Energy-efficient retrofitting and energy consumption in a historic city centre - an example from Lhasa

The conservation of historic buildings and urban environments can have the potential to improve the quality of life, stimulate economic development and reduce carbon emissions from energy consumption. However, given increasing expectations of indoor thermal comfort and an increasing dependency on modern living technologies, energy consumption in the urban historic environment is expected to rise. This paper examines the retrofitting of windows to historic buildings and issues of energy consumption and carbon emission in Lhasa's historic city centre, focusing on the relationship between energy use and window retrofitting. First, the thermal performance of a traditional Tibetan building in Lhasa is simulated and examined. Second, four window types for retrofitting are evaluated through computer modelling and their impacts on energy consumption are compared. Finally, the energy demand and carbon emission of the whole historic city centre with various window types are estimated and compared. In terms of energy efficiency and historic preservation, current single-layered window retrofitting practices perform badly, while windows with wooden frames and secondary glazing may achieve better performance. The approach offers the opportunity to halve the energy consumption and carbon emissions in the Lhasa historic city centre.