SHEEPISH Report for Energy Project Enabling Fund - Round 2

This report presents the findings from part of the Peacock and Verity SHEEPISH Development Stage project, which is funded by the North East and Yorkshire Net Zero Hub’s Energy Project Enabling Fund. The SHEEPISH project aims to develop 15 Silver Street, Masham, North
Yorkshire, using bioconstruction materials, particularly sheep’s wool insulation (SWI), become a SWI training site for installers across Yorkshire and the North East, and create a stakeholder cooperative into a robust circular SWI supply chain.

Leeds Sustainability Institute has been appointed by Peacock and Verity to consult with stakeholders to find out whether there is support for a Yorkshire-based SWI supply chain, advise on how the performance of SWI at 15 Silver Street could be monitored over time, and perform hygrothermal simulations of building elements at 15 Silver Street to assess whether there are any moisture risks associated with using SWI.

Twelve stakeholder interviews were conducted in February 2024 with participants from four stakeholder groups: Yorkshire sheep farmers; general contractors; private and social housing clients; and both SWI suppliers and wool merchants. Participants talked about their current
beliefs about SWI, barriers to its use, the potential of developing a Yorkshire SWI market and rationale behind it. Cost was perceived to be the main barrier to increasing use of SWI. Farmers were willing to supply their fleeces if it were financially advantageous to do so, but
despite the cost of raw wool making up a fraction of overall manufacturing costs, SWI suppliers and wool merchants thought there would be little opportunity to pay farmers more for their fleeces. There is already a SWI manufacturer based in Yorkshire but for a collaboration to develop, demand for Yorkshire SWI would need to grow. This could be stimulated by promoting the low-carbon, safer-to-install and breathable credentials of SWI to a potential Yorkshire client base, such as private homeowners, prestige commercial organisations, and those with historic assets or a sustainable ethos.

Literature on SWI indicates favourable performance for improving air quality, controlling moisture levels and reducing sound transmission. However, most of this data comes from laboratory testing which does not replicate the reality of a product's performance within a construction, highlighting the value of capturing in situ performance data at 15 Silver Street. A range of monitoring options, together with practical considerations, are discussed. We recommend monitoring SWI moisture levels over an extended period and measuring air
quality during SWI and conventional insulation installation periods for comparison.

Moisture behaviour and breathability of SWI is often considered to be a benefit; however, natural materials can be more vulnerable to decay due to moisture accumulation over time. Hygrothermal simulation models the movement of heat and moisture through materials in a
representation of a building element, such as a wall or roof, in response to internal and external climate conditions. Hygrothermal simulation models were used to assess the risk of moisture accumulation over time in selected external elements at 15 Silver Street following a retrofit. Modelling was carried out using the WUFI Pro version 6.7 software for four external wall build ups and three roof build ups, where each case was simulated for a virtual 3 and 10-
year period. Overall, hygrothermal simulation indicates that the proposed build ups, including those using SWI, have low moisture risk. In each of the cases modelled, total water content declined over the simulation period or reached an equilibrium state that indicates a low risk of water accumulation in the building fabric. Therefore, the use of SWI appears to be as safe as the wood fibre insulation also specified in the design at 15 Silver Street.