Cavity Wall Insulation - FAQ

How long does the installation take?

Generally speaking the installation process takes around 2-3 hours, but longer if the property is particularly large.

Are there any known problems with cavity wall insulation?

Very few these days. However, when the process was in its infancy some years ago, many installers used a material known as Urea Formaldehyde. This material sometimes helped the transfer of water across the cavity, resulting in damp patches forming on internal walls. These days Urea Formaldehyde is rarely used, installation techniques and materials have improved considerably.

If the external wall appears damaged or there are objects in the cavity that may allow water to cross from the external wall to the internal wall, repairs must be carried out before the installation can happen. In addition all materials must be water repellent and all installations now carry a 25 year independent (CIGA) guarantee.

Does cavity wall insulation cause damp?

Condensation is a result of the warm moist air found in the house coming into contact with cold surfaces, such as the external walls. The warm air cools against the cold surface and deposits the water that it can no longer retain. Cavity wall insulation will ensure that these surfaces are not cold and will therefore not encourage condensation to form.

However, before insulation can be installed a detailed survey must be undertaken to identify areas with damp or at risk of damp developing. Your surveyor will advise on what, if any, remedial work may be required before the cavities can be insulated.

Can cavity wall insulation be installed in all properties?

Most properties built after 1920 have cavity walls and provided that they are sound, have an effective damp proof course and are of traditional masonry construction (built with bricks and/or concrete blocks), are suitable for the installation of cavity insulation. There are, however, some properties with cavity walls that cannot usually be insulated including timber frame, steel frame, system built (common for social housing), or where there is a ‘chemical damp proof course’.

If the mortar joints or the wall ties located within the cavity are in poor condition then remedial work may be required prior to the insulation being installed. Exposed brick walls of properties in very exposed locations subject to driving rain, also require special consideration. However, if in doubt installers are always happy to survey a property without obligation, to assess if it is suitable.

What is cavity wall insulation made of?

Mineral Wool Fibre which is treated with water repellant and made from either molten rock spun out like candy floss and then chopped up to be blown into the cavity or the more familiar glass fibre similar to that used for insulating lofts, again chopped up and blown into to the cavity. Both of these types of mineral wool are know by different trade names but for insulation purposes they behave in the same way and have very similar insulating qualities.

Polystyrene Beads which are very similar to the beans found in bean bags but have an adhesive applied when installed into the cavity to stop them being distrupted if any later work is carried out on the property such as replacing doors and windows .

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