Insulation

Cavity Wall Construction

This article is provided by H+H

Cavity wall construction was introduced into mainstream UK housebuilding in the 1930s and most modern houses are now built with cavity walls. Since the concept has been around for approaching 100 years, the materials used to build such walls have developed hugely. A modern cavity wall provides a watertight, highly insulated external wall structure.

What is a cavity wall?

Cavity walls are used to build the external walls of houses. They consist of two layers – or leaves - of building material with a layer of insulation in between. 

The outer leaf is essentially a decorative facing material, usually made of brick.  It helps to keep the rain out, whilst also adding to the wind load resistance of the complete wall. To make sure the entire wall structure is stable, the brick outer leaf will be "tied" to the inner block leaf with wall ties. These are plastic or metal ties that are permanently fixed into the mortar of both brick and block.

In between these two masonry leaves will be a gap - typically around 100 millimetres (mm) - which is normally filled with insulation material.  The insulation material can be of various types, including mineral wool or PIR.

What are the advantages of a cavity wall?

Cavity walls were originally introduced to stop rain seeping through solid brick walls. In the damp climate of the UK this is an important precaution. Towards the end of the 1900s, the cavity became a focus for insulation, used to improve the thermal performance of structures and the energy efficiency of buildings.

New houses have standard designs for cavity walls, ensuring there is sufficient insulation to give the thermal performance required. The resulting external wall structure, including brick, insulation and block will be around 300 millimetres (mm) wide.

A well designed cavity wall will be completely watertight, airtight and very thermally efficient, ensuring that the house does not lose heat through the walls during the winter. If walls are made of masonry materials – using the traditional brick and block method – then they will also help to keep a house cooler during the summer.

What is cavity wall insulation?

In a modern house, the external walls will be designed to include insulation. Older properties, typically those built in the 1950’s, 1960’s and 1970’s, are likely to have been built with cavity walls which did not originally include insulation.  A popular home improvement measure in these instances is to fill the cavity with insulation. This can make a huge difference to the energy efficiency of the house but needs to be done by an expert, since if it is not done properly the process can cause problems.

Home insulation

Including effective insulation in the structure of a home is the most efficient and cost-effective way to achieve an energy efficient home that is both comfortable and cheap to run.  Cavity walls constructed from robust masonry materials remain the most popular choice.

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