Development of an Air-Humidity and Pressure Control System for Multi-Cavity Building Envelopes, Membrane Cushions, and Façade Systems: Proof of Concept

Proof of Concept

Abstract

Multilayer air-supported membrane structures are operated mostly uncontrolled by maintaining a set pressure and the lowest possible supply-air humidity. This leads to high energy use from constantly maintaining the default pressure and the continuous drying of the supply air necessary to avoid the cushions collapsing and condensation inside the air chambers. 

Controlling pressure and humidity interactively across all chambers of the membrane cushion will enable ETFE foil manufacturers to apply functional coatings to foils, use thin-film PV, etc., which has been challenging due to the high sensitivity of coatings and applied materials to mechanical (stretching) as well as chemical (oxidation) impacts.

To address those challenges, the presented work studied the air conditions and flow patterns within the air chambers of multilayer ETFE systems. A mock-up of a 5-Layer (4-Chamber) ETFE membrane cushion was specially designed and constructed for testing. Hardware and software solutions were developed to introduce a pressure and dew-point-based humidity controller. The study also considered options for separate pressure control of the chambers and thereby controlling the stress on ETFE foils. Parametric studies were carried out to estimate the reduction in electrical energy consumption during operation. First observations showed the prevention of condensation inside the chambers and a reduction of foil stretching.

Key results will also be useful for other building envelope applications that share some key requirements, such as closed-cavity façades, for example. As of now, feasibility is demonstrated.