External wall insulation: creating a more attractive, warmer and quieter home

19 May 2023
5 min read
External wall insulation being installed

It’s an investment for the long term but one of our team members, Sue Amiel, took the decision to install exterior wall insulation at her family home in Bristol and is now enjoying many benefits. Here Sue explains what the process was like, the costs and how it has made a difference.

Original exterior before insulation has been installed.

We had been considering exterior wall insulation as we knew it would greatly improve the energy efficiency of the house.

Our home is a 1930s four-bedroom semi-detached property with a gas central heating system that was installed around seven years ago. I live with my husband and two children. We have done quite a lot of work to make it less draughty and keep the heat in. This has included draught proofing around doors and windows and secondary glazing on our original wooden windows at the front of the house.

Our exterior walls were the original pebbledash and there were quite a lot of cracks so we knew we had to tackle those as there was the risk of damp getting in. We had been considering exterior wall insulation as an option for some time as a solution to the damaged walls and we knew it would also greatly improve the energy efficiency of the house.

A helpful recommendation for finding a solid wall installer

Our neighbours across the road had recently had external wall insulation installed and the company did an excellent job so this inspired us to take the plunge. We were fortunate in that we managed to get a lot of the cost covered through a Government subsidy. Sadly, this no longer exists and homeowners need to pay for the work themselves now.

Finding a company that you trust was half the battle so having a recommendation made the decision a lot easier. We used Elite Rendering Systems and were really pleased with their work. A good place to start if you are looking for installers is the TrustMark website, where you can find tradespeople who have signed up to this Government endorsed scheme.

My experience of wall insulation

Thermal blocks used for external wall insulation

It wasn’t noisy or disruptive and we were able to carry on with our usual activities, undisturbed.

The principle is simple – foam blocks, 100mm in depth, are fixed to all the walls on the property and then a render is applied. It’s a bit like covering your home with a big water-resistant blanket.

From start to finish, the work took around four weeks. Scaffolding was required to cover the whole house but the company organised this. It wasn’t noisy or disruptive and we were able to carry on with our usual activities, undisturbed.

There were some minor adjustments that had to be made to account for the fact that the walls were now deeper. The installer extended our window sills and, although they are plastic rather than the original wood, they are very good quality and look in keeping with the windows. The roof also had to be slightly extended so that there is an adequate overhang. This was very straightforward and was done before work commenced.

For me, the best bit was choosing the render colour! There is a huge choice of colours and we opted for a pale powder blue which is so much more attractive than the brown pebbledash that we previously had.

Costs and savings from wall insulation

House exterior while insulation is being installed

It’s difficult to give cost comparisons because energy prices have risen so much in the last 12 months which makes it difficult to give a meaningful before and after picture of how the insulation has saved us money. However, our energy bill for the last 12 months (January to December 2022) was £1,970 for electricity and gas (£822 for electricity and £1,148 for gas) – that’s around £164 per month. This is without the discount that all households received through the Government Discount Energy Bills Support Scheme. Our most expensive period, unsurprisingly, was mid-November to mid-December which cost £245 in gas and £112 in electricity.

When I compare these figures to Ofgem’s estimated average energy bill costs, our annual bill was more on a par with the lowest energy usage household – a flat or a one-bedroom house. Ofgem estimates that a household of our size will typically pay £2,900 and £4,300 per year so that’s a pretty big cost saving of something between £930 and £2,330 in just one year.

Additional benefits of wall insulation

House exterior after wall insulation install has been completed

We have also found that the house retains its heat for a lot longer than it did before – even during several very cold snaps. We are able to just turn on the heating for a short while – 30 or 60 minutes at a time and this can keep the house warm for the rest of the evening.

Another surprising benefit is that the house is insulated from sound too so we are noticing that it’s quieter. One of the major benefits for me is the markedly improved appearance – the house looks so much smarter than it did and I think will have more kerbside appeal to prospective buyers if we decide to sell.

External wall insulation does add up

The Energy Saving Trust says the typical installation cost of external wall insulation on a three-bedroom semi-detached house is around £12,000. It’s a big investment.

But for homeowners who aren’t planning to move house during the payback period (the period of time required to recoup your investment), it’s a good option. It’s important to make sure that you have insulated as much as you can on the inside before turning your attention to the outside walls. Around 35 per cent of all heat loss in the home occurs through the walls so this is a great way of protecting yourself from rising energy costs and reducing your CO2 emissions.


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Man installing wall insulation - photo by Michael Baird