Information sheet for construction clients and …

1 Information sheet for construction clients and designers Cutting embodied carbon in construction projects This guidance will help you identify basic cost-effective actions to reduce the carbon impact of the materials used in your construction projects. What is good practice? As Building Regulations reduce operational emissions towards zero, the embodied CO2 emissions associated with supplying materials can be as much as 50% of total emissions over a building s lifetime. If you reduce embodied carbon, you can benefit financially from: reductions in materials use and waste; less reliance on energy-intensive manufacturing routes; and a reputation for good environmental management.

2 From the client s perspective, a simple approach to cutting embodied carbon is to set the following requirement in the project specification and design team appointment: identify the [5-10] most significant cost-effective opportunities to reduce the embodied carbon emissions associated with the project ( through leaner design, designing out waste, reusing materials, and selecting materials with lower embodied carbon over the project life-cycle), quantify the savings made through individual design changes, and report actions and outcomes as part of a Carbon Efficiency Plan In response, the design team would focus on quantifying the savings associated with just a few changes for specific project elements/components.

3 They can use existing assessment methods (and, in the future, methods compliant with the emerging European standard CEN TC350). They do not need to calculate a carbon footprint for the whole project they would simply estimate with-without differences. The following Table lists the types of action a design team should consider and the scale of savings achievable (which will vary from project to project). The examples mainly refer to buildings, although the principles apply to infrastructure projects as well. Carbon saving action Range of carbon savings Using less materials 1. More efficient building design ( compact building form) Varies by building type typically, up to 5% (of a building s total embodied carbon) 2.

4 Change the specification for building elements ( lower-weight roof design) Varies by element type and specification typically, up to 20% for major structure and cladding elements is achievable see also 6 below 3. Design for less waste on site ( to cut wastage rates on the top 10 materials from baseline to good practice) Varies depending on materials specified and extent of off-site construction typically up to 10% is achievable 4. Design for off-site construction ( to benefit from lower wastage and efficient fabrication) Varies depending on the extent of off-site construction up to 10% typically achievable 5. Design for reuse and deconstruction ( increase reuse of materials from demolition and earthworks on the current site; design a building for deconstruction at the end of its life; design a building for easy reconfiguration during its life) Significant savings on whole-life basis.

5 Little impact on embodied carbon savings on cradle to gate basis (see footnote 2) Using alternative materials 6. Select materials with lower carbon intensities ( cement substitutes such as PFA or sustainably-sourced timber) Varies by building type and specification typically, up to 20% is achievable 7. Select reused or higher recycled content products and materials ( reclaimed bricks, higher recycled content blocks, locally recycled aggregates) offering lower carbon intensities Varies by extent of reusable materials available typically up to 10% is achievable for some elements 8. Select materials with lower transport-related carbon emissions ( locally-sourced aggregates) Varies by transport volumes and modes typically up to is achievable, and more in infrastructure projects 9.

6 Select materials with high levels of durability and low through-life maintenance ( facades and fixing components which last as long as the building frame) Significant savings on whole-life basis. Little impact on embodied carbon savings on cradle to gate basis (see footnote 2) 2 What is embodied carbon? The carbon dioxide emissions associated with making a building as distinct from using it are referred to as embodied carbon. More precisely, embodied carbon covers greenhouse gas (GHG) emissions1 that arise from the energy and industrial processes used in the processing, manufacture and delivery of the materials, products and components required to construct a building.

7 The emissions associated with maintaining, repairing, replacing and disposing of these materials and components over the lifetime of the building can also be calculated, although CEN TC350 is expected to treat these emissions separately2. Why is it important? Embodied carbon can be as much as the carbon emissions that come from operating a building ( from the energy used for heating, lighting, air conditioning, etc often referred to as operational carbon ) over its effective lifetime3. If the UK is to achieve its ambitious target of 80% reduction in carbon emissions by 2050, closer attention will need to be paid to embodied carbon in construction by project teams as well as policy-makers.

8 Operational carbon emissions are being reduced via successive changes to the Building Regulations, and this often involves greater use of material resources ( extra insulation, thermal mass, etc). As a result, the significance of embodied carbon is increasing. Unpublished comparisons of office projects indicate that embodied carbon per m2 of floor area varies by a factor of 2-10, with significant (10%+) savings available from individual design choices. How to reduce it Generally, buildings that are efficient in terms of the amount of materials used to construct them tend also to be efficient in terms of embodied carbon and construction cost.

9 Additionally, it is often possible to find a cost-effective alternative material that fulfils the required need but has lower embodied carbon. As outlined above, a simple requirement in the client s procurement documents can catalyse the search for options as part of the design development and value engineering process. What s important is to focus effort on identifying and quantifying just a few significant savings (as illustrated below). The design team would be expected to identify changes which are at least cost neutral (or cost saving when identified in the context of a value engineering process), and ensure approval by the structural engineer where appropriate.

10 Using less materials Your design team can use less materials in construction by looking at: the overall efficiency of the building design (in terms of, for example, rationalising the building form; avoiding over-engineering the building structure, etc); ways of reducing waste focusing attention on a few materials and opportunities for off-site construction4; and planning to maximise the reuse of materials already available on site ( by reclaiming demolition and excavation materials), and designing for ease of reconfiguration and deconstruction of the new build. Overall building efficiency Generally, efficient building forms use less materials because: the ratio of external walls to floors (wall/floor ratio) is minimised; the need for bracing to the structural frame (to manage wind loading) is reduced; compact forms can enable natural ventilation by having spaces no further from the building perimeter than, say, 6-7 metres whereas deep forms may require mechanical ventilation and/or air conditioning systems; and the need for vertical circulation (lifts/stairs) may be reduced with a more efficient building layout.