Experimental performance investigation of glazing system combined with internal roller blinds

Modern low-energy buildings are often associated with efficient shading devices, as an inevitable component to reduce the peak heat gain in the building and to improve visual comfort. Internal shading devices may have inferior performance compared to external shading, but these are still the most used in practice due to lower cost, simplicity and better acceptance between architects and users.

The interplay between glazing systems and internal shading devices has been studied and in everyday practice this interplay is described by the solar shading coefficient and the total g-value of the system (window + roller blind). Solar shading coefficient in such practice is assumed to be independent of the window properties and solar incidence angle.

This paper is aimed to illustrate the deviation between the actual and assumed performance of the window system with internal roller blind. This task is carried out by experimental work in a full-scale test facility, the Cube, with two types of window (double and triple glazed) and two types of solar shading: highly reflective roller blind and highly absorbing roller blind. Danish Building simulation software, BSim is used to illustrate the scale of deviation between the experimental results and the results obtained with common assumptions for solar properties of shading device.

It is concluded that the solar shading coefficient for an internal roller blind, as a standalone parameter, is not good enough to describe the solar properties of the system, as it is proven to be angle-dependent. Further work is required to investigate the relation between the solar shading coefficient of shading device and window properties.