What is solid wall insulation?

If your house was built prior to the 1930s, the chances are that it will have solid walls – simply a solid layer of masonry bricks. Insulating your walls – regardless of whether they are cavity or solid (or even timber-framed) – is a great way to make your home more energy efficient. The insulation will minimise heat loss in the winter, saving you money on your heating bills. It will also stop your home getting too warm in the summer, helping to keep your home at a more comfortable temperature.

According to research, twice as much heat could be lost through an un-insulated solid wall as through an un-insulated cavity wall. However, the great news is that solid walls can be insulated, both internally and externally.

The science behind insulation

If hot air and cold air are partitioned by a wall, heat will transfer through the wall, eventually cooling the room until an equilibrium is reached (where the outside temperature is equal to the inside temperature). In reality this very rarely happens, because rooms tend to be heated; so as heat escapes through the wall, more hot air is supplied by your heating system, keeping it at a comfortable ambient temperature. If the thermal gradient is larger, for example on a cold and wintry day, the movement of the thermal energy across the wall will be accelerated.

Insulating a solid masonry wall helps to provide a thermal barrier, which helps to slow the movement of heat escaping out into the external environment.  Less heating is therefore needed to keep the house at the required temperature.

Types of solid wall insulation for your home

Both internal and external insulation are great at keeping your home warmer, lowering your heating bills and cutting carbon emissions. However, both solutions have a different impact on your home, which is explained in the following section:

Internal solid wall insulation

There are a couple of methods to insulate a solid wall internally, which are either to use a rigid insulation board or build a stud wall. We recommend you get a professional in to complete this type of work, and you do not undertake it as DIY unless you are very experienced. Internal solid wall insulation can be as thick as 100mm, so your room will ‘shrink’ wherever it has an external supporting wall.

Advantages of internal wall insulation

• Cheaper than external insulation
• No aesthetic change to the outside of your home
• Works well when the home itself is going through a process of internal renovation

Disadvantages of internal wall insulation

• Will reduce the room you have in the living areas by up to 10cm, depending on the materials used
• Won’t necessarily get rid of any damp problems, which need to be tackled separately

External solid wall insulation

For external wall insulation, you need to employ a professional and you also need to consider local building regulations. This is because this process involves covering the original brickwork and could significantly alter the current appearance of the property, making out of step with the local area. Once any planning permission has been granted, the home can be insulated using an adhesive material which is fixed to the wall, then plastered over.

The finish applied to the external wall can be any combination of texturing, painting, tiling, brick slips, masonry work and/or cladding.

Advantages of solid wall insulation

• Less disruption to the household, as the work is carried out outside
• Renews your home’s external appearance and increases the lifetime of the brickwork
• Complements other refurbishment work
• An opportunity to fill cracks and holes in the brickwork, which will help reduce draughts(see Draught Proofing for more information)

Disadvantages of solid wall insulation

• More expensive than internal insulation
• Planning permission may be required
• Any work needs to comply with local building regulation
• May not solve all damp issues
• Work is not recommended if the building is not structurally sound

Costs of solid wall insulation

• Around £100/m2.
• Additional costs for downpipes, gas pipes, boiler flues and dishes.
• Subject to render strength – additional cost to remove old/weak render.
• Potential requirement for scaffolding – around £15/m2.

Measuring the effectiveness of solid wall insulation

The R-value is the measure of thermal resistance used in the building and construction industry today. The higher the R-value, the better the insulating properties of a material – so you should be looking to insulate your house with materials displaying a high R-value. Confusingly, you may hear the word U-value also bandied around. This is exactly the opposite, describing the ability of a material to conduct heat, so you want your insulating material to have a low U-value.

Installing solid wall insulation

Interested in getting solid wall installation? Lucky for you, we work in partnership with EWI Store who specialise in external wall insulation systems! They have a great team who are always happy to help with your enquiries.

Ealing is a fairly central part of London and most of the houses there were built over 100 years ago, and most of these homes were constructed with solid 220mm brick walls. According to the Energy Saving Trust, uninsulated solid walls can account up to 35% of total heat loss, therefore addressing this area can make a big impact on the energy efficiency of the property.

The Elsley’s are benefiting from a much more insulated household, having installed external wall insulation to the back of their mid-terrace home. Most of you may think that mid-terrace properties are ok  in terms of keeping the heat as they only have two exposed walls  – while some of that is very true, as you can see the back of the house has in fact 3 exposed walls and if left uninsulated the heat just escapes and the property is not comfortable to live in.

Here, 100mm of Kreisel EPS solid wall insulation was used to insulate the external walls. The insulation boards stuck on with adhesive and are then mechanically fixed to the outside brick, held together by plastic caps. Once the boards are put in place they are then rendered over and finished with the waterproof top-coat.

The Elsley’s were pleased to have received some help from the Government grant, which was available to a limited number of applicants in 2014, with the rest of the project being self-funded.

According to the EPC report that was conducted before the installation date, the Elsley’s should save in the region of £200-£250 on their annual heating bills and as well as that should have a much cosier and warmer home.

The external 100mm solid wall insulation solution has been installed on this semi-detached property in Greenford, Middlesex. In this case, Mr Smith has benefited a little bit from the Government grant with the rest of the project being self-financed.

Many properties in this part of Middlesex and Greater London were built either in the late 1800s or early 1900s with solid brick walls, which means cavity wall insulation is not possible to do. Solid wall insulation can either be installed on the inside or the outside of the property, and the customer chose external due to space considerations and to maximise the benefits of the externally applied render solution.

Having the 100mm EPS Kreisel system solution installed, has brought the property up to a band D rating on the EPC register. Not only has it improved the energy rating, the external wall solution will on average save Mr Smith’s family nearly £400 on heating bills. With the property being cosier and warmer it is also now protected from weathering, as the silicon silicut render goes on top of the insulation to provide all these additional benefits.

The photos below show some of the stages of the installation installation process:

Applying Kreisel EPS insulation boards.

External solid wall insulation at the back of the property, Greenford London.

London has undergone many waves of house building, with each type of home creating their own energy efficiency problems and areas for improvement.

It was 1965, that Building Regulations introduced the first limits on the amount of energy that could be lost through certain elements of a newly built house. However even until very recently, building standards were not sufficient to create what we would consider an efficient property.

Most housing in London was built well before building regulations really took effect and therefore it is fair to say that the majority is poorly insulated and fitted with inefficient heating systems. Yet these are very fixable problems.

There are plenty of ways you can improve the efficiency of your home, whether it be a 1900 Victorian terrace or a 1980s detached house. We thoroughly recommend an energy consultation to work out what is best for your home, as each property really is different and there is nothing better than tailored and personalised advice.

Having said this, you can tell a lot about a house by its age. As such, we can make some recommendations on the best steps for your home. It goes without saying that loft insulation should be up to standard (270mm) before you look at anything else – it really is the number 1 way to make your home more efficient, but here are some other key things you might want to consider to help lower your energy bills:

Pre 1930 London Properties:

• Solid Walls – Seen on almost all Pre 1930’s homes, solid walls are very inefficient. You can insulate with either external or internal insulation and there is funding available to do so.
• Timber floors in the majority of the home with cold solid concrete floor kitchens – It is fairly typical on Victorian terraces to see floorboards in the main area of the property and solid concrete floors in the extension. You should draught proof your floorboards using Draughtex and look at floor insulation – although this may involve lifting up the floorboards.
• Sash windows – Large single glazed sash windows are fairly typical on homes built in this era. Sash window double-glazing is expensive, and there is usually a cheaper option like refurbishment or draught proofing. You can read more on this here. Remember, old properties like this typically have lots of chimneys, so make sure you have them blocked off or use a chimney balloon to cut out draughts here since these cold draughts can very quickly strip the home of any hot air.

1930’s London Properties:

• Cavity Walls – After 1930, cavity walls became standard. This is great news for you, because cavities are very easily insulated and can make a big difference to your bills – they are simply injected from the outside with cavity wall insulation.
• Suspended timber floors  – Most 1930’s homes have timber floors, which can be either insulated or draught proofed.
• Draught Proofing – Once again these homes could well be draughty so it is worth looking at getting your doors and windows draught proofed.

Post war 1945-70 London Properties:

• Flat roofs – This isn’t always the case, but flat roofs became popular post-war, and were rarely well insulated. If you have one, make sure you look into flat roof insulation, this process is not as easy as you might hope, however the Government are currently offering £550 cashback if you were to opt getting this insulation installed via the Green Deal scheme.
• System Built Houses – If you live in a prefab or a flat, you could be losing a lot of heat through the walls. You should look into wall insulation – this could be either cavity or solid wall.
• Flats / Mid-High Rise – Flats present their own problems because the envelope of your home includes other people’s property, although having said that, where you have a party wall with a neighbour there should be no heat loss, so actually if you are in the middle of a block of flats this may actually be an advantage in terms of energy efficiency.

1970’s London Properties:

• Single glazing / smaller windows – Many 1970’s properties have small single glazed windows. Secondary glazing may well be worthwhile considering here.
• Cavity Walls – After the 60’s regulations on new homes meant that some insulation was fitted as standard, but it is still worth checking your cavity walls, as these were generally not insulated.
• Watch out for old boilers / electric heating (off grid / now on grid but still with electric heating) – The 1970’s was a time of energy uncertainty. Some properties were built without a gas supply and therefore use electric storage heaters. Others have even more unconventional heating systems like back boilers, gas room heaters and electric ceiling heating that could be costing you money. Look at whether you can change to gas central heating or take advantage of the RHI for renewable heating such as heat pumps.

Modern London Properties:

If you live in a relatively modern house, your cavity walls should have already been filled, but there are a few things you can still look out for:

• Loft Insulation top-up – Usually these properties have some loft insulation, but it may be worth getting a top up. Building regulations in the 80’s and 90’s was nowhere near today’s standards, so you could still save a tidy sum by getting more insulation.
• Old Boilers / heating systems – Houses around 20 years old may still have the original boiler present. It is really worth switching over to a modern one and is likely to be the biggest way to save on a modern property.
• Renewables – If your home is otherwise up to standard, it may be worth looking at renewable energy. Modern homes are likely to have roofs suitable for solar panels and technologies such as heat pumps work best in well insulated homes like yours.

Why a period property is so expensive to run

On our day-to-day basis (with some 10,000 people visiting the website per day), we tend to get asked plenty of questions about ways to improve the energy efficiency of pre-1930 properties up and down the country. Properties built in this era tend to have a very specific construction type, which makes them slightly tricky to insulate, particularly in terms of wall insulation and it appears that major conurbations in Britain like Greater London, Birmingham West Midlands, Manchester Metropolitan area, Glasgow, etc are really is full of them!

In the winter, period properties (which were largely built from the late 1850’s to 1929) tend to be very draughty and poor at retaining heat when it is cold outside. As a result, they can be costly to run, requiring a lot of heating to keep them at a comfortable temperature. It can even be worse when the winter season drags its feet and the cold snap continues into March, April and parts of May. The resulting energy usage is estimated to be 15 – 20% higher than in normal years.

So you may have a well-insulated loft space and an efficient boiler, but you are still puzzled as to why the property is so bad at retaining heat. The answer is that uninsulated walls can account for 35% or more of the heat loss and unfortunately period properties, which are common across towns and cities, have solid brick walls that are simply terrible at retaining heat.

You can insulate a solid wall

The myth up to now has been that a solid wall cannot be insulated as a retrofit project, because it does not have a cavity that can be filled. This is simply not true. Whilst cavity walls (seen on houses post 1930) are definitely cheaper and easier to insulate (as cavity wall insulation can simply be pumped into the cavity), there are methods available for these old ‘solid’ walls to help them reach more modern energy saving standards.

How do you insulate a solid wall?

Solid wall insulation can work in two ways:

• You insulate the inside of the property, which is referred to as internal solid wall insulation;
• You insulate the outside walls of the property, using external solid wall insulation.

Internal insulation involves thickening the wall from the inside. The process entails adding insulation to the wall and then re-plastering to achieve a nice even finish. With internal wall insulation you just need to be a bit more aware that by adding insulation, the living area will be significantly reduced.

The precise amount of space you lose will vary depending on the degree of insulation. But be prepared to lose 50mm (2 inches at least) to the walls that face the outside exposed walls. The good news is that you don’t need to insulate party walls (the shared walls between adjacent properties) because in theory they are heating the wall from the other side, so no heat loss occurs across this. Therefore if you live in a mid-terrace property, you only need to worry about insulating the front and the back walls of the property.

A more widely used method of insulating solid walls is applying external wall insulation, which is essentially thickening the walls from the outside, then sealing the system with a range of render or brick slip finishes. When you are applying the render products, the finished walls may look different to their original appearance (unless they are already rendered). The render is textured and can be coloured with any colour depending on what you want. The property can also have brick slips installed on top of the insulation to allow the property not to deviate too much from a traditional brick look. However, brick slip systems tend to be quite expensive, which makes rendered finishes more popular and widely used up and down the country.  The video below is an simplified demonstration on how the external wall insulation process works. It does not necessarily capture all the little details, but you will see the key layers that are applied externally to a wall. For more technical information please refer to an appropriate BBA certificate of an external wall manufacturer.

Solid wall insulation and aesthetics

Some of our readers tell us that they love the principle of external wall insulation, but they hate the reality of having to sacrifice property features to do so. Instead of going for the expensive brick slips, the property improver can potentially combine internal insulation at the front elevation (thereby preserving features at street level) with external insulation on the sides and back.

Working around these challenges for a period property will also get you through potential local authority planning hurdles – especially if you live in one of the large metropolitan areas. For example, London has a high proportion of listed properties and large areas that are covered by building restrictions. Therefore it is always worthwhile spending some time familiarising yourself with the rules and regulations covering your local area before you proceed on with your project.

What is the cost of solid wall insulation?

If you were to go to an installer today and inquire about getting solid wall insulation installed, you might be quite shocked by the cost. From data we have collected up and down the country, the price for the measure varies between £80 to £125m per m², depending on the property and the final finish. Internal wall insulation costing varies between £70 to £95m².

There are literally dozens of different variations to external wall insulation finishes. These range from the insulating material used (EPS, mineral wool, cork, etc), to the final topcoat, which can be acrylic (cheapest) or silicone based, to different types of brick slips or specialist finishes.

On the whole, looking purely at economic payback through energy bill savings (i.e. recouping the cost of installation will probably take 20 years + based on the energy savings it will provide), external wall insulation will not look sensible as a standalone metric. However, the external wall insulation system provides additional benefits – it improves the visual appearance of an old render properties and helps waterproof and protect the walls from penetrating damp.

Grants and subsidies for solid wall insulation – do they work?

The economics of solid wall insulation as a standalone indicator didn’t really work until the Government introduced the Green Deal. This was an energy efficiency scheme that was phased out in 2015, and will probably not come back in its previous form. Some homeowners benefited from a grant the Green Deal scheme offered, which essentially paid up to 75% of the total cost. The scheme did not achieve its aim of actually delivering a high volume of external wall insulation improvements up and down the country. This was because the rate of subsidy was set too high and was distributed by a very small number of ‘first come first served’ users.

We believe that external wall insulation not only lowers bills, but also adds value to the property and extends its lifespan. Therefore, if there is a future scheme launched in some shape or form, it has to look at beyond the traditional success indicators, and look at qualitative aims in addition to the economic arguments for it to be successful. A national scheme that is led purely by ‘free money’ does not create the right incentives for the consumer, or to the industry trying to deliver it.

Our prediction is that a future scheme will be based on the ‘pay-as-you-save’ or home improvement loan mechanisms, with very small and targeted amounts of carbon-saving grants. This scheme may have some Government involvement (from a regulation standpoint), but will be very much private-sector led. Expected launch in 2017-18.

Why is the government now not subsidising the cost of solid wall insulation?

The obvious point as to why the Government is not throwing any money at solid wall insulation is that it doesn’t have any money; and secondly, the cost of the measure is quite expensive, therefore requiring quite an outlay to make sure enough consumers out there can benefit from it. Therefore it is too difficult to go back down that road.

The Government is also trying to move away from sponsoring ‘flagship policies’ (Green Deal, Big Society, etc) and pushing more emphasis back on the industry or non-Government sectors to do what it has always done well, which is to deliver for its customers or members. The Government does have to meet carbon reduction targets, but the popular view is that some of those will be missed by 2020, with little worry about the political fall-out from doing so.

Cavity wall insulation and loft insulation are much cheaper energy efficiency measures to deliver to properties in the UK, and the limited ECO funding that is available is going towards some of those measures rather than solid wall insulation.

We are seeing only the most committed home owners or businesses go through the necessary steps to have solid wall insulation implemented on their properties. Very often it is this grouping that really understands the benefits of solid wall insulation and some of its long-term aims, that chooses to make the investment.

To find out more information about solid wall insulation, please see our solid wall insulation section or if you have specific questions, please send us an email to: mailbox@thegreenage.co.uk