Haze is the cloud-like appearance caused by light scattering inside or on the surface of a transparent sample. The definition of haze is the percentage of light that deviates from the direction of incident rays due to forward scattering when the light transmittance passes through the sample. If the deviation between the transmitted light and the incident light is greater than 2.5°, it is generally qualified. At this time, the luminous flux is regarded as haze.

The definition of light transmittance is the ratio of transmitted light to incident light, and the usually reported value is the percentage of transmitted light, that is, the proportion of the flux of light passing through the glass.

It can be found by comparison. The key point of haze description is scattered light. When light shines on the greenhouse glass, part of the light will be reflected back (reflected light), part of the light will be absorbed (absorption of light), and part of the light will penetrate the material (transmitted light), but in the transmitted part of the light, some will remain The original propagation direction is called parallel transmission, and the other part of the light will be scattered internally due to the characteristics of the material. This part of the scattered light is the scattered light mentioned in the definition of haze, so the haze and light transmittance are Two different concepts.

Generally speaking, there is an inverse relationship between light transmittance and haze. Materials with high light transmittance have low haze, and vice versa. For greenhouse glass, the scattering glass is an example. When the haze value of the scattering glass is high, the scattering angle is large, but the light transmittance is not necessarily high.

When purchasing greenhouse glass, we need to consider the haze value and light transmittance separately.

The consideration standard of haze value, firstly, according to the crops grown in the greenhouse, the plants have different light-loving properties, the local climate temperature difference is different, and the haze size is different, such as: high-temperature difference areas, choose high-haze glass, which can balance the temperature difference to the greenhouse The impact.

Diffuse Glass 75 Haze

Diffuse Glass 20 Haze

From the above two figures, the contrast gap can be seen. The size of the scattered light spot of the glass with 75 haze is 375mm under the same conditions, and the size of the scattered light spot of the glass with 20 haze is 100mm under the same conditions. There is still a big difference in the light coverage area of the greenhouse.

The standard of light transmittance is still based on high light transmittance. The light transmittance of ordinary float glass is low, which has a certain impact on the light demand of greenhouse crops. The higher the light transmittance, the higher the greenhouse benefit. It can make greenhouse crops grow close to the open air condition. Because of the effects of excessively high temperature, the haze of greenhouse glass can balance these adverse effects.

At present, the highest light transmittance of glass on the market is 97.5% (the light transmittance mentioned here is the transmittance of blue-violet light, and the others are the transmittance of infrared light), and the lowest light transmittance that the greenhouse can accept is 91.5% , The light transmittance of ordinary float glass is only 88%, which is completely insufficient for the growth of greenhouse crops. It is necessary to use fill light, but it will also bring high operating costs.

The greenhouse glass that can be recommended here are: diffuse scattering glass, diffuse reflection glass, and anti-reflection glass; these three types of glass have the characteristics of haze, scattering and high light transmission.

For details, please refer to the content I posted before:

What is scattering tempered glass-the advantages and disadvantages of greenhouse glass standard greenhouse glass Scattering and haze are the key points and tempered light transmittance secondary standards

Glass commonly used in greenhouses-diffuse glass is just one of them

A "paper" to distinguish the true and false of diffuse scattering glass, the distinguishing method of diffuse scattering glass in greenhouse

Diffuse scattering glass, diffuse reflection glass and anti-reflection glass in greenhouses. Through experiments and planting comparisons in recent years, it is found that haze and scattering play an important role in the growth of greenhouse crops. Use glass with haze and scattering. Without ordinary glass, the planting efficiency is about 20% higher.