Nagel explained that they, the designers, wanted the RWE Tower to be something like a transparent "aspic", that is, a building with high transarency to make visible what occurs inside. For that purpose, an extra clear glass was required. Especially, since a triple glazing is applied to most part of the tower, this had to be selected with special care. The extra clear glass panes have 91-97% of their iron oxides eliminated, leaving little green tint, when compared to other general glass. However, other glass with 91% of the iron oxides eliminated was used for the staff restaurant in the basement and other places without triple glazing.
Also, in order to protect inside of the building from solar radiation, the glass for the basement was finished with heat-reflecting coating, and that for higher levels beyond the first floor with a Low-E coating. These arrangements are shown in the plans below. The high-performance facade with a low heat transmission rate is a very important factor of the facilities.