internal wall rockwool insulation

Wall and floor insulation guide

Ways to create a comfortable and quiet home, and reduce your energy costs

By Ifeoluwa Adedej | 8 October 2021

Installing wall and floor insulation can be the key to a warmer, more energy-efficient home. Between one third and two thirds of the heat loss in the average UK property can be attributed to the walls. Insulation ensures that the property maintains a comfortable temperature and reduces energy costs.

Finding a competent professional who can advise you on the most suitable materials for your property is a good first step in the process. Organisations such as the National Insulation Association and the Cavity Insulation Guarantee Agency, or the British Board of Agrément provide good advice.

Cavity wall insulation

If your home was built between the 1930s and 1980s, it may have cavity walls that lack insulation. Insulating material such as mineral wool can fill the cavity to prevent convection and heat loss.

‘The installer drills small holes, around the size of a 10p coin, at intervals in the outside wall of your home. Special equipment then blows insulation into the cavity,’ explains Neil Marshall, head of the National Insulation Alliance. ‘Once all the insulation is in, the installer fills the holes. The process takes a couple of hours.’

Before starting the work, submit a building notice to your local council. This is something the company carrying out the project can do for you. Expect to pay from around £725 for a detached four-bedroom property, or about £475 for a semi-detached property, according to the Energy Saving Trust.

 Cavity wall wool insulation Installation

Installation of cavity wall insulation by Knauf

Insulating solid walls

Solid wall construction, common in properties built before the 1920s, gives you the chance to overhaul the appearance of your home. You will need to seek permission from your local authority first, especially if you live in a designated area. You can expect to pay from £9,000.

‘External wall insulation is the best option for retrofit from a practical point of view. You can address these works without any internal alterations,’ says Adam Jannece, managing director at JCJ Construction.

‘It improves the wall’s ability to withstand the elements and the insulation is fixed directly to the masonry structure. It protects the facade from any further weather exposure. In turn this will also stop any pre-existing penetrating damp.’

Solid walls can be insulated internally as well as externally, but you can expect a lot of disruption and the loss of some floor space on a renovation. While it’s easier to apply internal wall insulation on a new-build, there are solutions for a renovation. These may include building stud walls and filling them with insulating material, or by fitting thin rigid boards.

installing internal wall rockwool insulation

Installing rockwool insulation. Photo: bilanol / Adobe Stock

Heritage buildings

For some heritage buildings, solid wall insulation may cause issues. These buildings were built to be breathable, therefore impermeable insulation products may cause moisture issues. So, opting for natural insulation materials is the best choice for these buildings.

You need to think about how external and internal wall insulation will affect heritage buildings. It’s possible you will see the loss of historic detail. Though, specialist retrofit architects have experience in how to retain detail.