Demolishing substandard flat complexes for regeneration is going to the be “harder and harder to justify” under new EU energy directives due to be introduced later this year, according to Dublin City Council’s most senior architect.
New rules on “whole life carbon” in updated EU Energy Performance of Buildings directives will make it difficult to demolish and rebuild existing homes and still meet carbon emissions targets, city architect Ali Grehan has told councillors.
The council had previously favoured demolition of its older rundown flat complexes, particularly those four-to five-storey blocks built between the 1950s and the 1980s, to allow the construction of taller, higher-density apartments on the same land.
However, Ms Grehan said the emissions associated with demolition, the creation of construction waste, and the loss of “embodied carbon” – the energy used to create buildings – may rule out replacement of older flats in many cases.
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Mandatory “whole life carbon assessments” would have to be conducted at building design stage of any project, she said.
“That means that when we’re designing or renovating a building we have to look at all of the carbon emissions associated with the construction. In Ireland 37 per cent of national emissions come from the built environment, and of that 37 per cent, 23 per cent is from building operations and 14 per cent is from embodied carbon.
“That would include all of the energy that goes into extracting the materials that go into construction, transportation, and the materials themselves. Whole life carbon also looks at the energy costs of demolishing buildings and what happens with the materials when they’re become waste.”
The council had to achieve “near zero energy construction” by 2050 she said. “If we’re going to have to assess whole life carbon costs of buildings it is going to be harder and harder to justify demolition.”
A new replacement building could be designed to meet the highest energy standards, but she said: “It will perform really well but the question is what is the payback for those emissions that we will spend building new buildings and will it help us achieve our zero carbon targets by 2050?”
While the council was building new homes on vacant sites which met the highest energy ratings, it had also achieved high building energy ratings (BERs) retrofitting older housing, including protected structures, Ms Grehan said.
“In 2021 we did a pilot retrofit of two flats in Ballybough House just to see how you retrofit a protected structure. “The flats off the North Strand were built in 1939 and designed by Herbert Simms. Due to their protected status all energy interventions, such as insulation had to be internal and “very sensitively considered” she said.
“However it is possible to retrofit a protected structure like a brick flat complex and we did it to B2 Ber, which is N ZEB [near zero] for retrofit.”
The council has recently received planning permission to undertake its first “deep retrofit” of a five-storey flat complex, the 1960s complex on Constitution Hill, which was built with two storeys of duplex flats over ground floor bedsits and is a very common flat typology in the city. The project will involve amalgamating some flats to create bigger homes, as well as building new blocks on the site.
The council also plans to retrofit similar flats on the west side of Dominick Street Lower, having earlier demolished and rebuilt the flats on the east side of the road. “It’s doubtful we’d actually get more density if we demolished and rebuilt them that makes retrofit a very viable option.”
It was considering trialing different types of retrofitting solutions in each of the three flat blocks on this site as an “upskilling opportunity” she said.
“The core objective of the project is to develop an exemplar climate resilient housing solution to renovating DCC flat blocks which addresses current questions about retrofit and informs other renovation programmes.”
