Types of Cavity Wall Insulation

Types of Cavity Wall Insulation2021-02-12T15:08:25+00:00

The energy wasted in heating poorly insulated houses accounts for one quarter of the polluting greenhouse gases produced.

When designed and installed correctly full cavity fill insulation is usually the most cost-effective energy efficiency measure available for the existing housing stock, after loft insulation, where the cavity wall is confirmed as being in good overall condition, crack free, where the local wind driven rain exposure factors confirm its suitability for use and where external or internal access is not highly costly or otherwise problematic. It can generally be installed without major disruption to occupants and most manufacturers claim it should need no maintenance.

Fig 1. Cavity Wall Insulation – Complaints

Fig 2. Cavity Wall Insulation – Damp & Mould

For existing houses retrofit cavity wall insulation can be filled by blowing or injecting the insulation through the outer leaf.

There are three main types of cavity wall insulation materials in use today namely:

  • mineral wool (rock wool or glass wool), and

  • bonded or unbonded polystyrene beads

  • closed cell polyurethane.

  • A fourth option, urea-formaldehyde cavity wall insulation was popular in the 1970/80s but has fallen from use due to emission of formaldehyde gas. It has also been found to decompose within the cavity forming voids and pathways for rainwater to bridge the cavity and consequent penetration of the rainwater through the inner masonry leaf and formation of black mould on internal wall finishes.

It is imperative that the chosen type of cavity wall insulation (CWI) must be appropriate and be suited to the particular house construction, location and wind driven rain exposure conditions and be correctly installed if the benefits of being one of the best ways of reducing heat loss from existing buildings and reducing polluting greenhouse gases is to be achieved.

In addition, the cavity wall must be confirmed as being in good overall condition and crack free, and the full fill cavity insulation should only be installed in suitable cavity-built walls meeting the requirements of the Building Regulations restrictions.

Failure to get it right may cause significant damage to your property and may result in highly disruptive, time consuming and expensive scaffolding, cavity wall insulation extraction and removal costs.

Fig 3. Cavity Wall Insulation Extraction

Fig 4. Cavity Wall Insulation Extraction – removal of brick

Cavity wall insulation measures should be tested and assessed for compliance with the Building Regulation requirements and be the subject of a current valid independent third party UKAS accredited certification. Technicians employed by the installing companies should be trained and approved by the manufacturer systems suppliers.

If you have had cavity wall insulation (CWI) carried out on your home which has caused damp, black mould, or health related issues, etc, and may require to be extracted, and you require the assistance of a chartered building engineer please click here to contact us.