

4. Renewable Electricity Heating

Utilizing renewable energy sources is a slightly more conventional method of heating your polytunnel sustainably.

Usually, this entails installing solar panels to harness solar energy. Small amounts of electricity are required to run fans or pumps for the systems mentioned above, and solar panels can supply those small amounts of power. Or, of course, to power effective heaters for greenhouses.

Generally speaking, heating the soil beneath plants is preferable to heating the entire greenhouse. So before considering space heating options, think about piping underground heating.

An effective electric boiler for such a system can be run using renewable electricity (from solar, wind, or water sources).

5. Thermal Blankets

Utilizing a thermal blanket to keep plants warm overnight can resemble tucking them in for a plant parent who takes the title of “plant parent” pretty seriously.

“It’s the same idea as when you go to bed at night and pull a blanket over yourself,” Gowdy says. “Instead of warming you, the blanket traps the heat that your body is radiating, keeping you toasty warm.”

A thermal blanket or other cloth covering for growing specimens allows for a more effective use of heat because it prevents heat from rising to the greenhouse’s ceiling where there are no plants to use it.

6. Wood-Fired/ Biomass Heating

As previously mentioned, the sun or organic matter in decay can both heat piping-hot water used to heat greenhouses. However, a boiler can be used if those methods fail to heat the water to the desired levels.

An electric boiler can be powered by renewable energy, as we’ve already discussed. However, it is also feasible to operate a boiler to heat your greenhouse using wood or other types of biomass.

With used 55-gallon drums, you could build a simple DIY system like a wood-fired boiler. It makes a lot of sense to combine greenhouse heating with a solid fuel stove in your home, if possible.

Constructing a rocket mass stove is another excellent way to heat your greenhouse with solid fuel. A rocket mass stove combines effective combustion with heat retention. Above a type of heated shelf that extends from the stove, planters can be constructed. In areas with particularly chilly winters, this is a fantastic solution.

7. Rustic Heater With Candle and Plant Pot

It might not seem worthwhile to install one of the more intricate heating systems mentioned above if your greenhouse is only a small space.

The height of simplicity is a different creative option to think about. You can make a tiny space heater that can warm a little space by setting a candle underneath a ceramic plant pot.

The usual safety precautions apply to using any naked flame, so use caution when considering this idea. However, a small greenhouse can be kept free of frost using the heat produced even by a candle.

8. Heating With Livestock

By thinking outside the box, combining the production of plants with the care of animals is another way to keep greenhouse plants warm enough in the winter. For winter growing, keeping chickens in one section of a greenhouse (or in an adjacent coop) while growing plants in another can be a smart idea.

The heat generated by the chickens’ bodies and by the heat their manure emits can build up. And can actually surprise you by significantly increasing the greenhouse’s interior temperature at night. The greenhouse will absorb heat from the sun during the day, keeping the chickens’ housing warm for them as well.

Additionally, you might keep other livestock in one area of a greenhouse while growing plants in another. Once more, the animals’ body heat can keep the plants in the greenhouse warm at night.

9. Keep It Insulated

Reduced heat loss, whether you’re using an additional heat source or not, is one of the most efficient ways to keep your greenhouse warm, regardless of whether you chose one of the best mini greenhouses or a larger design.

You should look for and patch any cracks along windows and doors. Make sure you can still open them to let air in.

After that, you can use horticultural bubble wrap to line your greenhouse and keep the cold out. To ensure that enough sunlight can still pass through, make sure to thoroughly clean the glass before choosing a style with large bubbles. Remember that some crops will suffer from less light; for example, the RHS advises against using insulation around more hardy winter lettuces and alpines.

Your tender plants and seedlings will fare better if you cover them with a layer of horticultural fleece on particularly chilly nights.

Related Reading: How To Keep A Greenhouse Warm In The Winter?

Do You Need to Heat Your Greenhouse in Winter?

Before putting your greenhouse through the process of adding additional heat, you should give this question careful thought.

Some regions don’t even require you to heat your greenhouse during the winter.

Let’s say the low during the winter is rarely below 30 degrees. If so, you can use your greenhouse to easily grow a variety of cold-tolerant vegetables through the winter and into the spring.

However, no matter how hardy your crops are, you will need to add some sort of supplemental heating if you frequently experience harsh winters with temperatures in the single digits or below.

Of course, if your goal is to use your greenhouse in the middle of January to grow warm-season vegetables, you’ll likely need to combine several of the techniques listed below to keep your plants healthy and productive. Even if your area has a more temperate climate, this is still true.

Also Check: How Does A Greenhouse Work?

Factors to Consider

As a result, you now have choices. However, how do you decide? While it’s important to consider personal preference, the following factors will enable you to make a decision that is truly unbiased.

Operation Costs

The majority of hobby gardeners are constrained by their available funds; I know I am. The first step in selecting a system or piece of equipment to keep your greenhouse warm is determining how much money you can and are willing to spend.

Whether it’s on a spreadsheet, in your gardening journal, or with one of those old-school printing calculators, simply add up what you’re thinking of buying until you reach your allotted amount of moolah.

If your budget is exceeded, you will need to select a less expensive heating option.

Depending on the heating system you choose, remodeling an existing greenhouse might be less expensive than starting from scratch.

Here are some common greenhouse heating fuels for your consideration, listed from least expensive to most expensive per unit of heat produced: natural gas, wood, propane, heating oil, and electricity.

You should also take into account the local resource and utility costs, as well as the installation fees for any items you can’t set up yourself.

Related Reading: How Much Does A Greenhouse Cost?

Greenhouse Size

Greater heat loss and greater heat requirements are associated with larger greenhouses.

While a hobbyist with a backyard hothouse the size of a shed might be able to get by with the sun and a single heater, a glasshouse designed for commercial production will almost certainly need something bigger, more powerful, and more complicated to maintain the same level of warmth.

The design of the roof has a significant impact on calculating the interior volume of an existing greenhouse. In order to calculate the volume of a rectangle-shaped structure, a simple equation is to multiply the width, length, and height together. The roof section’s volume will then need to be taken into account.

Verify again the dimensions of your heating systems and the amount of space required for their operation.

Heat Requirements

This largely depends on where you put your greenhouse, what growing zone you’re in, and what you intend to grow inside of it. A greenhouse in Florida is going to need less heating than one in Minnesota for example

British thermal units (Btu) are the units used in the greenhouse industry to measure the amount of heat needed to raise a pound of water’s temperature by one degree Fahrenheit.

Btus is a common unit of measurement used to describe output in systems and products. Using this measurement, you can determine which types of heating will best suit your needs based on the size and volume of your setup.

Maintenance Requirements

It’s not difficult to leave a stack of bricks in your glasshouse to serve as thermal mass objects. A bit more challenging is repairing a broken boiler or setting up a system of pipes.

Not to mention more expensive, if you lack the knowledge to set up or perform the required repairs yourself.

Fortunately, you can always hire out for installation and repair services; however, this adds yet another expense to take into account.

People who pride themselves on being independent, especially those who live in remote areas, might benefit from picking a heating system that they can install and maintain themselves.

Anyhow, before making a purchase, make sure to review any warranty details and guarantees.

The last thing you need is financial difficulties if these components malfunction on you.

Sustainability

Your eco-conscience may be troubled by the thought of all that manufactured trash and fuel consumption.

People who care about the environment might choose efficient systems powered by clean energy over a more traditional or perhaps more practical form of warming.

Gowdy also mentioned wood as a solid choice in terms of “clean” fuel for a boiler, “as long as you have access to the wood, and you’re willing to get up in the middle of the night to make sure that it’s working and it’s got fuel.”

In the end, you must weigh your options based on what is readily available to you and how much of an impact it has on the environment.

FAQs

The Bottom Line

Hopefully, you now have a good understanding of how greenhouses maintain their temperature as well as some suggestions for heating your own hothouse.

Plants can be grown in a greenhouse in regions or during seasons where they wouldn’t thrive outdoors because of the weather and climate there.

Read More: Types of Greenhouse