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Climate Change and the 'greening' of masonry: implications for built heritage and new build

 

1st greening image, reduced to 300x225 pixels at 200 pixels per inch    2nd greening image, reduced to 300x225 pixels at 200 pixels per inch

Introduction

Stone soiling and cleaning (along with associated decay) is a multi-million pound operation in the UK. Understanding how natural stone structures respond to their environment is crucial to the effective and efficient management of these buildings – and becomes even more important if that environment is changing. With recent episodes of extreme weather and improved scientific understanding of climate change, the attentionof the building industry is increasingly focused on climatic futures.


Controls on stone decay processes are rapidly changing as a result of changing climate. As such, there is a need understand decay, not just in a dynamic world, but in a world where the nature of the dynamics themselves are changing. Future climate change scenarios for the northwest of the UK typically project both increased short-term uncertainty in day-to-day weather conditions and an underlying trend towards wetter, warmer and longer winter conditions. Buildings appear to have responded to these changing climatic conditions by ‘greening’ – recent observations have shown an increase in algal ‘greening’ of external sandstone walls (a material that has shown itself to be particularly sensitive to changes in environmental regime, especially moisture related) in many places in the North West of the United Kingdom (NW UK). We hypothesize that this is caused by a combination of increased moisture and decreased air pollution, and thus reflects recent changing environmental conditions. Beyond this blatant aesthetic and physical change, it is likely that chemical weathering will be enhanced in the NW UK due to increased ‘time-of-wetness’, compared to an increase in crystallisation damage in the southeast of the UK. Prolonged and more deeply penetrating wetness should also affect other agents of decay through allowing deep-seated salt penetration and surface algal soiling.

 

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