The decision on whether to replace or renovate housing is complex, involving factors such as aesthetics, the popularity of the housing and costs of improvements. Increasingly, note researchers Yair Schwartz, Rokia Raslan and Dejan Mumovica, the decision will also revolve around decarbonisation.
But calculations of a building’s carbon footprint tend to look only at performance once the building is occupied. In this study the researchers attempted to include the whole life cycle of the building in their comparative assessment.
The researchers selected two types of housing in London: a mid-terrace two-storey house, and for contrast a bungalow (though they acknowledge the latter isn’t a common type in London). They compared the carbon footprint of replacement (with the same building geometry) or refurbishment to minimum current standards, based on a 60-year life of the buildings. Factored in were the carbon costs of building materials used in both options.
Although the assumptions and calculations used in the study are complex, it did produce some clear results within the parameters set. Refurbishment of the terraced house was found to involve a carbon footprint 10% lower than replacement, and 20% lower lifecycle costs. While replacement performed well on space heating emissions (20% lower than refurbishment) its overall performance including embodied carbon was worse.
With the bungalow, again refurbishment was found to have a lower carbon footprint though replacement building models did perform better on heating emissions. In both cases, the greatest performance difference was in the shorter term of up to 20 years.
But what if buildings were expected to last longer? The team modelled to find the point at which replacement would overtake refurbishment in terms of performance. They found the reversal happened after only 80 years for the terraced house. But for the bungalow it was 250 years.
Refurbish or replace? The life cycle carbon footprint and life cycle cost of refurbished and new residential archetype buildings in London
