How warmer is a greenhouse than outside?

on November 10, 2023

Greenhouses, with their transparent walls and roof, have long been marvels of agricultural ingenuity. These structures provide a controlled environment for plants to thrive, enabling year-round cultivation and protecting delicate crops from harsh weather conditions. One fundamental aspect that defines greenhouses is their ability to maintain a warmer temperature compared to the outside world. In this article, we delve into the science behind this phenomenon, exploring the factors that contribute to the warmth inside greenhouses.

The Greenhouse Effect: A Natural Phenomenon

At the core of the greenhouse's warmth lies a concept known as the greenhouse effect. While this term is often associated with climate change, it is an inherent process crucial for life on Earth. The greenhouse effect is essentially the trapping of solar radiation by the Earth's atmosphere, allowing it to maintain a temperature suitable for sustaining life.

When it comes to greenhouses, this effect is intentionally intensified. The transparent materials that constitute the structure typically glass or plastic allow sunlight to enter freely. Once inside, this solar radiation undergoes a transformation. Instead of passing back through the walls, it gets absorbed by the objects inside the greenhouse, including the soil and plants. As these objects heat up, they emit infrared radiation, which, unlike solar radiation, is trapped by the greenhouse structure. This trapped heat warms the air and surfaces within the enclosure, creating a microclimate that is notably warmer than the outside environment.

Selective Transmission of Solar Radiation

The type of material used in constructing the greenhouse plays a crucial role in determining the efficiency of the greenhouse effect. Glass and certain plastics are chosen for their ability to selectively transmit solar radiation. These materials allow sunlight to pass through easily, as they are transparent to visible light. However, they are less permeable to infrared radiation, which is crucial for retaining the generated heat within the structure.

The selective transmission of solar radiation is a key factor in why greenhouses are warmer than the surrounding outdoors. It ensures that the energy from the sun can enter the enclosure but is then effectively trapped, creating a warmer environment that facilitates optimal conditions for plant growth.

Control of Ventilation and Humidity

Another aspect contributing to the warmth inside greenhouses is the controlled management of ventilation and humidity. Greenhouse operators can regulate the internal temperature by adjusting the ventilation systems. During colder periods, these systems can be minimized to retain heat, while in warmer weather, they can be opened to allow excess heat to escape.

Moreover, the controlled environment within a greenhouse enables the management of humidity levels. By maintaining optimal humidity, greenhouses create a more favorable atmosphere for plant growth. The combination of controlled ventilation and humidity contributes to the consistent warmth inside the greenhouse, even when external temperatures fluctuate.

The Role of Thermal Mass

Thermal mass refers to the ability of materials to store and release heat. In greenhouses, the soil, containers, and even the plants themselves serve as thermal mass. During the day, these elements absorb the heat from the sunlight, storing it for release during cooler periods, such as the night. This stored heat helps to maintain a stable and elevated temperature within the greenhouse, contributing to its warmth.

Enhanced Growing Seasons and Agricultural Benefits

The ability of greenhouses to create a warmer environment has transformative effects on agriculture. By extending growing seasons, farmers can cultivate crops throughout the year, irrespective of external weather conditions. This is particularly beneficial in regions with harsh winters or unpredictable weather patterns. Greenhouses thus provide a shield against the adversities of climate, offering a controlled and reliable space for crop cultivation.

Greenhouses and Climate Control

The principles governing the warmth inside greenhouses have broader implications for our understanding of climate control. While greenhouses exploit the greenhouse effect for agricultural purposes, the same principles can be applied on a larger scale to mitigate climate change. By understanding how certain materials trap and release heat, scientists can develop strategies to regulate the Earth's temperature and manage the impacts of global warming.


The warmth inside greenhouses is a result of a carefully orchestrated interplay of scientific principles. From the selective transmission of solar radiation to the control of ventilation and humidity, each element contributes to the creation of a microclimate conducive to plant growth. The warmth inside greenhouses not only revolutionizes agriculture but also offers valuable insights into climate control on a broader scale.

As we continue to explore innovative ways to harness and manipulate environmental processes, the greenhouse stands as a testament to human ingenuity. Understanding the science behind the warmth inside greenhouses not only deepens our appreciation for these structures but also opens doors to sustainable agriculture and climate management.