As one of our latest Scottish retrofit projects gains momentum and before walls start to be boarded over, we thought we would share some insight and advice on how to insulate traditional stone buildings. This retrofit project uses locally sourced and natural hemp batts to insulate an existing stone building. The batts will improve the thermal performance of the building and these are applied between robust timber framing that enables future flexibility for internal fittings and fixtures to be adapted. The hemp is a robust and breathable material (Henry Ford designed and manufactured cars with hemp fibre bodies and engines fuelled by hemp biofuel and advocated them for their practically indestructible qualities) that can be supplied in various formats and in this circumstance hemp batts are neatly friction fitted within a new timber frame inside the existing building line. Specialist Scottish installers Shelbourne & Greer have sourced these batts from a new factory in the Scottish Borders and this reduces the carbon footprint of the delivery and helps support the local South of Scotland economy. The sequence of installation for this type of internal wall insulation involves the following steps:
The removal of wall attachments and temporary disconnection of existing electrical and plumbing appliances
Setting out of the new wall lining locations - plumb and perpendicular lines are drawn to position the new wall lining locations
New timber framing installed - fixed at head, base and side - and this framework benefits from intermediate vertical and horizontal supports that enable fixings of future attachments (such as shelves, pictures, lighting fixtures and wall fixed furniture)
Friction fitting and testing of hemp panels is undertaken to tightly fill the framework with new insulation
Installation of a breather membrane (to prevent vapour penetration into the wall) on the surface of the frame
Fixing of wall covering (plasterboard or a breathable surface such as wood wool or rigid hemp batts to receive a breathable lime plaster finish) and application of window jambs
Cut outs for extended wiring (sockets and switch box locations) and extension of plumbing routes to new inset locations
Application of plaster finish
Fixing of switch and socket plates and reconnection of heating and sanitary appliances
Decoration
The good news is that generous government funding is currently available for this type of retrofit project. Watch points that we would recommend considering as part of this process include:
You will need plenty of space to store equipment and materials as well as for working (cutting timber and boards) and this may impact on other areas in your house and even outside your house
Consider (and factor in the extra costs) for redecoration of other walls in rooms that are not considered 'external walls'
Plastering is a messy trade and will require protection of existing floor finishes if you intend to keep them - consider upgrading these at the same time as the wall lining work as there will inevitably be some disruption to the existing finish (for example to cut back to new room shape)
Consider adjusting wall lights, switch and socket locations when you have the opportunity to run new circuits within or behind the new wall framing
If you are implementing other sustainable upgrades at the same time (such as window installation and air source heat pumps with underfloor heating) make sure you align those elements with the insulation works and plan for an appropriate sequence (for example plumbing adjustments and window installation before wall over boarding and wall plastering before underfloor heating overlay boards and installation)