Greenhouses are widely used, even in the cold winter, the inside remains quite warm. Many may wonder why the temperature inside is so high. What is the principle of heat preservation in greenhouses? Let's take a look.

For solar radiation, plastic greenhouses and glass are almost "transparent," allowing most of it to pass through. However, for long-wave ground radiation, they are not "transparent," with very little of it able to penetrate. Thus, greenhouses and plastic sheds enable the continuous entry of external solar energy into the interior, while minimizing the loss of heat inside, thereby regulating the temperature.

Therefore, sunlight passes through the film and into the greenhouse, where it is securely trapped, resulting in higher temperatures. The ground surface also has temperature, but due to the film's barrier, cold outside air cannot enter, preventing contact with the indoor air and keeping the temperature from dropping. The film's function is to allow only sunlight in, not air, thus the indoor temperature is significantly higher than the outdoor temperature.