As the largest builder of residential homes in Ireland, Cairn Homes is also leading the way in reducing carbon emissions. In 2024, the company announced that it was adopting the passive house standard for all new flagship developments as a way of reducing the energy demand of the homes it builds. This significant change to strategy was identified as a way to build better homes for Cairn’s customers and directly address its Scope 3 Greenhouse Gas (GHG) emissions liabilities. Under its Scope 3 emissions targets, Cairns plans to reduce the whole life carbon emissions of the buildings it builds by 61% by 2030 — taking 2019 as a baseline.
That target is ambitious as it sounds. Scope 3 emissions encompass all indirect emissions produced in a company’s value chain, excluding those from purchased electricity. In the case of a developer like Cairn, that means estimating the so called “downstream” emissions through energy use in the buildings, sixty years after the point they’re sold. It also means “upstream” emissions — meaning the emissions released in the construction of the building. The vast majority of those emissions are released in the manufacture of construction materials.
In addition to using the passive house building standard to minimise operational carbon emissions — by ensuring substantial reductions in energy demand to run a building — Cairn is seeking to dramatically reduce the emissions associated with the construction process. For the past four years, Ecocem has worked with Cairn’s technical teams to help the company to make significant embodied carbon reductions — while working out how it can do more with less.
Cairn senior technical manager Thomas Lowry points out that there’s always been a tendency in construction for everybody, from engineers to concrete suppliers, to “over-specify”. Adding unnecessary concrete and steel can’t go on. This is why his technical team is getting involved earlier in projects, interrogating designs to find new ways of reducing embodied carbon.
Through its partnership with Ecocem’s technical advisors, Cairn has rolled out the use of 30% GGBS concrete to all in-situ elements: walls and basement slabs as well as superstructure slabs. A commonly misplaced criticism of using GGBS in such situations has been the time it takes for concrete to achieve the strength required for construction. When additional time is required for incorporation of GGBS it can typically be absorbed into a standard schedule with adjustments to the sequencing of works. While due consideration was taken before making changes to the home builder’s standard construction practice, this critique was revealed to be especially irrelevant for scale builders like Cairn.
The piles in many of their projects don’t require early strength gain because they’re not fully loaded for months, which means that the fine margins that create unnecessary anxiety when managing a smaller project schedule are not an issue. Striking times don’t lie in the critical path, and because GGBS concrete becomes stronger than high-carbon concrete over time, these piles can contain anything up to 70% GGBS.
“We’re working on a range of different initiatives,” Thomas explains. “For example, we’re trying to reduce our rebar density in our superstructure slabs by bringing our columns closer together… basically having the building doing less gymnastics than it might have previously. And you’ll find too that you can increase the amount of GGBS you’re using and it doesn’t have to impact your program.”
“Topography surveys are now done to establish the most appropriate places to build onsite. The aim is to avoid excessive excavation, and to reuse any excavated material within in the project. It’s working. At one recent project we were nine months in and zero lorries had left the site with excavated muck or stone.” “We have a unique opportunity to force the discussion, force the implementation of different measures and use our technical knowledge to get under the hood of our designs.”
The benefits of these initiatives aren’t hard to see. As well as contributing to meeting its well-publicised emissions targets, the measures taken to achieve its emissions reductions have also delivered cost savings to Cairn. This means that Cairn is continuing to lean into its partnership with Ecocem and explore how it can incorporate more GGBS into precast elements, introducing its precast supplier into the process, and enabling all participants to reap the rewards that will come.
For a developer like Cairn, those participants include large clients who are coming under increasing pressure to quantify and reduce their own environmental impacts, including housing associations and the Land Development Agency. For this reason, and in a rapidly evolving regulatory context that is set to make whole life carbon calculation mandatory for all new buildings by 2030, Cairn’s leadership on embodied and operational carbon calculation and reduction will stand its clients in good stead.
The consortium of Cairn, UCD, Kilsaran, and Ecocem has secured €50,000 in funding from Construct Innovate, Ireland’s national Construction Technology Centre, to validate an innovative low-carbon cement capable of significantly cutting Ireland’s CO2 emissions from the construction sector.
Tata Steel IJmuiden (TSIJ) and Ecocem Materials Ltd. (Ecocem) have signed a Memorandum of Understanding (MoU) to strengthen their collaboration on the development and potential use of two next-generation steelmaking slags in low‑carbon cement, mortar, and concrete applications across Europe.
