How to heat a small greenhouse

on November 16, 2023

Greenhouses offer a haven for plants, allowing you to extend your growing season and cultivate a diverse range of flora. However, maintaining an ideal temperature inside a small greenhouse can be challenging, especially during colder months. In this guide, we will explore various methods to effectively heat a small greenhouse, ensuring your plants thrive year-round.

Understanding Your Greenhouse:

Before delving into heating methods, it's crucial to understand your greenhouse's unique characteristics. Consider its size, insulation, and the materials used in its construction. Knowing these details will help you determine the most suitable heating strategy for your specific setup.

1. Insulation Matters:

Start by insulating your greenhouse effectively. Ensure that walls and ceilings are well-sealed to prevent heat from escaping. Double-check for any gaps or leaks that could compromise insulation. Bubble wrap or thermal curtains can be added to further enhance insulation and reduce heat loss.

2. Passive Solar Heating:

Make the most of natural sunlight by employing passive solar heating techniques. Position your greenhouse to receive maximum sunlight exposure during the day, and use materials with high thermal mass, like bricks or water containers, to absorb and store solar heat. This stored heat will be gradually released during the cooler evenings.

3. Optimal Ventilation:

Proper ventilation is crucial for regulating temperature and humidity. Invest in automatic vent openers that respond to temperature changes, allowing hot air to escape. Additionally, consider installing exhaust fans to facilitate better air circulation. A well-ventilated greenhouse is less prone to overheating during the day and retains warmth more effectively at night.

4. Electric Heaters:

Electric heaters are a popular choice for small greenhouses. Choose a heater with a thermostat to maintain a consistent temperature. Electric heaters are available in various sizes, making it easy to find one suitable for your greenhouse. Keep in mind that they can be more expensive to run, so efficiency is key.

5. Gas Heaters:

For larger greenhouses or those in extremely cold climates, gas heaters may be a more efficient option. Propane or natural gas heaters provide a reliable heat source, but proper ventilation is essential to prevent the buildup of fumes. Ensure that gas heaters are installed safely, following manufacturer guidelines.

6. Radiant Heating:

Radiant heating systems involve placing heating elements beneath benches or in the greenhouse floor. This method warms objects and plants directly, providing a more even distribution of heat. While installation may be more complex, radiant heating is energy-efficient and minimizes heat loss.

7. Heat Retention at Night:

The challenge often lies in retaining heat during the night. Consider using thermal mass, such as barrels filled with water, inside the greenhouse. These will absorb heat during the day and release it slowly at night, maintaining a more stable temperature.

8. Soil Heating:

Ensure your plants' roots stay warm by investing in soil heating cables or mats. These can be placed directly in the soil or beneath benches. Warmer roots promote healthier plant growth, especially for heat-sensitive crops.

9. Cold Frames and Cloches:

Extend the growing season by incorporating cold frames or cloches. These mini-greenhouses provide additional protection to individual plants or rows, capturing and retaining heat effectively.

10. Monitoring and Automation:

Invest in a quality thermometer and hygrometer to monitor temperature and humidity levels. Automated systems, such as thermostats connected to heaters and ventilation, can make the process more hands-free, adjusting settings based on real-time conditions.


Heating a small greenhouse requires a thoughtful combination of strategies tailored to your specific needs. Whether you opt for electric heaters, passive solar techniques, or a combination of methods, understanding your greenhouse's unique characteristics is essential. By creating a well-insulated, well-ventilated, and appropriately heated environment, you can enjoy a thriving garden year-round, turning your small greenhouse into a horticultural haven.