We are somewhat taken aback by the design stage energy efficiency rating and environmental impact rating that we have achieved for Clayhill Farm eco dwelling in Lavenham. By using super-insulative natural materials such as hemp, sheeps wool and wood fibre we have created a highly efficient building envelope that doesn't cost the earth. Hempcrete is cast into an inner studwork leaf to provide thermal mass to the internal spaces. An outer studwork leaf is filled with sheep wool and then the whole wall is wrapped with wood fibre board to ensure no cold bridging.