Insulating solid walls

Last updated Wednesday 30 April 2008

Extra layers to beat the cold

Solid they may be, but when it comes to keeping the heat in, the walls of old houses may not be so steady. Add insulation inside or out to stay snug and slash bills.

Modern houses typically have two layers of brick with a gap - or 'cavity' - in between, which can be filled with insulating material. Houses built before 1930 are more likely to have solid walls that leak more heat. In fact, almost half of heat lost in an uninsulated home goes through the walls. Insulating solid walls is one of the biggest savers ofCO2, and money, there is. Grants are available to help with upfront costs and you'll soon see a huge reduction in your monthly energy bills.

Read more below
Photo: Insulating solid walls

Saves 2400-2640kg of CO2 per year

135 Bloomers are doing this

CO2 reduction 4 out of 5

Cheapness 5 out of 5

Popularity 2 out of 5

Cost £1,900 - £3,000

About these ratings

In this article:

How will it make a difference?

Pub Fact

  • Constructing, occupying and maintaining buildings creates around 50% of the UK's total CO2 emissions
  • The amount of heat lost in homes annually through roofs and walls is enough to heat three million homes for a year
  • Standing for nearly 2000 years, the Pantheon Temple in Rome has a 43m central dome made from lime plaster

Heating our homes is one of the most energy hungry things we do, so good insulation is one of the best ways to reduce our emissions.

  • If everyone insulated their solid walls, it would save a massive 16 million tonnes of CO2 - equivalent to the emissions of 2.7 million homes for a year
  • Internal insulation will reduce heat lost to the outside walls by around a quarter and save around £300 off your energy bill a year
  • Solid wall insulation can reduce heat loss through the walls by as much as 80%
  • External insulation also saves around £300

Back to top

What's the debate

External insulation uses cement, a material responsible for up to 10% of global CO2: that's even more than the much-criticised aviation industry. Lime-based cladding dramatically lowers the CO2 impact and won't be as prone to damp as concrete. (See related links for different lime products.)

Back to top

How do I do it?

  • There are two options for insulating solid walls: adding a layer to the outside of your house or to the internal walls. Which one's right for you depends on your house and your budget. See the table below for the pros and cons of each
  • Don't know when your house was built? Check the brick pattern to see whether you have solid walls. Solid walls have alternate shorter bricks (bricks set at right-angles to the rest) whereas cavity walls do not
  • Make sure your contractor is approved by the External Wall Insulation Association, or the National Insulation Association for internal insulation
  • See the Energy Saving Trust: Solid wall insulation for more information and an in-depth guide on how to do it
Internal and external insulation compared
Works by layering thick (9cm) readymade plaster boards over the walls inside your house, or rolls of insulation encased in wooden battens Works by layering a weatherproof insulation (made from waste wood chipping formed into boards) to your outside walls, rendering in with cement or lime cladding with a protective finish over the top
Up to three times more expensive than external, but saves similar CO2 each yearIt's cheaper than internal and pays back within six years
An experienced DIYer can install it themselves, but it's a major disruption to the houseRequires professional installation and scaffolding
Lose around 1% of internal space (more in small rooms) so best if your rooms are spaciousYour house will stick out from uninsulated houses nearby and planning permission may be required in some cases
Outside walls can suffer because they are still exposed to bad weather but no longer being dried out by heat escaping from insideOnly suitable for flats if all of them are insulated and often only suitable in conservation areas if you use lime based cement
Will need to relocate plug sockets, radiators and fitted furnitureMost suitable when combined with house renovations such as renewing the cladding on your outside walls, otherwise it's very expensive

Back to top

What's stopping me?

"It sounds expensive and a lot of faff"

It can be expensive, but there are grants of about £500 available. With money saved on heating bills external insulation will pay for itself within six years and internal insulation in about ten.

In an ideal world, to minimise disruption you'd have internal insulation put in before moving into a new house. If you already have cladding, add external installation when your outside walls are due for re-cladding anyway.

Back to top


If you like this action send it to a friend

Share this

Back to top


Theresa, Suffolk 2009-05-30

I'm still investigating this for my tiny victorian mid-terrace house and to be fair the reduction in room size will only affect three walls, one in each of three rooms. But i'm wondering how effective growing vegetation up the external walls will be - it would reduce the wind and weather directly on the bricks, with any cooling effect that would have. I've already got Ivy on 50% of the front NW facing wall and am considering overgrowing that with clematis and honeysuckle and adding a cllimbing hydrangea to the uncovered part. Have there been any trials done?

BAZ, Shrewsbury Shropshire 2009-01-08

In my previous home, a 1939 detached solid wall brick built house, I was having terrible condensation problems beind furniture and in corners.
i solved the problem completely by fitting an extract hood over the cooker and insulating the external wall as follows.
From floor to ceiling fix, vertically, 50 x 25mm tilers lath to the walls at 600mm centres. Fix with adequate screws and plugs at 600mm centres.
Using 25mm thick insulation board, fill in the gaps between the lath, now is also the right time to alter the electrical installation.
Over the whole wall fix with staples to the battens a PVC sheet which will act as a VAPOUR BARRIER.
Now cut and fix wallboard 12mm thick using 25mm galvanised plasterboard nails or screws.
Tape joints and skim to a finish.
Job done
This is also very useful if your existing plaster has degraded, DON'T PULL IT OFF, just overboard.

The Bloom Team, London 2008-09-10

Hi Flora. Solid wall insulation falls under the CERT programme but to date there havenít been many installations because you get bigger savings for a given amount of cash from cavity or loft insulation. Unfortunately this doesnít help people with solid wall homes much and their energy bills are much bigger to boot. It's worth checking out EST's Grants Information Database ( and helpline (0800 512 012) for more information. All the best, The Bloom Team

flora 2008-09-05

I have tried every source available and I cannot find grants for solid wall insulation. Please publish details if you have found them - more than half the homes in Brfitain have solid walls, and they are currently being left out.

Flower representing the 'Insulating solid walls' action

People using this site

2% of Bloomers are doing this action

Less than 1% of women aged between 16 and 20 are doing this action.

Top 3 popular actions that females aged 16-19 are doing

More about actions by people of this age and gender.

Latest actions on Bloom

Latest related BBC News stories

RSS icon | News feeds | View all stories

Latest related BBC audio and video clips

View all clips

Related links

Elsewhere on the web

Related links open in a new window. The BBC is not responsible for content on external sites.

Browse all actions

Glossary terms used on this page
CO2, or carbon dioxide, is made up of the elements carbon and oxygen. It exists quite naturally in our atmosphere, as part of the carbon cycle. Everyday processes in the plant and animal world both add CO2 to the atmosphere and take it out. However, because it is a greenhouse gas - meaning it affects the temperature of the earth - the exact level of CO2 is important. Burning fossil fuels releases CO2 into the atmosphere, hence the anxiety that extensive use of these fuels is causing climate change.
Cavity walls
A wall comprising two layers of brick or block separated by a cavity (gap). This air space acts as an insulator, but does so more effectively if filled with an insulating material, such as plastic foam or natural materials like wool or recycled newspaper.
Emissions are the CO2 (and other greenhouse gases) produced by energy use, usually calculated and stated as an annual tally: also referred to as your carbon footprint. Your personal emissions can be direct - such as the gas you personally use to heat your home or the petrol you burn to power your car - or indirect - meaning the energy use that has gone into the products or services you buy. The latter, such as the emissions caused by the manufacture of your new TV, or the packaging your food comes in, are also referred to as embodied emissions.
Planning permission
Planning permission is consent, usually from a local council, to build on land, or change the use of land or buildings. Significant structural change, such as that often associated with microgeneration projects, is likely to require planning permission. Changes to listed buildings require additional, separate consent. navigation


The BBC is not responsible for the content of external sites. Read more.

This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.