Carbon Emissions & Net Zero in the Built Environment
The built environment has a critical role to play in addressing climate change by reducing both operational and embodied carbon emissions.
Our planet is experiencing a climate crisis. Over the last fifty years, rapidly increasing emissions of greenhouse gases such as carbon dioxide, from burning fossil fuels, deforestation, and agriculture, have fuelled rising temperatures, leading to weather extremes, natural disasters, economic disruption and increased conflict. Because of these emissions, the Earth’s temperature is now almost 1.5 C warmer than the pre-industrial average and in Ireland, 2022, through 2025 are the four hottest years on record.
Construction and the built environment are responsible for 37% of Ireland’s greenhouse gas emissions, the joint highest-emission sector along with agriculture[1]. Two-thirds of our built environment emissions are operational emissions from heating, lighting, cooling and powering our buildings. One third are embodied emissions associated with the construction, maintenance, and demolition of buildings, particularly the extraction, processing and transporting of building materials.
But the built environment can also be part of the solution. Designing low-carbon homes, offices, shops and infrastructure goes hand in hand with creating high-quality, liveable neighbourhoods in vibrant towns and cities.
To achieve this, we must consider carbon emissions at every stage of a building or structure’s life cycle. The IGBC’s Building A Zero Carbon Ireland roadmap contains three core strategies for reducing the life-cycle emissions of buildings and infrastructure:
Prioritise what we build based on social & environmental need
- Prioritise what is built under the National Development Plan (NDP) to meet citizens’ necessary housing, health, sustainable transport, economic and educational needs.
- Avoid new construction by prioritising alternatives to building new
- Reduce the size of the proposed building
- Prioritise compact and efficient structures in smart locations. Apartments, duplexes and terraces typically produce less carbon emissions than detached houses because they use materials and infrastructure more efficiently. Building homes within existing settlements produces fewer emissions than building on greenfield sites.
Optimise use of our existing building stock
- Prioritise re-use over new build. Retrofitting a residential building produces one-quarter of the carbon emissions of building a new one3.
- Reusing buildings also avoids the carbon emissions associated with constructing new infrastructure.
- Reuse materials from deconstructed buildings, and design for deconstruction and disassembly. This will mitigate future emissions associated with demolition and reconstruction.
Reduce the carbon intensity of new construction by at least 50%
- Set a target for the building’s life-cycle emissions
- Design and construct buildings to be highly energy efficient (i.e., to need minimal energy for heating, lighting and cooling during their operational phase)
- Design for durability and adaptability.
- Use fewer and simpler mechanical, electrical and plumbing systems
- Select natural, bio-based materials, products and systems (e.g., if grown and harvested sustainably, timber typically has a much lower carbon footprint than steel or concrete). Select recycled materials, products and systems.
Building a Zero-Carbon Ireland
In 2022, the Irish Green Building Council published Building A Zero Carbon Ireland, our roadmap to decarbonise Ireland’s built environment across its whole life cycle – both operational and embodied emissions. While operational emissions are on a downward trend in Ireland, we risk blowing our climate targets for 2030 if we do not tackle embodied emissions, due to the volume of construction that is planned.
Calculating life-cycle emissions
A growing number of building designers, developers and consultants are now trying to understand the full carbon footprint of their buildings by undertaking a life cycle assessment. Under the new Energy Performance of Buildings Directive, the life-cycle emissions of buildings will have to be measured and reported in the BER from 2028 for buildings over 1000m2, and from 2030 for all buildings. The first limit values for life-cycle emissions, also known as life-cycle global warming potential (GWP), will also be introduced from 2030.
The Sustainable Energy Authority of Ireland has developed a methodology for calculating the life-cycle GWP of buildings in Ireland, along with a workbook and a building materials database. It will become the national methodology for quantifying emissions and reporting them in the BER.
To learn more about life-cycle GWP, you can:
- Take IGBC’s Embodied Carbon 101 course.
- Join our quarterly “Carbon in the Built Environment” Community of Practice – search for the next meeting here
- Subscribe to our quarterly “Carbon in the Built Environment” monthly newsletter (members-only). Contact [email protected] to update your interests and start receiving updates.
IGBC’s work in this field
Since 2022, we have launched our “Building a Zero Carbon Ireland” Roadmap and Industry and Policy reports that can be found here. We have developed a methodology and data for calculating the life cycle GWP of buildings, and ran several projects to progress decarbonisation in Ireland. We have a quarterly community of practice and newsletter for our members.
Projects
[1] Whole Life Carbon In Construction and in the Built Environment in Ireland (V4) – Irish Green Building Council
Guide
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