Breathable wall insulation · Solid wall · Period property
Breathable wall insulation for solid-wall, period and listed homes.
The right insulation for solid walls isn't the warmest — it's the one that doesn't trap moisture. Sprayed cork is Class 1 vapour-permeable, adds up to 30% thermal uplift, and works where PIR foam and cement render fail.
Why breathability matters
Old walls are designed to breathe — modern insulation often suffocates them.
Solid-wall homes built before about 1920 use lime mortar and soft brick or stone that absorb moisture in winter and release it in summer. They were never meant to be sealed. When non-breathable insulation (PIR foam, EPS board, cement render, vinyl paint) is bolted onto a solid wall, it traps that moisture inside the masonry — causing blown render, salt staining, decayed joist ends and persistent damp.
Breathable wall insulation solves the thermal problem without creating a moisture problem. Sprayed cork sheds wind-driven rain from the outside but stays open to vapour from the inside, so the wall still dries out the way it was designed to.
Insulation for solid walls
The right system for brick, stone, lime and earlier construction.
Conventional insulation for solid walls means either internal wall insulation (IWI) boards that eat 80–100 mm off every room, or external wall insulation (EWI) that buries period details under 150 mm of foam. Sprayed cork is a third option: 3–6 mm thick, applied externally or internally, no rebuilt reveals, no lost floor space, no conservation objections.
And because cork is naturally elastic, it moves with the building. Solid-wall homes flex seasonally — cork bridges hairline cracks where rigid render fails.
Period & listed properties
Insulation for period properties that conservation officers approve.
We're regularly specified on Victorian, Edwardian, Georgian and earlier homes — including Grade II listed properties — precisely because the coating is breathable, only millimetres thick, and reversible. See our heritage page for case studies.
Where damp or mould is already established, pair this system with our damp solutions and mould prevention guidance — warming the wall surface above dew point is the root-cause fix.
Why breathable cork wins on old walls
Breathable insulation for old houses — at a glance.
Class 1 vapour-permeable
Highest breathability classification. Lets moisture escape so masonry stays dry.
Waterproof to driving rain
Sheds wind-driven rain from outside while staying open to vapour from inside.
Solid-wall ready
Suitable for pre-1920s brick, stone, lime and rubble construction where foam systems fail.
Conservation-friendly
3–6 mm thick, follows original detail, reversible. Frequently accepted on listed properties.
30% thermal uplift
Genuine insulation, not just a decorative coating — measurably lower U-values on solid walls.
Natural & non-toxic
100% natural cork bark. No off-gassing, no synthetic insulation in the fabric of a heritage home.
Breathable insulation FAQ
Insulation for old houses, solid walls and period properties.
- What is breathable wall insulation?
- Breathable wall insulation is a vapour-permeable system that allows moisture inside the building to pass through the wall and escape, instead of trapping it. Sprayed cork is Class 1 vapour-permeable — the highest classification — making it suitable for solid-wall, period and listed properties where non-breathable foam systems cause damp.
- Why do old houses need breathable insulation?
- Pre-1920s homes are built from solid brick, stone or lime construction designed to absorb and release moisture seasonally. Sealing them with closed-cell foam, PIR boards or cement render traps that moisture inside the wall, causing interstitial condensation, blown render and decayed timbers. Breathable insulation for old houses keeps the wall functioning the way it was designed to.
- Is cork suitable for insulation for solid walls?
- Yes — cork is one of the very few insulation materials specifically suited to solid walls. It adds measurable thermal performance (up to 30% U-value uplift), bonds to brick, stone or existing render, and never compromises the wall's ability to dry out.
- Can you use this on insulation for period properties?
- Yes. We routinely specify sprayed cork on Victorian, Edwardian, Georgian and earlier solid-wall properties, including listed buildings. Because the coating is only 3–6 mm thick and breathable, it's frequently accepted by conservation officers who would refuse traditional EWI.
- Will breathable insulation stop damp on old walls?
- In most cases yes — and crucially without trapping it. By warming the internal wall surface above dew point you eliminate the condensation that causes black mould, while the vapour-permeable coating still lets the wall release any moisture it already holds.
- How does breathable cork compare to lime render or wood-fibre boards?
- All three are breathable and heritage-appropriate. Cork adds the best thermal performance per millimetre (3–6 mm vs 40–80 mm for wood fibre), is applied externally or internally without rebuilding reveals, and carries a 25-year warranty against cracking or detachment.