Developers, architects and builders must incorporate carbon reduction measures into construction

With all the talk about agriculture and transport being the chief culprits of Ireland’s high carbon emissions, it’s hard to fathom that 37 per cent of emissions are related to building and construction.

However, if you break down that figure, it becomes a little clearer. About 23 per cent of emissions from buildings come from so-called operational carbon (ie the carbon used to run the lighting, heating and cooling systems in buildings) and 14 per cent comes from embodied carbon – which is all the carbon dioxide emitted during the construction and design of buildings.

Embodied carbon includes everything from the quarrying and mining of raw materials to the manufacturing, transportation and installation of construction products in buildings. It also includes maintaining, replacing, removing and disposing of materials as buildings are demolished or upgraded.

Ireland has ambitious legislation and policies on operational energy use in buildings but embodied carbon emissions remain unregulated

So as the energy demands of buildings are slowly being reduced with better insulation and more renewable energy heating and ventilation systems, attention is now turning to embodied carbon – which up to now has been a somewhat neglected contributor to greenhouse gases.

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The Irish Green Building Council (IGBC) commissioned the carbon modelling report (which the above operational and embodied carbon figures come from) from researchers in the Building in a Climate Emergency research laboratory at the School of Architecture, Planning and Environmental Policy at University College Dublin.

“Ireland has ambitious legislation and policies on operational energy use in buildings but embodied carbon emissions remain unregulated,” says a spokesperson from the IGBC. Embodied carbon emissions are already regulated in countries including Denmark, Finland, France and the Netherlands.

This scenario is however likely as change with proposed revisions of the Energy Performance of Buildings Directive (which previously introduced Ber energy ratings and Nearly Zero Energy Buildings (NZEB) standards in Ireland). With these revisions, the so-called life cycle global warming potential will have to be calculated for all large new buildings from 2027 and for all new buildings from 2030. This measure will include data on both operational and embodied carbon in buildings.

Ireland’s latest climate action plan announced by the Government last December also seeks to cut the embodied carbon emissions for materials produced and used in Ireland by 10 per cent by 2025 – and by 30 per cent by 2030.

Meanwhile the Royal Institute of the Architects of Ireland (RIAI) have issued a “climate challenge” to all architects which says that architects “must act now to ensure that new and retrofitted buildings deliver net zero whole life carbon as soon as possible”. The challenge includes 2030 targets to reduce operational and embodied carbon as well as water use in an “outcomes based building performance” model.

However, while all these targets look good on paper, there is currently very little information on the embodied carbon of Irish buildings. “Developing high quality data is a critical first step in building more sustainable homes. The industry is still not committed to publishing performance data on buildings,” says Simon Keogh, senior architect with COADY Architects in Dublin.

Keogh, who is also on the RIAI Sustainability Taskforce, was the senior architect on Kilbride Court, a social housing scheme in Bray, County Wicklow. This project was the first multi-unit development to be awarded a gold certification under the Home Performance Index (HPI) from the IGBC.

“The importance of this project was that it measured 35 sustainable indicators including embodied carbon to the European EN15978 standard and complied with the RIAI climate challenge 2025 on embodied carbon targets using business as usual construction (strip concrete foundation, concrete cavity block walls). And by doing so, we demonstrated that the typical build is not designed to deliver the significantly lower embodied carbon that is required by 2030,” Keogh explains.

We have to deliver half a million homes over the next 20 years which is where most of the environmental impacts of construction will come from

Kilbride Court still achieved gold certification in the HPI because of several other measures that were taken. These include using bio-based cellulose insulation (recycled newspapers) in the attic and reduced water flow on taps, showers and toilets. The actual energy consumption and indoor air quality of the buildings continues to be assessed since people moved in to see if any further improvements are needed.

The HPI takes a holistic approach to evaluating the sustainability of new housing with 35 measures on carbon emissions of energy, embodied carbon, biodiversity, land use, water use, universal design and accessibility to public transport, schools and amenities.

Keogh believes architects need to use accurate software to ensure the building performs at its best and is not, for example, overheating the interior and then needing fans to cool it back down again. He also says that architectural materials with environmental product declarations (EPDs) should be prioritised.

“Also, there is a need to move from high embodied carbon products like concrete and steel to lower embodied carbon materials like timber until the carbon impact from concrete is fully and assessed,” Keogh says. For example, dry concrete products such as precast slabs, stairs, paving, door lintels and window sills made from granulated blast furnace slag, a byproduct of steel manufacturing, emits 96 per cent less carbon than standard Portland cement.

The RIAI climate challenge also encourages architects to use materials more sparingly, to design buildings for adaptable use and to choose those that have the potential to be disassembled and reused. It also encourages architects to avoid building redundant unnecessary space or non-functional features.

According to a recent article in Passive House magazine, manufacturers need to “step up to the plate” by getting independently validated environmental product declarations (EPDs) or product environmental passports which would provide accurate information on the carbon used over the lifetime of the product (also known as life cycle assessments). In Ireland, verified EPDs can be published on the EPD Ireland programme (igbc.ie/epd-home) which was developed by the IGBC.

The Kilbride Court development also had pre and post construction ecological assessments which Keogh says is the first published third party verified biodiversity assessment in Ireland. And while no measures were taken to enhance the biodiversity once the building was completed due to budget constraints, he contends the data alone is useful for others to focus their minds on how construction impacts on biodiversity.

IGBC chief executive Pat Barry says targeting embodied carbon reductions in the building industry is hugely important now as the need for more housing is such a priority. “In Ireland, we have to deliver half a million homes over the next 20 years which is where most of the environmental impacts of construction will come from. We would also contend that a significant number of these new homes must be sourced from existing vacant buildings.”

The IGBC have developed the Carbon Designer for Ireland tool so that building designers can estimate the carbon impact of their projects at the early stage of building design. The IGBC see this as key because it is at the earlier stages that many of the big, most impactful decisions are made.

“Ultimately, we need to move to low-carbon forms of construction and walkable or cyclable communities. That’s the only way we are going to actually achieve a world where we stay under 1.5 degrees of warming,” Barry adds.