Multi-layer facades: What happens behind?

Many recent buildings are equipped with multi-layer facades composed of opaque exterior elements located in front of the glazed surfaces, such as fixed external lamellas, metallic fabrics, perforated plates, wooden claddings, etc. In most cases these systems are mainly motivated by aesthetic considerations. The presence of outer layers in front of opaque parts of the facade may have a low influence on the building performance, but when windows are covered, a substantial weakening of the daylight availability and energy performance can be observed. This paper assesses three representative multi-layer facade systems and compares their performance with the one of an efficient single layer facade equipped with external automated blinds. Dynamic simulations are run with DIAL+ software (v2.5) in order to compare the energy performance and indoor comfort conditions. Simulations with the Three-Phase method are carried out to evaluate the annual daylight availability (sDA, UDI).