Starting at very cheap solutions and heading up in price, we’re bringing you ways to keep your greenhouse heated over the coming colder months. If you’re a keen gardener, you’ll be thinking of how the fruits (and vegetables) of your labour will cope. Consider first, what should remain inside the greenhouse – very tender plants may benefit from being brought into the house. A greenhouse as is will provide minimal protection – It’s designed to let as much warmth in as possible over summer, and will therefore let out heat during winter. We’ve put together some methods for greenhouse heating – it doesn’t have to cost a fortune so long as you’re prepared to take a little time to put appropriate measures into place.
1. Wrap it up
Layering the inside of your greenhouse with horticultural bubble wrap will create insulation, helping to keep your greenhouse warm. Horticultural bubble wrap is UV stabilized, with larger bubbles to let in more light. As well as attaching it to the walls of your greenhouse, it can also be wrapped around pots, and placed underneath them to protect them from the frost.
As well as bubble wrap, horticultural fleece can also be used. At night, layer your greenhouse with fleece, and remove it in the morning, to allow for light and ventilation. Vents should also be opened on occasion to prevent moisture and humidity spreading disease.
2. Thermal mass
A sustainable way to operate your greenhouse during colder months is to harness the energy given off by the sun in the day time, and use this to keep it warm during the night. A cheap way to do this is by using thermal mass in the form of a heat sink. Various materials can be used for this, but water is good as it holds double the amount of heat that concrete does, and four times more than soil. You can decide how to set up your heat sink:
- Water barrels: Put a few large barrels or containers of water into your greenhouse where they’ll be hit by direct sunlight. Put more tender plants (seedling trays or warm weather crops) close to the barrel.
- Stone or concrete: Build this into the floor or sides of your greenhouse.
- Raise soil beds.
Thermal mass is easy to add, as well as being very cheap. It takes a little longer to work, and will not be as effective as other larger forms of heating systems, but it’s a great addition nonetheless.
3. Rocket Mass Heater
This method combines thermal heat with combustion to intensify its effects. It can be put together in a number of ways, using different materials, but the general principles remain the same. You’ll need a feed chamber – a space to load fuel, and thermal mass – insulated so that it doesn’t burn. The heat will be absorbed by the thermal mass, and then radiated outwards for much longer than simply the fuel burning time.
4. Climate Battery
Although this seems like a little more fuss, other than digging it is a relatively easy installation, and required little maintenance. It provides a significantly large heating system, along with relative control over temperatures.
It works by installing tubes underground. There are usually two sets of tubes, one 2″ and one 4″ below the surface, filled with water. Fans are installed in the greenhouse, and during the day, they push warm air down into the tubes which warms the water. In the night, the temperature falls and the water droplets condense. In this change of states, energy is released in the form of heat. This warms the soil, and by extension, the greenhouse.
As this system is so large, it provides a significant heating system for the plants inside your greenhouse. Fans mean that the air is distributed more evenly around the greenhouse, preventing pockets of cold air. You can also have a degree of control over the system by installing fans connected to a thermostat. This way, you can make the heating system start up and stop at certain temperatures.
5. Electric Heater System
Electrical fan heaters can be used if you have a mains power supply to your greenhouse. These have the added benefit of pushing the air around to distribute the warm air evenly. Alternatively, without a mains supply, you can use a paraffin heater, although these should be operated with great care. An eco-friendly and more sustainable solution involves solar panels, some of which can be found cheaply, and placed on the floors or walls of your greenhouse.
Take some time to decide what temperature your greenhouse needs to be – most tender plants can get by with a minimum temperature of 7°C. The position of your heater is important. It should be away from any sources of water, and shouldn’t be blowing hot air directly over plants foliage.
Heating a greenhouse this way can be a little costly, so only heat the areas that need it. Putting in dividers can make the most effective use of your heater. You will also need to be very careful with ventilation, as added humidity and moisture can spread fungal disease. Plants should be watered only when they need it, and early on in the day. Open the vents of your greenhouse on warm mornings and close them before night falls.
We hope this helps you with your greenhouse heating. Taking a little time to care for your plants will help them stay cosy (and hopefully, alive!) through the colder months. Can’t get to your greenhouse for leaves? Lucky for you, we’ve put together an entire guide for how best to deal with stray leaves. Missing the greenery? Bring it to you with this indoor vertical planter DIY.