How to check energy saving home work won’t cause problems

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Retrofitting the UK’s ageing housing stock to cut carbon emissions is being touted as a way to slow down climate change by government advisors and activists alike.

But while making properties greener is a worthwhile endeavour, the Climate Change Committee and the road-blocking activists of Insulate Britain often fail to mention the costs, disruption and damage this might cause for some British homeowners.

Experts are warning that there are a whole host of ‘risks and compromises’ that can arise when carrying out renovations to improve the energy efficiency of homes. 

Cavity wall insulation can cause serious damp; loft and internal wall insulation could mean sacrificing living space; and installing a new heating system runs the risk of uncovering hidden horrors such as asbestos.

Angela Kerr, director of the HomeOwners Alliance says: ‘Retrofitting for energy efficiency nearly always comes with risks and compromises.

‘You, and the professionals you hire to install eco measures, are unlikely to know everything there is to know about your property, and the materials and building techniques used at the time it was constructed and this introduces an element of risk.’

The government’s current aim is to have as many homes as possible reach an EPC rating of C by 2035 in England and Wales, with an even earlier target being set for privately rented homes.

EPC is a rating scheme which bands properties between A and G, with an A rating being the most efficient and G the least efficient.

At present, about three in five UK homes have an energy efficiency rating of D or worse, according to ONS figures.

Mortgage lenders are also being put under government pressure to improve the overall energy efficiency profile of their mortgage book. 

This has led to a large number of lenders launching mortgages giving special perks to those with homes that are more energy efficient, usually requiring an EPC rating of A or B.

Upgrading homes in England and Wales to meet the targets could cost up to £65billion, according to Government estimates – and at present, homeowners are largely expected to foot the bill. 

This is Money takes a look at the most common retrofitting measures homeowners rely on to improve their EPC rating, and what the potential costs and implications are.

Cavity wall insulation 

Around a third of a home’s heat is lost through the walls, according to the Energy Saving Trust. 

Cavity wall insulation can in some cases help remedy this.

Houses built after the 1920s are more likely to have cavity walls, whilst those built before then are more likely to have solid walls.

A cavity wall is made up of two walls with a gap in between, known as the cavity. T the outer wall is usually made of brick, and the inner wall of brick or concrete.

Most cavity walls can be insulated by injecting insulation material into the cavity from the outside.

A specialist company will drill holes in the outside walls, inject insulation through the holes and then seal them with cement.

What is the cost?

The cost of cavity wall insulation will vary depending on the size of the property, the accessibility of the walls, the type of insulation material and the tradesperson used. 

As a general rule, you can expect to pay around £22 to £26 per square metre, according to Checkatrade.

This means that insulating a typical detached home might cost £725, although those in a mid-terrace property, could expect to pay closer to half that figure.

A Checkatrade spokesperson says: ‘Looking at improving insulation on your home is a good investment when it comes to trying to reduce your energy bills.

‘In the UK cavity walls are most common in houses that were built post-1920 and these are generally quick and easy to insulate.’

What are the downsides? 

In some cases, cavity wall insulation can cause issues such as damp and mould.  

Guarantees exist to protect homeowners against damage resulting from failures in workmanship or materials when it comes to cavity wall insulation.

In the year 2020/21, the Cavity Insulation Guarantee Agency (CIGA) received 2,916 claims, of which almost 1,600 were related to water penetration and close to 600 were related to condensation and mould.

However, claims against cavity wall insulation guarantees are relatively low, according to CIGA, and often problems will arise when an appropriate installer wasn’t used or when a suitable guarantee wasn’t in place.

James Perris, surveyor at De Villiers, says: ‘Cavity wall insulation does unfortunately have problems in some instances.

‘If any gaps are left then you are at risk of “cold bridging” which will manifest itself in mold in your internal rooms.

‘The cavity was designed to prevent penetrative damp so if the insulation has bridged the damp proof course cavity walls, or allows wind driven rain through the wall to the inside then damp patches will begin to appear.’

Internal wall insulation  

Internal wall insulation is one of the most cost-effective methods of insulating the solid walls of older housing stock, though it is more expensive than cavity wall insulation. 

Internal wall insulation is done by fitting insulation boards to the walls inside your home, or by building a stud wall filled in with insulation material. 

It’s typically cheaper and less unsightly than insulating the walls from the outside, however, it will mean compromising on floor space.

According to the Energy Saving Trust, it will reduce the floor area of any rooms in which it is applied as the thickness of the insulation is around 10 centimeters.

What is the cost?

This will vary depending on the number of rooms being renovated and the type of material being used.

Based on a typical three-bedroom semi-detached home, the Energy Saving Trust estimates that it will cost around £8,200. 

The average household could expect to save £210 a year on energy bills thanks to wall insulation.

What are the downsides?

Aside from the cost and the loss of floor space, it’s easy to forget that fittings such as radiators, skirting boards and plug sockets will need to be removed and reattached afterwards.

It may also require re-wiring and re-piping, as well as re-painting and re-decoration after the insulation work has been completed.

If you find yourself having to hire a plumber, electrician and painter, the costs will mount further. 

‘The most off-putting thing for most homeowners is when they hear that it will reduce the floor area of the room,’ says Angela Kerr of the HomeOwners Alliance.

‘But internal wall insulation is also very disruptive. Everything is emptied from the room, even skirting boards and door frames removed.

‘As the walls are lined with insulation and topped with plasterboard, you’ll then struggle to hang pictures and shelves, which is just another frustration.

‘You may also need to completely reconfigure the room. These are the sorts of compromises that, when you add in the costs and hassle involved, it’s no surprise many homeowners procrastinate.’

Like cavity wall insulation, it also brings with it the risk of damp.  

Adding insulation to the inside of a wall will make the original solid wall colder and the difference in temperature between the surfaces inside and outside can cause moisture to form.

This is largely because any water vapour entering the wall from inside will get a lot colder, and may condense inside the wall resulting in damp.

External wall insulation

What is it?

External wall insulation involves fixing a layer of insulation material to the wall from the outside, then covering it with a special type of plasterwork or cladding.

The finish can be smooth, textured, painted, tiled, panelled, pebble-dashed, or finished with brick slips.

It is a less disruptive method, however unlike insulating internal walls, external wall insulation can be more complex and costly.

What is the cost?

Costs can fluctuate depending on whether the home has solid walls or not, as well as if it requires scaffolding.

The cost of external wall insulation is usually around £100 per sq m, with the average cost ranging from £8,000 for a small flat to £22,000 for a large detached house, according to Checkatrade.

What are the downsides?

Similar to internal wall insulation, properties with solid walls need to be able to breathe otherwise damp issues can arise. 

Older properties can also come with unique period features, both outside and inside, which may either have to be lost or prove costly to retain.

A Checkatrade Spokesperson adds: ‘When calculating the cost of insulating the exterior of your home, the area of your walls is a key factor, for determining cost.

‘Beyond this, you’ll need to factor in the cost of adjusting fixtures and fittings that sit on the wall, such as drain pipes and boiler flues.

‘External solid wall insulation should only be fitted by a trained installer.’

Floor insulation

A well-insulated floor can help cut down on draughts at ground level and reduce energy bills. 

Solid concrete flooring became the norm from the late 1930s onwards, and such floors will require insulation laid on top before applying a new floor covering.

Older homes are more likely to have suspended timber floors, which can typically be distinguished by air vents on the outside walls located below floor level.

Timber floors can be insulated by lifting the floorboards and laying mineral wool insulation, supported by netting between the joists.

What is the cost?

The average under floor insulation starts at £770 for a smaller room and up to £1,000 for larger rooms.

However, it can be easy to forget that there can be associated costs on top of this such as re-flooring or re-carpeting.

Those looking to insulate over the top of solid concrete floors should expect to pay between £950 and £2,200 per room, according to Checkatrade.

When insulating under a suspended timber floor you can expect to pay much less – typically between £300 and £750 per room.

What are the downsides?  

Other than the disruption of moving furniture and the potential re-flooring required, room insulation is one of the least disruptive eco improvements one can make.

Those with suspended timber floors, will likely need to lift the floorboards to insulate underneath and this may require re-filling between the gaps afterwards.

Homeowners must also avoid blocking up the air vents underneath as this could lead to damp and even the floorboards rotting.

Loft insulation

Insulating your loft is good for energy efficiency, heat retention, and keeping the cost of bills down.

A quarter of heat is lost through the roof in an uninsulated home, according to the Energy Saving Trust.

It can therefore be one of the simplest and most cost-effective ways to make your home more energy efficient.

It is typically achieved by using rolls of mineral wool insulation with the first layer laid between the joists and further layer to cover the joists.

What is the cost?

For those looking for a good return on their eco investment, adding loft insulation could be a no-brainer.

The average cost of labour and materials is £500, according to Checkatrade, ranging from £400 for a mid-terraced house to £600 for a detached house or bungalow.

The potential saving on energy bills may make it even more appealing. 

Those in a detached home could expect to save £380 a year on average according to the Energy Saving Trust, while a mid-terrace house will typically save £150 a year. 

‘I would almost always start at the top – literally – with loft insulation – it’s reasonably priced, effective and involves least disruption to your home,’ says Kerr.

What are the downsides?

As with wall insulation there is a risk of damp.

Preventing hot air from escaping your home will make your loft cooler which could exacerbate damp and condensation issues.

Loft insulation can either be laid across the floor of the loft, or in the rafters – or both.

Like internal wall insulation, it might also make your loft seem smaller which could be a problem if it is a room you wish to use. It typically requires between 12cm and 30cm of insulation.

‘The downside to retrofitting loft insulation is that it’s more involved than you might think,’ adds Kerr.

‘You need to lay it across and over and not just between the rafters to ensure you have enough.

‘But you can’t then squash it with boards. Instead you need to create a new floor. That’s beyond a lot of homeowners’ DIY skills, so experts may need to be called in, adding to the costs.

‘Homeowners should also be aware that a new, higher floor will mean a loss of headroom and manoeuverability in the loft, which are often quite tight spaces to start with.’

Double glazing

Double glazed windows are another effective eco-friendly home improvement that will boost your home’s energy efficiency.

Upgrading from single glazing to double glazing also comes with the twin advantage of cutting your energy costs and also reducing noise from outside – which can be particularly important if you live along a busy road.

Kerr says: ​​’There are definite advantages to getting double glazing – it’s surprisingly not very disruptive and we know that it’s very popular.

‘Everyone wants double glazing so it is an advantage if you are going to sell your home and it’s also a great way to reduce noise from a noisy street or neighbors.

‘A good window fitter will come and take measurements and return to fit it, without causing any disruption to the decoration to the inside or outside.’

What is the cost?

What you will end up paying will depend largely on the type of windows you have. 

Replacing PVC windows will be cheap in comparison to sash windows for example.

PVC windows tend to be cheapest, with a set of windows for a typical semi-detached house costing around £4,250, compared to around £15,000 for hardwood windows, according to the Energy Saving Trust.

As returns on investments go, it isn’t great either. A typical home could expect to cut their energy bill by only £95 a year by upgrading from single to double glazed windows.

What are the downsides?

A key issue with double glazing is that for all the benefits it brings, it can look slightly out of place in some cases – particularly when dealing with sash windows and older properties.

‘Sash windows are an important and valuable feature of many period homes, but are usually quite draughty,’ says Kerr.

‘Most window suppliers will do a double glazed and well-sealed version of sash windows and these can come in wood or uPVC to reduce costs, although they are still very expensive to replace.

‘Despite energy savings to be had, the charm of original windows means it’s understandable why homeowners aren’t rushing out to replace them at great expense. Most will look at secondary glazing and repairs to existing frames first.’

Heat pumps

If you’re prepared to upgrade to an eco-friendly renewable heating system, you have a number of options including air source heat pumps and ground source heat pumps.

A heat pump captures heat from outside and moves it into your home. 

Although it uses electricity to do this, the amount of heat delivered into your home should be much greater than the amount of electricity used to power the system.

As a heat pump captures heat that is already present in the environment, the system itself does not burn any fuel and therefore emits no carbon dioxide.

What is the cost? 

On average, the supply and installation of an air source heat pump will cost between £3,000 and £18,000, according to Checkatrade.

An average ground source heat pump installation for a typical house will cost between £13,000 and £35,000, according to Checkatrade.

Only one in five homeowners want to install a heat pump, according to research by Evergreen Energy. 

What are the downsides?

Aside from the high upfront cost, the installation will likely cause a significant disruption to your home and garden.

There are also reports that they are not as effective at heating your home as traditional gas or oil powered boilers.

Heat pumps are known to be less efficient in winter. This means they often need to run constantly during the winter months which can eat into any savings. 

You will therefore need to have a highly insulated home to reap the full benefits.

What else should homeowners look out for?

When renovating your home you can unearth issues that may have been best left alone – none less so than asbestos.

Asbestos was widely used in building materials from around 1930 through to the mid-1980s, but according to the Health and Safety Executive, it could be found in any building built or refurbished before the year 2000.

The British Lung Foundation estimates that some 14million UK homes were built when asbestos was being used in the construction industry.

Materials that contain asbestos pose very little risk when left alone, but if they are disturbed or damaged they can be very dangerous.

Fibres are released into the air which if inhaled can lead to serious health conditions including mesothelioma, lung cancer and asbestosis in later life.

Before the health implications of asbestos were known, products containing it were used for all manner of things – as a fire retardant, to lag pipes, in wall and roof insulation, or sprayed on to ceilings and walls as a decorative coating.

Mark Button, managing director at asbestos management firm ARL Asbestos says: ‘Externally asbestos was commonly used in roofing slates, soffits and fascias as well as roofing felt, gutters and downpipes, all which can be impacted on is fitting solar panels and replacement soffits, fascias and high efficiency flat roofing products.

‘Internally, adding loft insulation can mean disturbing asbestos water tanks, asbestos flues from boilers and even asbestos insulation to older pipework.

‘In the living areas of the property, textured ceiling and wall coatings commonly contained asbestos as did floor tiles, vinyl flooring and associated flooring adhesive.

‘Upgrading to an energy efficient boiler can lead to accidental disturbance of asbestos used for fire proofing to the boiler cupboard and pipe runs. Even old toilet cisterns can contain asbestos.’

‘For those needing to rewire, it’s worth knowing that asbestos was common in fuse boards and electrical components.’

Even those thinking about replacing windows for double glazing might not be safe.

‘Any works in a building could potentially unearth asbestos – even changing windows as asbestos was even used to pack out window frames,’ says Perris.

‘Furthermore, if the contractor is drilling into panelled walls then they should get the boards tested before proceeding.’

With that in mind, those living in older properties might be wise to arrange an asbestos survey before starting energy-saving renovations.

‘It is a legal requirement that contractors carrying out this work should identify the hazard in advance and risk assess it and not expose the homeowners to any risk,’ adds Button.

‘Whilst this is the law, it is ignored very often, either through ignorance or choice. We have had to pick up the pieces many times after a cowboy contractor has been engaged.’