Many historians look at how our past can influence our future, but a group of research engineers at Ghent University in Belgium are evaluating how our future climate will affect our past.
Increasing global temperatures are affecting human lifestyles in more ways than one. Climate change may also impact the way historic buildings are degrading over time. The team at Ghent University released a study in the Canadian Journal of Civil Engineering showing that the rising temperatures in certain areas are reducing the number of freeze–thaw cycles, meaning less degradation of the solid masonry walls that hold up historic buildings.
Ancient structures were often constructed with solid masonry walls that are structurally strong but also act as moisture buffers from the outside elements. Water from wind-driven rain penetrates small pores in the brick walls that absorb the moisture until it can be released back to the outside. However, these solid walls can start to degrade once the water inside them is exposed to freezing and thawing, and as our climate is changing, so are these freeze–thaw cycles.
Freeze–thaw cycles are a common problem for buildings, roads, pipes, and other infrastructure in cities that experience winters. Water leaks into pores and crevasses, then freezes, expands, and puts pressure on anything in its way. The result is cracks and breakages in the building materials.
The paper also outlined the impact of the urban heat island effect, where a metropolitan area is warmer than its surroundings, on the number of freeze–thaw cycles by monitoring locations inside and outside the city of Ghent in Belgium. The results in Ghent showed that the urban central area of the city experienced a lower risk of freeze–thaw cycles, followed by suburban areas, port areas, and rural areas.
Because of greater human activity in urban areas, temperatures are often recorded higher inside city centres. The maximum temperature differences recorded in the study ranged between 1.46oC and 3.14oC. In the warmer urban areas, the risk of the temperatures dropping below freezing is diminished, which reduces the risk of freeze–thaw cycles impacting the structural integrity of historic buildings.
But it’s not just city centres that are affected by rising temperatures due to human impact, climates are changing all over the globe. The study identified trends across Europe regarding the effects of climate change on the number of freeze–thaw cycles. The team found that most areas (47%) are seeing a decline in the number of freeze–thaw cycles. However, some areas (14%) are seeing increased freeze–thaw activity. They identified these areas as mostly “having a northern latitude or high altitude.”
Another factor that impacts the degradation of buildings is the amount of wind-driven rain. More rain results in more saturated building walls, which means that when the temperatures drop below zero, there’s more water inside the masonry walls that is susceptible to freezing.
As historic buildings are being retrofitted to sustain the tests of time and weather, an evaluation of changing climates should be considered, as the number of freeze–thaw cycles in an area may be on the decline.
Read the paper: Does historic construction suffer or benefit from the urban heat island effect in Ghent and global warming across Europe? in the Canadian Journal of Civil Engineering.
