The use and impact of manual and motorised blinds as aids to thermal and visual comfort in domestic buildings in the UK

There is significant evidence that the combustion of fossil fuels for energy has contributed to an increase in CO2 and other greenhouse gases in the atmosphere since the Industrial Revolution; there is also evidence of a parallel increase in global temperatures, all of which have contributed to climate change and detrimental environmental impacts. The built environment has made a notable contribution to these issues and in 2011 for example it accounted for 62% of global energy consumption. Up to 85% of this energy was operational (as opposed to embodied)1 and in the EU 50% was used to operate heating and cooling systems in buildings2. Consequently, several strategies have been developed to reduce energy consumption and associated environmental impact from the built environment including improved insulation. Although this has proved environmentally beneficial by reducing energy demand for heating, in conjunction with changing climate and weather patterns however, it has also contributed to a rise in the overheating incidents in buildings. This in turn has increased the demand for electro-mechanical cooling (e.g. air-conditioning and fans), the use of which negates some of the benefits of reducing energy for heating. There are many examples of contemporary buildings that have been designed to minimise thermal gain in summer and/or warm locations; this can be achieved through appropriate building orientation and/or technical design features such as those in Jean Nouvel’s Arab World Institute in Paris, France (which includes an intelligent shading system on the south façade to manage light and solar gain)3 and Alejandro Aravena’s Siamese Towers in Santiago, Chile (which incorporate a double skin to remove heat from the building)4. Many buildings do not include this type of feature or good insulation however as a result of which interior temperatures are high in summer and low in winter, and although appropriate design and correct orientation of new buildings could mitigate these issues, there is a considerable quantity of new and old building stock in the UK that does not address one or both factors successfully. Blinds, shutters and other shading products can be both retrofitted in existing buildings and incorporated into new building designs. In addition to creating privacy and security for building occupants, they can address some of the above problems in that, if correctly used, they attenuate daylight and help to reduce energy use and associated impact by limiting thermal gain in the summer and thermal loss in the winter. In the UK use of motorised and automated shading systems is increasingly popular in commercial buildings with shading systems. However the emphasis of this study is domestic buildings, where interior space, user behaviour and levels of energy consumption often dramatically differ from that in commercial buildings; for example, air conditioning is installed in very few domestic buildings and manual shading products are the most widely used. This could change as use of motorised blinds has been shown to encourage user interaction and thus improve thermal comfort, well-being and energy savings. While component materials and manufacturing processes for this type of blind system differ from those in manual blinds, they also consume electrical energy for operation and therefore overall environmental impact is higher than that of manual blinds. This paper briefly considers thermal and visual comfort, health and well-being of building occupants; it then compares the embodied and operational environmental impact of motorised blinds and associated energy savings to determine their overall environmental impact and concludes by discussing a major challenge to the construction industry that is also limiting the potential benefits of blind use.