Home sizes need to be cut by 28 per cent and the construction of detached houses discouraged, if the State is to have a chance of meeting its climate goals, the chief executive of the Irish Green Building Council (IGBC) has said.
Terraced houses are neck and neck with apartments when it comes the most carbon-efficient homes, while detached houses are least efficient, even when they have been built to the top energy rating standards, IGBC chief executive Pat Barry said.
“Our homes have been getting more energy efficient per square meter over the past 20-30 years but they have also been getting bigger so the impact of building bigger homes has offset the efficiencies,” Mr Barry told the IGBC annual conference in Dublin.
When the energy used to run homes is assessed, mid-floor apartments are the most carbon efficient, followed by mid-terrace housing, semidetached houses, then detached houses. Detached bungalows are worst of all because they have the highest ratio of exposed external area to the internal usable area.
However, the picture changes when the “embodied carbon” used to produce homes is taken into consideration. Terraced houses come out ahead of apartments, with detached houses, particularly larger homes, still the worst.
“Whole schemes of detached homes are inherently extremely inefficient,” he said.
Continuing to build these oversized, detached houses will prevent the State from meeting its targets of reducing carbon emissions by 51 per cent by 2030, Mr Barry told conference. The IGBC is a non-profit organisation which represents professionals involved in sustainable construction.
“We have huge inefficiency built into our planning system that allows oversized housing,” he said. “In 2018, 40 per cent of the built area for housing was detached housing. If you look at the efficiency that means that 40 per cent of labour and materials is going into essentially building waste space, because I don’t think anybody can justify homes of that size over their lifetime,” he said.
“If we build at the current densities, in order to deliver 400,000 homes by 2030 we will need 349 square kilometres, which is about a third of the whole county Dublin.”
There was a notion that technological advances would solve these issues, he said. “Technology won’t fix this, it does require a good dose of technology but an even bigger dose of common sense.”
Newly-built detached homes were an average size of 244sq m – typically three times larger than required, he said.
“If we look at our demographics, average size of household is about 2.5 persons per household. So if you take the amount of space needed – about 30 square metres per person – and multiply that by 2½ and you get 75sqm.
“In 2018, a very low year for housing completions, we only built 17,433 homes but that was actually 2.6 million square metres. If we were building 75sqm homes, which would probably be average a mix of one-, two- and three-beds you could have built in 35,000 homes and we would be well on the way to solving the housing crisis.”
Carbon emissions could also be substantially reduced by reducing the size of these homes by 28 per cent, in addition to sourcing 124,000 new homes from vacant buildings and spaces above shops, as well as decarbonising the national grid and retrofitting. “There’s no silver bullet it involves doing all of these things, each individually incredibly challenging.”