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

Fixed external shading devices, such as louvers, are widely used to combat solar gains that can lead to excessive overheating. External roller blinds, although commonly used 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. When fully extended the blinds block solar radiation externally reducing heat gain in summer, in the winter they add thermal resistance and reduce heat loss through windows. Appropriate design and applications of external roller blinds have the potential to improve the sustainability of buildings. This paper reports on an on-going applied research project that investigates the effect of external roller blinds on the internal thermal environment and potential advantages to the sustainability of retrofitting office buildings in the UK. The first part of the paper describes a proof of concept study in which an in-situ external roller blind was installed in a ‘test’ room and its summertime thermal performance was compared with that of a ‘control’ room under the same external climatic conditions. Dynamic thermal analysis was carried out to establish the annual thermal performance of the blind, including impact on cooling and heating energy requirements. Associated annual carbon dioxide emissions were established and the blind was discovered to reduce the greenhouse gas emissions (CO2e) by 15% annually, majority of which is reduction in requirement for heating.The life cycle impact of the blind was investigated. Individual process contributing to the production, manufacture, decommissioning and transport of the blind were assessed in terms of their greenhouse gas emissions. Under the conditions of the concept study scenario and taking into account the recycle of the components, the external roller blind in operation is estimated to take approximately six months to save enough to compensate the embodied greenhouse gas emissions mainly due to the manufacturing process. The results have demonstrated there is significant potential of using external roller blinds to reduce the operational and life cycle greenhouse gas emissions of buildings in the United Kingdom.