Diffusive glass will scatter the direct radiation into a radiation that comes from several different directions. Compare it with a shower where the water comes in parallell in a new and clean disc, but is scattered in different directions when the shower has been used of a while. Diffusive radiation occurs during cloudy days and direct radiation occurs during clear days.
The advantage with scattering the light is that the light does not come on the same spot on the plant leaf, but instead is spread over a larger surface, which decreases the risk of too high temperatures and leaf burns, which is turn decreases the need for shading, thus increasing the plant photosynthesis and grows, since more light can be used. Also a larger proportion of the light will reach the leafs in the lower areas of the plant, so that a greater part of the plant will be used for photosynthesis during clear days.
This means that diffusive glass has it´s largest benefit during clear days in cultures with a many leafs and for crops that easily get burned. The benefit is greatest during spring and summer, when the amount of direct radiation is at the greatest level.
In the movie a glass will low iron content is showed, which increases the light transmission a few units of percentage. Whether glass with a low iron content is profitable or not, totally depends on how much light the crop needs and if there is a big production during autumn and winter, when the natural light is low.
The glass in the film comes from Horti Glass in The Netherlands and is sold by Alweco.
The glass can be even more improved with a Pilkington K Glass coating, which will reduce the need for heat power by up to 30 %.
