Do Greenhouses Stay Warm In The Winter?

Greenhouses are often associated with warm weather and thriving plants, but have you ever wondered if they stay warm during the colder winter months? In this article, we will explore whether greenhouses are able to maintain a comfortable and suitable environment for plants when the temperatures drop. So, if you’re curious about the fate of greenhouses in the winter, keep reading to find out the answer!
Yes, with the right heating methods, insulation, and heat retention techniques, greenhouses can indeed stay warm during the winter months. By creating a suitable environment for your plants, you can extend your growing season and provide a cozy, protected space for them to thrive. In this article, we will explore various strategies and techniques for keeping your greenhouse warm in the winter.

Heating Methods

Passive Heating

Passive heating is a natural and energy-efficient way to warm your greenhouse during the winter. This method relies on several factors, such as the angle of the sun, the greenhouse’s orientation, and the use of thermal mass materials. Thermal mass, such as water-filled containers or concrete floors, absorb and store heat during the day and release it when temperatures drop at night. This helps maintain a more stable and warmer environment inside your greenhouse.

Active Heating

In cases where passive heating is not sufficient, active heating systems can be employed to regulate the temperature inside the greenhouse. Some common active heating methods include electric heaters, propane heaters, hot air furnaces, or hydronic systems. These systems provide controlled and consistent heat, ensuring that your plants have the ideal conditions to thrive, even on the coldest winter days.


Double-layered Plastic

Double-layered plastic is a cost-effective and efficient way to insulate your greenhouse. By installing two layers of plastic film with an air layer in between, you create an insulation barrier that helps reduce heat loss. This method is especially useful in areas with harsh winter climates as it provides an extra layer of protection against cold temperatures and wind.

Bubble Wrap Insulation

Another popular form of greenhouse insulation is bubble wrap insulation. This lightweight and affordable material can be easily applied to the interior of the greenhouse structure. The trapped air bubbles within the wrap act as a thermal barrier, reducing heat transfer and preventing cold air infiltration. Bubble wrap insulation is a versatile option that can be used on both glazed and non-glazed structures.

Thermal Curtains

Thermal curtains are an effective way to insulate your greenhouse and retain heat during the winter months. These specialized curtains are made from thermal fabrics that have excellent insulation properties. When the temperature drops, you can close the curtains to create a warmer space, and when the sun comes out, you can open them to allow natural light in. Thermal curtains are easy to install and can make a significant difference in maintaining a comfortable environment for your plants.

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Do Greenhouses Stay Warm In The Winter?


Natural Ventilation

Proper ventilation is essential in a greenhouse, even during the winter months. Natural ventilation is an energy-efficient way to regulate the temperature and humidity levels inside the greenhouse. By strategically placing vents and windows, you can allow fresh air to circulate, preventing excessive condensation and minimizing the risk of fungal diseases. Automatic vent openers are also available, which can detect temperature changes and open or close vents accordingly, even when you’re not present.

Forced Ventilation

In situations where natural ventilation is not sufficient, forced ventilation systems can be used to maintain optimal conditions inside the greenhouse. These systems typically consist of fans or blowers that circulate air and regulate the temperature. By moving the air around, forced ventilation helps prevent stagnant air pockets and allows for better heat distribution. It is important to ensure proper sealing of the greenhouse structure and use an efficient fan or blower to prevent energy loss.

Heat Retention

Thermal Mass

Thermal mass refers to materials that have the ability to absorb, store, and release heat. Incorporating thermal mass elements, such as water barrels or concrete floors, into your greenhouse design helps regulate temperature fluctuations. During the day, the thermal mass absorbs excess heat, preventing overheating, and at night, it releases the stored heat, providing warmth to the plants. Proper placement and sizing of thermal mass elements are crucial to achieve the desired heat retention effect.

Heat-reflective Coatings

Applying heat-reflective coatings or films to the greenhouse glazing can help reduce heat loss and increase heat retention. These coatings reflect a significant portion of the infrared radiation back into the greenhouse, preventing it from escaping through the glazing. Heat-reflective coatings can be particularly beneficial in colder climates where heat loss is a concern. It is important to choose a high-quality and durable coating designed specifically for greenhouse applications.

Greenhouse Location

The location of your greenhouse plays a significant role in heat retention. Placing your greenhouse in a sheltered area, protected from cold winds or drafts, can help minimize heat loss. Additionally, locating the greenhouse in an area that receives ample sunlight throughout the day maximizes the potential for natural heating. Proper positioning of the greenhouse also considers the path of the sun during the winter months, allowing for optimal exposure and heat accumulation.

Do Greenhouses Stay Warm In The Winter?

Plant Selection

Cold-tolerant Plants

Choosing cold-tolerant plants for your winter greenhouse not only ensures their survival but also reduces the need for excessive heating. Numerous plant varieties, such as kale, spinach, and certain lettuces, can withstand lower temperatures without compromising their growth. By selecting plants that are naturally adapted to colder environments, you can create a thriving winter garden while minimizing the energy required to maintain a warm greenhouse.

Winter Crops

Winter crops are specifically cultivated to endure and thrive in colder temperatures. These crops are often selected for their ability to withstand frost and prefer the cooler conditions of the winter season. Examples of popular winter crops include broccoli, Brussels sprouts, and various root vegetables. By focusing on growing these seasonal crops in your greenhouse during the winter, you can optimize your plant selection to match the environmental conditions and enjoy a bountiful harvest.

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Heated Beds or Mats

Creating heated beds or using heating mats is an effective way to provide extra warmth to your plants. These systems are particularly useful for starting seeds or growing more delicate plants that require a consistently warmer soil temperature. By placing heating elements beneath the soil, you can ensure that the root systems remain warm and plants can establish strong and healthy growth, even in colder conditions.

Row Covers

Row covers are lightweight fabric covers placed over rows or beds of plants to protect them from frost and low temperatures. These covers act as a physical barrier, trapping heat radiating from the soil and creating a microclimate that is several degrees warmer. Row covers are easy to install and can be removed during the day to allow sunlight in. They are an effective means of providing additional insulation and protection for your plants during the winter months.


Mulching is a gardening practice that involves applying a layer of organic material, such as straw, leaves, or wood chips, around the base of plants. Mulch acts as insulation, protecting the soil from extreme temperature fluctuations, retaining moisture, and preventing weed growth. In a greenhouse, mulching overwintering plants helps maintain soil warmth and prevents cold air from reaching the root system. It also adds an additional layer of protection against freezing temperatures.

Greenhouse Design

Orientation and Sun Exposure

Proper orientation and sun exposure are essential elements of greenhouse design. Ideally, the long side of the greenhouse should face south to maximize sun exposure during the winter months. This allows for optimal heat accumulation and natural lighting. Careful consideration of the surrounding landscape and any potential obstructions, such as trees or buildings, is crucial to ensure unimpeded sunlight reaches the greenhouse.

Shape and Size

The shape and size of a greenhouse can significantly impact its heat retention capabilities. A compact and well-insulated greenhouse with a low roof height has a lower volume to heat, making it easier to maintain a warmer temperature. Additionally, a smaller greenhouse allows for tighter control of the environment and reduces potential heat losses through air leaks or gaps in the structure.

Height and Slope

The height and slope of the greenhouse also play a role in heat retention. A steeper roof slope can facilitate better snow shedding, preventing excessive weight on the structure and potential damage. A taller greenhouse allows for better air circulation and provides more space for heat to rise, helping to maintain a more uniform temperature throughout the greenhouse.

Materials Used

Choosing the right materials for your greenhouse is essential for effective heat retention. Insulated glazing, such as double or triple-pane windows, helps reduce heat loss through the greenhouse walls. High-quality weather stripping and sealing materials help prevent drafts and air leaks. The choice of structural materials, such as aluminum or wood, can also affect heat retention. It is important to select materials that balance insulation properties with durability and maintenance requirements.

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Regular Inspections

Regular inspections are crucial for maintaining the integrity of your greenhouse and ensuring optimal heat retention. Inspect the structure for any signs of damage, such as cracks, loose panels, or damaged weather stripping. Check the functionality of vents, fans, and heating systems. Any issues should be promptly addressed to prevent heat loss and potential damage to your plants.

Sealing Leaks

Sealing any potential air leaks or gaps in your greenhouse structure is vital for efficient heat retention. Drafts can significantly affect the temperature inside the greenhouse and put additional strain on your heating systems. Inspect windows, doors, and joints for any gaps or cracks. Weatherstripping, caulking, or using specialized greenhouse tapes can effectively seal these areas and minimize heat loss.

Proper Ventilation

Maintaining proper ventilation is essential for a healthy greenhouse environment. Check the operability of vents, louvers, or fans regularly to ensure they are functioning correctly. Clean or replace air filters as needed to prevent airflow restrictions. Proper ventilation not only helps regulate temperature but also prevents excess humidity and promotes airflow, reducing the risk of fungal diseases.

Supplemental Lighting

LED Grow Lights

Supplemental lighting can be essential during the winter months when natural sunlight is limited. LED grow lights are a popular choice due to their energy efficiency and ability to provide full-spectrum lighting that closely mimics natural sunlight. LEDs produce less heat compared to traditional light sources, reducing the risk of overheating your plants. They are also long-lasting and can be configured to provide the optimal light intensity and duration for different plant species.

High-Intensity Discharge (HID) Lights

High-Intensity Discharge (HID) lights, such as metal halide (MH) and high-pressure sodium (HPS) lights, are another option for supplemental greenhouse lighting. While less energy-efficient compared to LEDs, HID lights produce high-intensity light output, making them suitable for larger greenhouse structures. These lights can be used to provide the necessary light spectrum for different growth stages of plants, ensuring proper photosynthesis and development.

Temperature Monitoring


Monitoring the temperature inside your greenhouse is crucial for maintaining optimal growing conditions. Digital thermometers with built-in probes can provide accurate and real-time temperature readings. Place thermometers at various locations within the greenhouse, including near the plants and at different heights, to ensure you have an accurate representation of the overall temperature. Regularly monitor the readings to adjust heating systems or ventilation accordingly.

Automated Systems

Automated temperature monitoring systems can enhance the efficiency of your greenhouse operations. These systems use sensors to continuously monitor the temperature and can automatically adjust heating, ventilation, and curtain systems based on pre-set parameters. Automated systems provide precise control over the greenhouse environment, ensuring that your plants are always kept at the ideal temperature for growth and minimizing the risk of temperature fluctuations.

In conclusion, greenhouses can stay warm during the winter by employing various heating methods, insulation techniques, and heat retention strategies. Passive heating, active heating, double-layered plastic, bubble wrap insulation, thermal curtains, natural ventilation, forced ventilation, thermal mass, heat-reflective coatings, greenhouse location, and plant selection all contribute to maintaining a warm and nurturing environment for your plants. Additionally, incorporating microclimates, such as heated beds or mats, row covers, and mulching, as well as careful greenhouse design, maintenance, supplemental lighting, and temperature monitoring, further optimize winter greenhouse conditions. By carefully considering these factors and implementing suitable strategies, you can ensure that your greenhouse remains warm and your plants thrive even during the coldest winter months.