Research has questioned the housebuilders’ argument that replacing old houses with new ones cuts CO2 emissions.
Over 50 years, extensive refurbishment of an old house is as good a carbon-saving tactic as demolishing it and building a highly insulated new one. So says a report by the Environmental Homes Agency and the Building and Social Housing Foundation.1 New homes cause far less CO2 to be emitted from year to year than old ones. Building Regulations have over the years ramped up levels of insulation and draught-proofing in new build so that they now require less fossil fuel to heat them.
But building a new home also represents an initial surge in emissions. The largest contributor is the CO2 emissions embodied in the brickwork, which needs large quantities of energy for extracting and processing raw materials to firing in kilns. Making cement adds further emissions, as does the transport of finished construction materials to the building site. Refurbishment carries a far lower initial burden, and boosting energy efficiency also reduces ‘in use’ emissions. But which offers larger long-term CO2 savings?
The research aimed to answer this question by comparing three typical new homes, all built to 2002 Building Regulations or better, with three extensively refurbished old homes of similar size. ‘In use’ emissions were estimated, as were the total emissions associated with building the new homes and refurbishing the old ones.
The study found CO2 emissions associated with new houses were 4.5 times higher than those for refurbishing old ones, after adjusting for their different sizes. A typical 100-square-metre new home creates 47.5 tonnes of emissions in construction. But refurbished homes produced 33% higher in-use emissions. The typical 100m2 new home caused 2.4 tonnes a year of CO2 emissions through space and water heating and electricity consumption.
Over 50 years, lifetime in-use and from construction emissions from a new house were similar to those from a refurbished home. For both, the total from a 100m2 home would be about 170 tonnes of CO2. The researchers chose 50 years because after that both types would need extensive refurbishment.
The case for replacement becomes stronger if new homes have higher energy efficiency than those few featured in this study and use low-carbon materials in their build. The government is committed to raising standards. From 2016, all new homes will have to be zero carbon (ENDS Report 391, pp 42-43 ). But the study did not include CO2 emissions caused by energy use during construction, nor emissions caused by demolishing homes and dealing with the wastes. And if new homes are built on greenfield sites, there will be extra emissions because of their occupants’ higher car mileages.
The Empty Homes Agency said the research strengthened the case for urgent government support for bringing 150,000 long-term empty homes in England back into use.