Carbon evaluation considering a hygrothermal performance comparison of stone wall retrofits

Paola Seminara, Andrew Livingstone, Julio Bros-Williamson

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract / Description of output

Improving the thermal performance of walls by adding or increasing insulation is one of the first considerations for reducing heat loss in existing buildings. In most situations, the selection of materials is determined by the cost and reduction of thermal conductance, most likely choosing high embodied carbon materials used reduce becoming a counterintuitive process increasing the building’s overall retrofit carbon intensity.
Through this research, hygrothermal performance for specific solid stone walls and the selection of insulation materials, whether they are synthetic or natural in their origin, were evaluated by comparing the embodied carbon of the products from cradle to grave boundary conditions. In addition, the research explores the potential benefits of using natural insulation products manufactured in the UK and the carbon intensity benefits it presents.
Two scenarios were evaluated involving a minor retrofit (MiR), with a U-value of 0.50 W/m²K and a major retrofit (MaR) with a U-value of 0.22 W/m²K. The distinction between the thermal improvements depended on the selected insulation type and the thickness required to meet the established U-values and hygrothermal considerations. The comparison included wood fibre insulation products using 100% softwood (100SW) fibres and one with a blend of 80% softwood and 20% hardwood (80SW-20HW) fibres, against PIR insulation boards.
The research demonstrates the advantages of using hardwood insulation (80SW-20HW), with a 16% saving in material thickness against the 100SW boards to reach the same U-values, and with the lowest level of moisture accumulated on the wall when compared to both traditional wood fibre and PIR boards.
The benefits of using the 80SW-20HW are explicated when the GWP is taken into account, with a saving of 29% and 24% against 100SW, respectively for MiR and MaR. In comparison with PIR, the 80SW-20HW boards guarantee a saving of 15% for MiR, and 52% for MaR. However, wood fibreboards are mainly imported, and greater advantages on the GWP will be achieved if the products are manufactured locally. This study shows how the GWP could be further reduced, up to 60% against PIR boards, if the 80SW-20HW is made in the UK.
Original languageEnglish
Title of host publicationMeasuring Net Zero
Subtitle of host publicationCarbon Accounting for Buildings and Communities Proceedings
PublisherEcohouse Initiative Ltd
ISBN (Electronic)978-1-9161876-5-8
Publication statusPublished - 25 Sept 2023
EventThe 8th International Initiative for Carbon Accounting (ICARB) Conference 2023 - Edinburgh, United Kingdom
Duration: 25 Sept 202326 Sept 2023


ConferenceThe 8th International Initiative for Carbon Accounting (ICARB) Conference 2023
Abbreviated titleICARB 2023
Country/TerritoryUnited Kingdom
Internet address


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