Lime

From Sustainable Building Resource

Lime is a key ingredient in sustainable building. It has a number of attributes that allow buildings to be healthier, lower in carbon dioxide emissions and also drier. For refurbishment it is essential to use lime in buildings that were built before 1920. These are historically the solid walled buildings typically made from stone and brick. The structure of these buildings is breathable and should be maintained as the addition of impervious cement systems (either for re-pointing or rendering) can cause a raft of problems including damp and structural damage, as well as the associated mould and drop in thermal performance.

Creating breathable structures can also, in theory, get over the need for air extractors. This reduces energy demand due to fewer draughts. Unfortunately building control does not recognise this and hence even in breathing structures they insist on extractors. Ask the people in the Wintles about this!

The breathability associated with lime, though is in question, due to the aggregates used. Lime Works is a keen advocate of using lime putty with stone dust aggregate as this works on an osmotic basis rather than just capillary, so it actually sucks moisture out of the walls when applied externally as a render.