Energetic optimization

With a double-layer glazing window about 70% of the sunlight gets into the building’s interior without any sun-shading. 

With an interior high-reflective sun-shading material the amount of heat coming from outside will be reduced considerably. Only about 3 % of the solar heat will come into the room. However, the darkening effect will be considerable.

Thus a discrepancy between daylight and energy transmission.

A very stiff and inflexible curtain will not cause much living comfort (let’s say: “it’s hanging bad”) and that’s the reason why such a curtain will seldom be drawn. However, in that case its heat protecting function cannot be fulfilled.

The less solar heat the window allows to get into the building the less the curtain –due to its reflection properties - contributes to reduce the overall energy transmission value g_tot of window and curtain.

Normally a lower energy transmission value of the curtain means more stiffness and thus the darkening effect is higher.

There is a discrepancy between a low energy transmission factor and sufficient natural light in the room that require a careful weighing. A very stiff and inflexible curtain will not cause much living comfort (let’s say it’s “hanging bad”) and that’s the reason why such a curtain will seldom be drawn. However, in that case its heat protecting function cannot be fulfilled.