Thermal performance of external roller blinds retrofit for offices in the United Kingdom

Fixed external shading devices, such as louvres, are widely used to combat solar gains that can lead to excessive overheating. External roller blinds, common in mainland Europe, are rarities in the UK. External roller blinds are retractable shading devices formed of horizontal slats that roll up into a casing above a window opening. They are a well developed technology with distinct advantages over fixed external shading devices. Appropriate design and applications of external roller blinds have the potential to improve the sustainability of buildings. This paper reports on a proof of concept trial that demonstrates the effect of external roller blinds on the internal thermal environment under UK climate. An external roller blind was installed in a test room and its impact on internal mean radiant temperature was compared to an internal venetian blind in a control room. Real time monitoring was carried out over the summer in 2011. A computer thermal model was established to model the test room and to simulate the impact of the external roller blind on the cooling load. This paper concludes that external roller blinds have the potential to reduce summertime mean temperature by 1.8ºC and lower peak temperature by 3.5ºC. Cooling load can be reduced by 20%. The research to demonstrate their potential is on-going.