Group B · Cavity and internal walls
Breathable IWI for period homes
Wood-fibre, cork or hemp-lime systems that let solid walls stay dry.
Price by property type
Internal wall insulation (whole home)
- Mid-terrace£7,000–£14,000
- Semi / end-terrace£10,000–£20,000
- Detached£15,000–£30,000
- Bungalow£9,000–£18,000
- Flat / block£5,000–£10,000
Before grants · updated 11 October 2026 · a survey confirms the final figure.
- Best for
- Victorian, Georgian, listed, stone
- Guarantee or standard
- Moisture risk assessment (WUFI)
- Time on site
- Typically several days per room — lime plaster needs time to cure between coats.
- Typical price
- From £5,000
What it is
What is breathable IWI for period homes?
Wood-fibre, cork or hemp-lime systems that let solid walls stay dry.
Best for: Victorian, Georgian, listed, stone.
Build-up
Breathable internal insulation
- 1Lime plaster
- 2Wood-fibre, cork or hemp-lime
- 3Existing solid brick or stone — still able to dry out
Who it suits
Which homes is breathable IWI for period homes suitable for?
Is my home suitable?
Pick your property type for a straight answer on breathable IWI for period homes.
Guidance only — every home is different, and a survey confirms what suits yours.
Houses
Flats and blocks of flats
Commercial and public buildings
Usually suitable Depends — a survey confirms
Not usually suitable for 8 property types
- Detached house — Breathable IWI is designed for solid walls. Cavity walls are usually filled instead.
- Semi-detached house — Breathable IWI is designed for solid walls. Cavity walls are usually filled instead.
- Detached bungalow — Breathable IWI is designed for solid walls. Cavity walls are usually filled instead.
- Semi and terraced bungalow — Breathable IWI is designed for solid walls. Cavity walls are usually filled instead.
- Chalet and dormer bungalow — Breathable IWI is designed for solid walls. Cavity walls are usually filled instead.
- 1930s home — Breathable IWI is designed for solid walls. Cavity walls are usually filled instead.
- Post-war and ex-council house — Breathable IWI is designed for solid walls. Cavity walls are usually filled instead.
- Park and mobile home — Park and mobile homes need specialist systems, which we arrange through a partner rather than standard measures.
Materials and brands
What we use
Wood-fibre boards (Steico, Pavatex, Gutex), cork or hemp-lime with lime plaster, so the wall can dry.
Insulation brands we work with
- Knauf Insulation (Earthwool, Supafil blown)
- Rockwool
- Superglass
- Isover
- Kingspan
- Celotex
- Recticel
- Xtratherm
- Steico wood-fibre
- YBS and Actis multifoil
The exact system and brand for your home are confirmed in your written quote.
Heat, bills and EPC
What it does for your heat loss, bills and EPC
An empty cavity lets heat pass straight through the wall. Filling it lowers the wall's U-value considerably, so rooms hold their heat for longer and the heating runs less — often one of the best-value measures on an EPC for homes with unfilled cavities. Solid walls lose even more heat; lining them inside gives a similar improvement, room by room.
See the EPC points and savings for your home in the EPC plannerU-value before and after, typical heat and bill saving, and EPC points — worked out for your property.Price
How much does breathable IWI for period homes cost?
Prices change with your property type. Pick your column — the quote builder then refines it for your home.
| Measure | Mid-terrace | Semi / end-terrace | Detached | Bungalow | Flat / block |
|---|---|---|---|---|---|
| Internal wall insulation (whole home) | £7,000–£14,000 | £10,000–£20,000 | £15,000–£30,000 | £9,000–£18,000 | £5,000–£10,000 |
Indicative ranges for London and the South East, supplied and installed, including VAT, before grants. Updated 11 October 2026. A survey confirms your final price.
0% VAT on energy-saving materials
Insulation, solar panels, batteries and heat pumps installed in homes in Great Britain are zero-rated for VAT until 31 March 2027. Windows and doors are not included.What to expect
Time on site, disruption and approvals
Time on site
Typically several days per room — lime plaster needs time to cure between coats.
Disruption
High in the rooms being done, which are cleared while we work.
Planning and building control
A moisture risk assessment (WUFI) comes first. No planning permission, but listed buildings need listed building consent.
Guarantee and standard
Moisture risk assessment (WUFI). The guarantee and certification for your job are confirmed in writing in your quote.
60-second grant check
Could a grant help pay for it?
Grant eligibility checker
About 60 seconds · plain results: likely, possibly or not eligible
Before we start
What type of property is it?
Questions
Breathable IWI for period homes: your questions answered
How much does breathable IWI for period homes cost?
Typical installed prices in London and the South East, including VAT and before any grant: £7,000–£14,000 for a mid-terrace; £10,000–£20,000 for a semi-detached or end-of-terrace house; £15,000–£30,000 for a detached house; £9,000–£18,000 for a bungalow; £5,000–£10,000 for a flat. Prices updated 11 October 2026. A survey confirms your final figure.
Why do period homes need breathable insulation?
Solid brick and stone walls manage moisture by letting it dry out. Non-breathable insulation and cement plasters can trap that moisture, leading to damp and decay. Wood-fibre, cork and hemp-lime with lime plaster let the wall keep drying.
What is a WUFI moisture risk assessment?
A computer simulation of how heat and moisture move through your wall over time with the proposed insulation. It shows whether the wall will stay dry before anything is installed.
Which breathable insulation brands do you use?
Wood-fibre boards from Steico, Pavatex or Gutex, cork, or hemp-lime, finished with lime plaster. The system is confirmed at survey.
Can breathable insulation be used in a listed building?
Often, because it's reversible and suits historic fabric — but listed building consent is needed first, and we prepare the information your conservation officer will ask for.
Group B
More in cavity and internal walls
Cavity wall insulation
A borescope survey, then blown mineral wool or bonded bead injected into empty cavity walls.
Cavity wall extraction and refill
Failed, wet or slumped cavity insulation removed, wall ties checked, then refilled.
Cavity wall tie replacement
Replacing corroded wall ties, often found during cavity extraction.
Cavity survey only
Borescope and thermal imaging to show whether a wall is empty, part-filled or failed.
Party wall cavity insulation
Filling cavity party walls to stop hidden 'party wall bypass' heat loss.
Narrow and hard-to-treat cavities
Specialist bead or wool systems for narrow, stone-faced, exposed or high-rise cavities.
Begin your project
Price breathable IWI for period homes in two minutes
See a price range for your property type, with grants and 0% VAT applied where they fit. A survey always confirms the final figure.