Solid wall insulation: cost, savings and installation

Installing solid wall insulation in your property will cut your fuel bills and carbon emissions, as well keep your home warm and draught free.

Insulating your walls will increase
the energy efficiency of your home

“Walls are a big cause of heat loss, so insulating them is so important to make your home energy efficient,” says architectural designer and TV presenter Charlie Luxton. In fact, an un-insulated home loses around 45% of its heat through the walls, says the Energy Saving Trust (EST). In the current financial and environmental climate, it is vital that we all cut our household carbon emissions and fuel bills - insulating your walls can help do just that.

How much can you save by installing solid wall insulation?

According to the EST, installing internal wall insulation can save you £365 a year in fuel bills and 1.8 tonnes of CO2. External wall insulation could save you £385 and 1.9 tonnes a year.

Do you have solid walls?

If your home was built before 1920, it will probably have solid walls made of either brick or stone; the EST estimates that one in four UK homes fall into this category. If your house was built after 1920 then it’s likely to have cavity walls instead, which means your home was built with an internal and external wall separated with an air filled gap to reduce damp. “If you have cavity walls it’s important to fill them with insulation,” Charlie points out. Cavity walls are a lot more energy efficient than solid walls; twice as much heat is lost through un-insulated solid walls than cavity walls, according to the EST. If you are unsure whether your home has cavity or solid walls, seek advice from a professional.

Preparing your solid walls for insulation

Property expert Michael Holmes advises: “When you are planning a project, always see whether you can improve or repair the structure of the building first – make sure that it’s warm, dry, weather tight and structurally sound.” So before you consider installing solid wall insulation, make sure that any repairs are carried out first and any damp problems are corrected. The interior walls should be even. It is less disruptive and more cost effective to carry out solid wall insulation when you are doing other refurbishment work, so plan carefully.

Internal wall insulation is a cheaper option

There are two types of solid wall insulation:

Internal wall insulation

Internal solid wall insulation is cheaper than external insulation but it can be disruptive as work is carried out inside your home. Charlie points out that: “Internal wall insulation is useful if you can’t install external insulation because you live in a listed building or something.” Installing internal wall insulation means you will need to clear the internal space; removing skirting boards, radiators and fittings. Insulation can be installed with a stud wall, which is a second wall fitted to the original one and filled with around 120mm of mineral fibre insulation. Rigid insulation boards can be used instead, with a thickness of around 60mm, or you can combine both techniques. Either way, this will reduce the floor area of your home slightly.

External wall insulation

External wall insulation is best for cutting
carbon emissions

“External wall insulation is the most ideal option for reducing CO2 emissions. It reduces temperature fluctuation so that it’s not too hot in summer or too cold in winter,” explains Charlie. External insulation is more expensive, as it involves fixing a layer of insulation to all exterior walls and then covering this with cladding or plaster work before applying your chosen finish. However, external wall insulation is less disruptive and can increase the life span of your walls. External wall insulation will also improve the look of your home as well as weatherproof it and offer sound proofing. Be careful to check whether you need planning permission to install external wall insulation; if you live in a listed building or conservation area this may be necessary.

How much does installing solid wall insulation cost?

According to the EST, external solid wall insulation can cost around £10,500 to £14,500 to install and internal insulation between £5,500 and £8,500. It is worth checking with your local council to see if there are any grants available to help with the cost of installing solid wall insulation. Under the government’s Green Deal, which has yet to come into effect, you could receive up to a £6,500 loan to go towards the cost of insulating your home.

Hire a professional who has experience and valid public liability insurance to install your solid wall insulation. Get several quotes before deciding who to hire. Choosing a contractor who is registered with an organisation like the National Insulation Association or the Insulated Render and Cladding Association is a safe bet.