PROJECT PLANNING
ALL YOU NEED TO KNOW ABOUT THIS INSULATION, FROM WHETHER YOU NEED IT, TIPS FOR INSTALLING AND THE TYPES TO USE
T here are many benefits to having cavity wall insulation (or CWI). According to the Energy Saving Trust (energysaving trust.org.uk), uninsulated walls account for almost a third of the heat lost from a home. So fitting cavity wall insulation is a great chance to slash your energy bills and save energy. It’s also one of the most cost-effective and longlasting upgrades you can make.
Modern masonry homes are built with cavity walls, which typically feature an inner blockwork wall, a cavity and an outer wall of brick or rendered blockwork. The gap in between the layers is filled with energy-saving insulation to Building Regulations standards.
Older houses might have cavity walls but no insulation, resulting in a colder property that is not as energy efficient as it could be. Thankfully, existing cavity walls can be filled with insulation without needing to be rebuilt.
‘Most of a home’s energy is used in space heating and if you don’t have good structural fabric, you lose heat through walls,’ says Simon Storer, chief executive, Insulation Manufacturers Association (insulationmanufacturers. org.uk).‘Most properties built after 1920 have a cavity wall, and most after 1990 will have insulation in it. Houses built before 1920 usually have a single-skin brick wall, with no cavity. These homes can only be treated with external or internal wall insulation.’
WHAT ARE THE BENEFITS?
Upgrading insulation is the foundation for creating a more energy-efficient house. This is known as a fabric-first approach. ‘It’s very important to make the insulation in your home as good as it can be,’ says Simon Storer. ‘Invest in making the building fabric efficient before spending money on hi-tech solutions, such as solar panels and heat pumps.’
Consider engaging an independent energy assessor to help you develop a short and long-term plan for improving your whole property’s energy efficiency. ‘You’ll get the best benefits if cavity wall insulation is part of a wider plan for the whole property to reach the best energy efficiency possible,’ says Nigel Donohue, chief executive at the Insulation Assurance Authority (theiaa.co.uk).
WHAT TYPES ARE THERE?
Blown mineral wool This is forced into cavity walls to form an energy-efficient insulating layer. It’s cost-effective and offers good performance. Cavities need to be clean and free from obstruction, otherwise the insulation may get caught and not fill the void correctly.
Polystyrene bead This method involves blowing small balls of expanding polystyrene insulation (EPS) into existing cavity walls through small holes. Beads are quick to install, perform well and don’t absorb moisture. ‘One advantage is that a long nozzle can be used that shoots
