The School of Natural Building are delighted to announce the publication of an Environmental Product Declaration (EPD) for Straw as Insulation Material in the UK. For the first time this gives an accurate assessment of the environmental impact of straw production in the UK. This was made possible by the European Up Straw Interreg-funded project.
The EPD, which can be found here, is registered on the Environdec International EPD System and is a cradle to grave EPD.
Please note that some EPDs especially the older ones are NOT cradle to grave, but only cover the first 3 stages of the Life cycle – this can make them misleading when making comparisons as they do not include the environmental impacts of their end of life carbon emissions.
EPDs are formal declarations of the environmental impacts resulting from production, use, and disposal of a product. They follow strict standards of calculation methods and reporting, detailed in European standard EN15804. Before publication they are externally verified to ensure all calculations are correct and that the results are compliant with the standard. The latest version of the standard (EN15804+A2) requires more detailed reporting of carbon emissions than older versions, with biogenic carbon (in this case carbon absorbed by the straw as it grew), fossil fuel carbon emissions, and emissions resulting from land use change all reported separately.
The EPD reports a full range of environmental impact indicators but of most pressing importance are the carbon emissions:
- Across the whole lifecycle (from production of strawbale to eventual disposal of straw once a building is demolished), the carbon emissions of 1 cubic metre of UK straw (at density of 100 kg/m3) are 14.12 kgCO2e/m3.
- A cubic metre of straw stores 129.25 kgCO2e (biogenic carbon).
- The whole life carbon impact from land use and land use change is 0.02 kgCO2e/m3
The data from the UK Straw EPD can be used to assess the whole life carbon impact of buildings using straw, in combination with EPD data for the other materials involved.
The EPD is specific to the environmental impacts and material/energy inputs to straw production in the UK.
The first chart below compares the whole life carbon emissions of straw to a selection of common insulation materials, given as the emissions resulting from 1 m2 of material at sufficient thickness to achieve a U value of 0.14 W/m2K . Straw has by far the lowest emissions.
The second chart compares the amount of carbon stored by the same. Here straw is only outperformed by woodfibre sarking.
The final chart compares the whole life carbon emissions (based on a reference example building life cycle of 60 years) emissions resulting from 1 m2 of four walls of similar structure: insulation placed between timber I-Beams, with wood fibre board and lime render externally, and plasterboard with gypsum plaster internally (this is used to provide a fair comparison between the insulation materials, not as a recommendation of building technique). The U value of all four walls is 0.15 W/m2K. ‘A’ on the chart refers to life cycle stage A – emissions up to completion of a building; ‘B-C’ refers to lifecycle stages B-C – use and ultimate disposal of a building.