Besides the cost price, there are two principal factors which determine the construction of a glasshouse or a Dutch Light structure: these factors are the light balance and the heat balance, which are themselves a function of the covering material of the construction, of the shape of the glasshouse and of its orientation.
It is known that the last two factors are interdependent.
The light balance of the glasshouse is discussed by the speaker as a function of the results of theoretical calculations.
The quantity of light received by the different types of glasshouses as a function of their orientation is estimated at different times of the year.
Application of these data is made in case of glasshouses with plastic covering, which can be conceived in a form differing from those of the traditional glasshouses, and better adapted to the properties of the covering material.
The heat balance of a glasshouse represents a positive datum which, according to the results achieved in the current experiments, can be considered as proportional to the light balance.
The dimensions of the glasshouse are not strange to this balance.
If the covering materials of the glasshouses have to be transparent for solar radiation, they also have to resist the heat losses.
The speaker discusses this last problem with regard to the nature of the materials and the shape and the orientation of the glasshouses.
In addition, he broaches the question of the lining of the glasshouses and the real profit that this can yield.
In conclusion, it can be confirmed that the study of the shape and the orientation of glasshouses cannot be dissociated from that of specific problems, viz. that of the covering materials.
It is this complex relation that is sought in the course of the above account.