Konrad Fisher was an herectic against outside thermal insulation on walls with a rendering. According to him, all thermal insulation except (closed cells) cellular glass develops mold and other problems in the rendering, which make look the rendering dirty. The rendering has to be cleaned regularly or to be treated by harmfull and expensive fungicides. Bot operations have a large cost.
In his opinion, cellular glass, due to his closed cell structure is a much better alternative, which does not become wet and will not induce mold on the rendering. He explains everything in a YouTube movie, however in German.
He also mentions the price of cellular glass but he is clearly not aware of the new generation cellular glass from GLAPOR at 250€/m³. In this case, maintenance of the will be much lower, generating a payback for the cellular glass.
Above, you observe a dirty rendering due to mold and on the right the solution according to Konrad Fisher with cellular glass in his hands. These pictures can be found in the YouTube movie.
BELGLAS BV 
Sir, How many kinds of glass foam production process is available? and How much money does a Glapor 5 cm gfi board ex work in Germany?
Many recipes are available. As foaming agent we have carbon black, water glass / glycerin , SiC, …
What about, why you dont use bigger moulds (for ex. 6 m3 of moulds 6 mt lenght, 0,6 mt height and 1,2 mt width) instead of small boxes? This makse it possible to produce much faster and much higher quantities!
Mould are old fashion. Today, we work with an endless foaming system in the same way flat glass is produced.
is it suitable for gravel ? i think it is not suiatble for blocks?
The continuous foaming on a belt is suitable for gravel and blocks (boards).
Sir, The silicate foam by alcaline silicates…can it be a storng and cheaper alternative instead of foam glass? Acc.to literature behaviour is same but structure is different!