menu:
Solid wall insulation – what’s it all about?
If your home was built before or around 1920, its external walls are likely to be solid rather than ‘cavity walls’. Cavity walls are made of two layers with a small gap or ‘cavity’ between them. This cavity acts as a barrier to reduce heat flow through the wall
Solid walls have no such gap and this allows more heat to pass through them than through cavity walls. In fact, twice as much heat can be lost through an un-insulated solid wall as through an un-insulated cavity wall.
But the good news is that, like cavity walls, solid walls can be insulated – from the inside or the outside
Why insulate your solid walls?
Solid wall insulation is an effective way to stop wasting energy and money at home. In winter, a well insulated house keeps warmth exactly where you need it – indoors.
So, insulating your walls will help to heat your home more efficiently. Using less energy reduces carbon dioxide (CO2): one of the biggest causes of climate change. It will help you to stop wasting money on your energy bills too.
What could you save?
Solid walls can be insulated in two different ways: with internal insulation (from the inside) or external insulation (from the outside). Both options can make your home warmer and more comfortable, and greatly reduce your heating bills at the same time.
In fact, by insulating your solid walls you could cut your heating costs by up to 40%. By using less energy, your household will produce less CO2. So, insulating your walls is a great way to help fight climate change.
Cavity walled properties can also benefit from the same kind of solid wall insulation, especially if the cavities are not suitable for filling – always check the best option with your installer.
Let’s do the maths
| Type of solid wall insulation | Saving per year | Total cost including installation | CO2 saved per year |
|---|---|---|---|
| Internal | Around £380 | £5,500 - £8,500 | 2 tonnes |
| External | £400 | £10,500 - £14,500 | 2.1 tonnes |
*Estimated figures based on insulating a gas-heated, semi-detached home with three bedrooms.
The figures given above are for the whole installation however if you are going to be renovating the individual walls of your home, you can make some big savings by insulating them at the same time.
Is solid wall insulation suitable for your home?
Internal wall insulation is best carried out when you are re-plastering your walls or you’re changing major fittings in your bathroom or kitchen. External wall insulation will be more cost effective if your external walls need re-rendering; you may need planning permission if your property is listed or located within a conservation area. Each approach has its own pros and cons; conditions when it’s ideal or which make it unsuitable.
Did you know…? 1 in 4 homes in the UK has solid walls
How do you get solid wall insulation?
Internal solid wall insulation is usually installed professionally, and should not be attempted by the average DIY-er; only the very experienced should install it themselves. Approach an installer that provides dry lining or plastering and ask them to show you:
1. examples of previously completed internal wall insulation work
Ask them what internal wall installations they have done previously and if they have any photos of the work before, during and after.
2. what is the best way of insulating your walls to achieve a good energy performance (it should be to a U-value of around 0.35W/m2K)
The U-value of a wall is a measure of the rate at which heat passes through the wall and so is a measure of how well insulated the wall is and is expressed in terms of “Watts per meter squared-Kelvin” (W/m2K). The lower the U-value, the better the performance of the insulation and the less it will cost to heat your home.
3. what measures can be taken to prevent condensation forming on the wall structure once it is insulated.
Condensation occurs when warm air meets a cold surface. This means that when internal wall insulation is fitted heat is prevented from reaching the wall of your home, which whilst good news in terms of preventing energy from being wasted, also means there is a risk of unwanted condensation. To prevent this from happening a special seal, which prevents warm moist air from reaching the wall, is fitted as part of the solid wall installation process.
How does solid wall insulation work?
Heat will always flow from a warm area to a cold one. In winter, the colder it is outside, the faster heat from your home will escape into the surrounding air.
Solid wall insulation slows down the rate at which it escapes, keeping as much of it as possible inside your home for as long as possible. How? Insulation works by coating or filling walls with a layer of material that only allows heat to pass through it very slowly. This reduces what is known as the U value of the walls – the rate at which heat can flow through them. The lower the U value, the more slowly heat is lost – and the more money you will save on your fuel bill to keep your home warm.
Solid wall insulation also helps prevent “cold bridging”. Cold bridging occurs when a material that is a good conductor of heat makes a “bridge” between the warm interior and the cold exterior. They are a significant source of heat loss and can lead to condensation and mould forming in buildings. An example of a cold bridge would be the party wall separating two semi-detached homes and spanning the length of the building. Warmth from both homes is conducted along the length of this wall and escapes into the air.
You may on occasion also see references to the “thermal conductivity” of the insulation material. This is often known as the “lambda (?) value” and is measured in “watts per meter-kelvin” (W/mK). The thermal conductivity of a material describes how easily heat passes through it. The best insulation materials have a low lambda value as a material with a low thermal conductivity will need a thinner layer than a material with a high thermal conductivity.
External wall insulation can also renew the appearance of the house, improve weatherproofing, air tightness and sound resistance.
How to identify whether I have solid walls?
If your home has solid walls, then it should be suitable for either external or internal insulation. That said, each measure comes with its own pros and cons; conditions when it’s ideal or which make it unsuitable. To find out what might be suitable for you read the section on ‘ How do internal and external solid wall insulation compare?’. Once you have decided on the type of insulation, speak to your installer about whether this is the most suitable option for your home.
Does your home have solid walls?
Solid walls are mainly made of brick or stone and are found in most houses built before the 1920s. So, if your house dates back to Edwardian, Victorian or Georgian times – and is built of brick or stone – its walls are likely to be solid.
The easiest way to tell is from the pattern of the bricks on the outside of your house.
If your home has solid walls, the bricks will tend to be placed head-on and lengthways in an alternating pattern like this.
If your home has cavity walls, the bricks will tend to have a regular pattern like this.
If the brickwork has been covered, you may be able to tell a solid wall by measuring its thickness. Go to a window or door on one of your outer walls, and take a measurement there. If the wall is more than 25.4cm thick then it probably has a cavity; solid brick walls are usually around 22cm thick; solid stone walls are just a little thicker.
You can also contact your local authority’s building control department, which might know if your house has solid walls.
Solid wall insulation can also work for properties with cavity walls that are not suitable for cavity wall insulation and other non-traditional housing types.
How do internal and external solid wall insulation compare?
Both internal and external solid wall insulation substantially reduce a home’s heating costs and CO2 emissions. However they are quite different in terms of the effect they have on your home:
Internal Wall Insulation
• Generally cheaper to install than external wall insulation
• Doesn’t alter the appearance of outside walls but it will slightly reduce the floor area of any rooms in which it is applied (the thickness of the insulation is typically around 100mm).
• Is ideally installed at the same time as internal renovation work and re-plastering as this will reduce the costs of the installation.
• As work is being done to the interior of the house, there will be some disruption but the disruption can be minimised by doing it room by room.
• Skirting boards, door frames and external fittings need to be removed and reattached to the new wall surface.
• Can make it difficult to fix heavy items to inside walls – although special fixings are available to help.
• If there are unresolved problems with penetrating or rising damp, these should be resolved before installation.
External wall insulation
• Can be applied without disruption to the household and does not reduce the floor area of your home.
• Renews the appearance of ageing outer walls. Planning permission may be required so check with your local council before undertaking any work.
• Fills cracks and gaps in the brickwork, which will reduce draughts.
• Increases the lifetime of a home’s wall by protecting the brickwork.
• Reduces condensation on internal walls and can help prevent damp, although it will not solve rising or penetration damp which must be resolved prior to insulating the walls.
• Is ideally installed at the same time as other refurbishment work to outer walls as this will save you a lot of money.
• Requires good access to the outer walls so that the installers can apply the insulation.
• Not recommended if the outer walls are structurally unsound and can not be repaired.
source:
www.energysavingtrust.org.uk