De Beauvoir extension, material detail. A range of thermal improvements were made to the property. Chimney flues were insulated and made airtight. Wood fibre insulation was applied to the existing external walls and Aerogel perimeter insulating strips were used to reduce cold bridging.In addition to insulating, membranes and tape were specified to provide airtightness. Timber flitch beams were employed to reduce the embodied energy in the structure.