External Wall Insulation Problems: Damp, Mould & Solutions

What is External Wall Insulation (EWI)?

External Wall Insulation involves fixing insulation boards to the outside of a property, then covering them with render or cladding. It was promoted heavily under government schemes (ECO4, GBIS) as a way to improve energy efficiency in solid-walled homes.

Why Does EWI Cause Damp Problems?

The NAO report identified several reasons why external wall insulation fails:

1. Traps Moisture

EWI creates an impermeable barrier that prevents walls from "breathing." In traditional solid-walled homes, moisture naturally evaporates through the brick. EWI traps this moisture, leading to:

• Damp penetration into interior walls
• Mould growth on internal surfaces
• Deterioration of the underlying wall

2. Installation Defects

Many installations suffer from poor workmanship:

• Inadequate surface preparation
• Poor sealing around windows and doors
• Insufficient damp-proof course protection
• Inadequate ventilation provisions
• Thermal bridging at junctions

3. Wrong Property Type

EWI was often installed on unsuitable properties:

• Victorian/Edwardian homes designed to "breathe"
• Properties with existing damp issues
• Buildings in high-moisture environments
• Homes without adequate ventilation

Common EWI Problems

Damp and Mould

• Black mould on interior walls (especially corners and behind furniture)
• Damp patches that worsen in winter
• Musty, unpleasant odors
• Wallpaper peeling
• Paint discoloration and bubbling

Condensation

• Excessive moisture on windows
• Water streaming down walls
• Wet window sills and frames
• Mould growth around windows

Structural Issues

• Crumbling render or cladding
• Cracks in the insulation system
• Water ingress behind the insulation
• Damage to original brickwork
• Timber rot in window frames

Health Impacts

• Respiratory problems (asthma, bronchitis)
• Allergic reactions
• Skin irritation
• Eye problems
• Increased infections

Warning Signs to Watch For

If you have EWI, watch for these early warning signs:

1. Musty smell when entering rooms
2. Black spots appearing on walls or ceilings
3. Increased condensation since installation
4. Walls feeling cold or damp to touch
5. Peeling wallpaper or paint
6. Visible cracks in external render
7. Discoloration of external finish
8. Health issues (coughing, sneezing) that improve away from home

Solutions and Next Steps

Immediate Actions

1. Document everything:
   • Take dated photos of all problems
   • Keep records of when issues started
   • Save all correspondence
   • Note any health impacts
2. Improve ventilation:
   • Open windows regularly
   • Use extractor fans
   • Consider dehumidifiers (temporary measure)
3. Contact installer:
   • Report problems in writing
   • Request inspection
   • Ask about warranty coverage

Professional Assessment

Get an independent survey to assess:

• Extent of moisture penetration
• Quality of installation
• Underlying wall condition
• Recommended remediation approach
• Estimated costs

Remediation Options

Depending on severity, options include:

• Repairs: Fix specific defects (cheaper but may not solve root cause)
• Enhancement: Improve ventilation and breathability
• Removal: Complete removal of EWI system (most effective but expensive)

Costs

Typical costs for EWI remediation:

• Independent survey: £300 - £800
• Minor repairs: £2,000 - £5,000
• Complete removal: £8,000 - £25,000
• Alternative insulation: £5,000 - £15,000

Compensation Claims

You may be entitled to claim compensation from:

• Original installer: Poor workmanship or breach of warranty
• Trustmark: Inadequate quality assurance
• Government scheme: Scheme design failures

Compensation can cover:

• Survey costs
• Removal and remediation
• Property damage
• Health impacts
• Temporary accommodation (if needed)
• Loss of property value
• Distress and inconvenience