In this blog, we explore how cavity wall insulation, when correctly fitted, helps prevent moisture penetration and regulates wall temperatures, rather than causing damp issues.
Does cavity wall insulation cause damp?
Estimated reading time: 2 minutes
The simple answer is no.
The real causes of damp
Cavity wall insulation does not cause damp or condensation leading to mould growth in properties.
Common causes of damp and condensation after insulation installation typically include:
- Insufficient ventilation
- Neglected property maintenance
- Poor construction supervision and practices
- Substandard building remedial work
Additionally, poor practices before and during the insulation installation process can worsen damp or condensation issues.
Since the introduction of cavity wall insulation in the UK, many companies have failed to adhere to the high standards required for installation, whether in newly built homes or existing properties requiring retrospective insulation. These substandard practices have led to, and continue to cause, issues such as condensation on walls due to voids in the insulation, or dampness resulting from debris left within the cavity.
It is essential to ensure that cavity wall insulation is installed in accordance with industry standards to prevent such problems and to maintain the long-term integrity and energy efficiency of the property.
A thorough survey is mandatory
A professional assessment or survey of every property must be carried out before cavity wall insulation (CWI) is installed to rule out some of the common causes of post-installation issues. This survey must determine whether the property can and should be insulated.
As a minimum, the following aspects should be assessed:
- Whether the property is of traditional cavity construction.
- Whether the construction is appropriate for the locality and its exposure.
- Whether the structural integrity of the building is intact.
- Whether the render or pointing is in good condition.
- Whether the width of the cavity complies with the insulation system to be installed (it usually needs to be greater than 50mm).
- Whether water dispersal systems are adequate and functioning properly.
- Whether the Damp Proof Course (DPC) is visible and at least two courses above ground level.
- Whether the ventilation for combustion appliances is compliant and adequate.
- Whether the cavities and wall ties are clean and free from obstructions.
The above list is not exhaustive but covers most of the critical checks. A professional cavity wall insulation company with trained and qualified assessors will identify and inform the homeowner of all issues before any insulation is installed.
Any identified defects must be rectified either before or after the insulation is installed. For example, cavity cleaning should be completed prior to the installation of new insulation, whereas repointing is typically carried out after the insulation process to avoid damaging newly re-pointed walls.
Are there areas in the UK where cavity wall insulation cannot be installed?
Most cavity wall insulation systems in the UK are approved for use nationwide. The exception is urea formaldehyde foam, which faces restrictions in certain regions and construction types. However, regardless of the insulation type, properties must comply with the necessary survey criteria to ensure suitability for installation.
Ventilation
Whether or not cavity wall insulation is installed, proper ventilation is essential to maintain healthy air circulation within a property. Mechanical ventilation is crucial in wet rooms, such as kitchens and bathrooms, to control air movement and prevent moisture buildup.
Background ventilation in all rooms, such as trickle vents in windows or simply opening windows, is highly effective in reducing condensation and maintaining indoor air quality.
Summary
Cavity wall insulation (CWI) is a valuable solution for improving energy efficiency in homes, but concerns about dampness often arise. The truth is that properly installed CWI does not cause damp or condensation issues. Instead, common causes of dampness include inadequate ventilation, poor property maintenance, and substandard construction practices.
A thorough professional survey is essential before installation to ensure the property is suitable for insulation and meets necessary criteria such as structural integrity, cavity width, and water dispersal systems. Failure to follow industry standards during installation can lead to issues like condensation or dampness.
While most CWI systems are approved for use across the UK, some insulation types, such as urea formaldehyde foam, have regional restrictions. Additionally, adequate ventilation—both mechanical and background—is crucial to maintaining air quality and preventing moisture buildup in all properties, regardless of insulation.
By following best practices and working with qualified professionals, homeowners can enjoy the benefits of CWI without the risk of damp-related problems.
