Technical White Papers
The Breathe Homes Technical White Paper Series is an open technical resource exploring building physics, moisture safety, and vapour-open retrofit for historic and traditional buildings. Grounded in hygrothermal science and practical on-site delivery, each paper investigates critical challenges. From lime binder chemistry and wood fibre IWI detailing to moisture buffering and crack diagnostics, helping architects, specifiers, and homeowners create durable, healthy, low-energy homes.
Related Services
These papers describe how we work. The practical side is under services: lime plastering, natural insulation, wall remediation, lime rendering and brickwork restoration.
Overview
Over a third of the UK’s building stock was constructed before 1919, from solid masonry bedded in lime mortar, with no cavity and no membrane between the wall and the weather. These buildings were never watertight in the modern sense. They were built to absorb moisture and release it again, cyclically, through the full thickness of the wall.
In the urgent race toward decarbonisation, modern retrofit practice tends to reach for the opposite: seal the fabric, add an impermeable layer, and stop the exchange. On a building with a cavity and a damp-proof course that is sound engineering. On a solid wall it interrupts the only drying mechanism the wall has, and the damage takes years to surface.
The pursuit of arbitrary, spreadsheet-derived U-values has produced a great many warmer buildings with wetter walls and rotting joist ends. These papers exist because we would rather do the harder, slower thing properly.
Our Philosophy
One principle underneath everything else: a wall built without a cavity or a damp-proof course has to be able to dry, and every material we put on it has to let that keep happening. Four things follow from it.
- Moisture over heat loss. A wall that keeps water out on a datasheet can still trap it in practice. We choose materials that let a wall keep drying rather than ones that only test well sealed shut.
- The material has to match the wall. Solid brick and lime mortar move and breathe in ways a modern cavity wall does not, so we specify non-hydraulic and natural hydraulic limes, wood fibre and clay to suit, not whichever material is easiest to source.
- Comfort is more than a heat-loss number. How warm a surface feels and how well it buffers humidity through the day matter as much to a room as its measured U-value, and often more.
- There is no single right answer. Fat lime or NHL, clay or lime, internal or external insulation: the right choice depends on the specific wall in front of us, its exposure and its history, not a rule that applies everywhere.
Who This Is For
These papers and the service pages behind them are written for anyone who wants the reasoning as well as the answer.
Examples
- Architects and heritage consultants, who need the building physics to hold up against a conservation officer, not just a materials list.
- Retrofit assessors and coordinators, who want real hygrothermal evidence such as WUFI modelling behind a specification, not a generic RdSAP assumption.
- Specialist contractors and tradespeople, who want material behaviour, curing times and joint detailing explained properly rather than guessed at on site.
- Homeowners planning a whole-house retrofit, who want to know what they are buying before it goes on the wall.