How To Keep a Greenhouse Warm In The Winter

If you love growing your own fresh vegetables and flowers, you may have thought about how to keep a greenhouse warm in the winter. Owning a greenhouse might imply that the frigid winter will no longer truncate your cultivation season. Winter nights can be cold and long, So how can you save the plants with proper greenhouse temperature control? There are many ways to heat a greenhouse, but in this article, we’ll focus on the most common methods that you can easily do at home.

1. Get more sunlight

When building a greenhouse, choose a place without trees or buildings to block the sun. This will allow the greenhouse to get enough heat during the day even in winter when the sunshine hours are short. And release it slowly at night.

2. Add thermal mass

Before considering any heating system, it is important to consider how to absorb the heat already in the system. Materials with high thermal mass include soil, clay, stone, water, brick, and ceramic. Placing more of these materials in the greenhouse enables the capture and storage of more energy, as well as the regulation of the temperature.

3. Cover the greenhouse with cotton cloth

Covering the greenhouse with thermal blankets or heavy curtains on cold nights can significantly reduce heat loss. This method is simple and especially suitable for sudden cold weather. You can buy specialized greenhouse insulation at your local garden store or online, or use the thick fabric from home as an insulation blanket for your greenhouse.

It is recommended that you choose a lightweight material with good insulation. Install hooks or brackets on the greenhouse frame to easily open it during the day.

4. Use double-layer plastic film

Plastic film is suitable for heat preservation of small and medium-sized greenhouses. An air layer is formed between the two layers of plastic. When the heat inside the greenhouse tries to dissipate to the outside, this air layer will act as a barrier. Instead of being directly dissipated to the outside through the outer film, it effectively stores heat in the greenhouse. Studies have found that the air layer between the double-layer plastic film can improve the insulation performance of the greenhouse by about 30% - 40%. In a greenhouse using a single-layer plastic film, the temperature drops by 3 - 4 degrees Celsius per hour at night; while in a greenhouse using a double-layer plastic film, the temperature drop can be reduced to 2 - 3 degrees Celsius per hour. 

5. Make compost in a greenhouse

The composting process involves microorganisms decomposing organic matter. Microorganisms' metabolic activities consume energy, which is released in the form of heat. In the early stage of composting, the internal temperature can quickly rise to about 50-70℃. The heat generated by a normal-sized compost pile can raise the temperature of a small area around it.

During the composting process, water will participate in the metabolic activities of microorganisms, and a certain amount of water will evaporate into the air. It can reduce the heat loss caused by excessive dry air. However, when making compost in a greenhouse, you must pay attention to controlling the materials and quantity. If it is not well controlled, it may produce unpleasant odors and affect the environment of the greenhouse. Secondly, composting may attract some pests or small animals, such as mice, which may cause damage to plants in the greenhouse. 

6. Hot water heating system

The boiler is the core equipment of the hot water heating system. There are oil boilers, gas boilers or electric boilers to choose from. Oil boilers and gas boilers have fast heating speeds and high power, which are suitable for large greenhouses. Electric boilers are more environmentally friendly and easy to control, which are suitable for small greenhouses. When hot water flows through the pipes, the heat is released, heating the surrounding area and materials. Taking a greenhouse with an area of 100 square meters as an example, using a 10-kilowatt electric boiler to raise the greenhouse temperature from 10 degrees Celsius to 20 degrees Celsius takes about 1-2 hours and consumes 10-20 kWh of electricity.

7. Heater

The heater is the most direct and quick way to increase the temperature of the greenhouse. For example, a gas heater can make the greenhouse temperature start to rise within a few minutes to ten minutes after it is turned on. This is very effective for dealing with sudden cooling weather or when it is necessary to quickly reach a temperature suitable for crop growth. It is also easier to install than a ground source heat pump system, and is a very suitable choice for small greenhouses or greenhouses that need to be heated temporarily.

Its disadvantage is that the operating cost is high. If use a heater to maintain the greenhouse temperature for a long time, you will bear a relatively large energy cost expense.

8. Wood

As propane becomes more expensive, wood and pellet stoves are becoming more popular. They operate more efficiently and are less expensive than other fuels. When installing a wood stove in a greenhouse, you need to comply with local regulations.

When a small, slow-burning wood stove is placed in a greenhouse, the heat generated by the combustion is transferred to the interior of the greenhouse by heat radiation and convection. Plastic and other flammable coverings are not suitable for placing wood stoves because the chimney will get very hot as the fuel burns.

9. Bubble film

For plastic greenhouses, bubble film can be attached to the inner lining. Bubble film with large bubbles is equivalent to adding a layer of insulation, slowing down the transfer of heat and preventing air convection. Some high-quality bubble films may have certain reflective properties. It can reflect part of the heat and reflect the long-wave infrared rays radiated by plants and the ground back into the greenhouse.

10. Hot air blower system

In cold weather, hot air blowers can provide a suitable growth temperature for plants in winter greenhouse. Hot air blowers have two main advantages. First, compared with other heating options, they can quickly raise the greenhouse temperature. Second, by adjusting the outlet direction and wind speed, they evenly spread the hot air throughout the greenhouse. This helps plants grow uniformly. However, the price of industrial hot air blower systems is usually higher, generally more than $1000.

What approaches do you adopt to heat the greenhouse? We welcome you to share your experiences with us.