Reduce Gas Bills by Insulating Your Home

By insulating our homes, we reduce the demand for energy and burn less fuel, which helps combat climate change and protects the planet.

Insulating the loft, walls and floor of your home is a great way to reduce energy bills every year from a one-off activity. The average UK energy bill is over £1,200 per year. Heating and hot water account for around 80% of our home energy consumption.

Around 50% of heat in a house escapes through the roof, walls, windows and floors if a building is not insulated. Insulation is the equivalent of putting a big warm blanket around your house and it doesn’t have to be expensive or difficult.  

A staggering 16 million UK homes don’t have the standard 27cm of loft insulation and because insulation is ‘invisible’ in walls or under the floor it’s doesn’t always spring to mind when considering energy efficiency measures.

There are lots of low-cost energy conservation measures to fix the problem of heat loss through walls or floors, many of them are quick, easy solutions. Energy efficiency – particularly through insulation - is a way of saving energy at home and improving your comfort whilst cutting your energy bills. Quite simply, you can fit and forget them. A guide to costs, savings and carbon dioxide emissions avoided for a typical home is provided at the bottom of the page for each measure.

Roof Insulation

Insulating your loft to a standard depth of 27cm, which is almost the length of a school ruler. This is probably the easiest and most effective way to keep heat in your home and stop it escaping into thin air! Rolling out mineral wool or another product in your loft, will last for around 40 years and have a pay back of about 6 years.

Many people choose to fit the insulation material such as mineral wool themselves and this handy video explains how. If you have the rolls fitted by an installer, they may be able to fit some boards over the insulation and near the loft hatch so, you can still store Christmas decorations in the roof. 

How to Lay and Fit Loft Insulation

Here is a two-minute video on How to Lay and Fit Loft Insulation.


Wall Insulation

Modern homes are increasingly efficient and air tight. If your home was built after 1990, the good news is it will have had insulation added during construction.

However, this is not true for the majority of houses in the UK. Over 5 million homes have uninsulated cavity walls and only 8% of the 8.5 million homes with solid walls have been insulated; there is huge potential to reduce heating bills for families living in these homes.

Cavity Wall Insulation

If your home was built between 1930 and 1990 it is likely the construction method used was two brick walls built with a gap in between. This cavity wall structure originally had no insulation.

Filling a cavity wall is quick and easy and there may be a Government grant available.  Installers take about two hours to fill the cavity before they seal up the tiny holes they drilled. They use polystyrene beads that don’t absorb water so there are no damp problems. The insulation retains heat in your home and stop it escaping outside. Therefore, your home will be warm but there will be no change in the appearance of your house and pretty much no hassle.  Just cheaper bills and less gas burnt so lower carbon dioxide emissions. A real win win!

It’s easy to check if your house already has wall insulation, you can look around the brick work for signs of circular holes where someone has drilled into the cavity or ask an installer to visit.

Is the Structure of My House Safe with Cavity Wall Insulation?

If you are not sure if your home is suitable for cavity wall insulation, ask a registered installer to come and review your property. Before going ahead with cavity wall insulation, get three written quotes from companies approved by the Cavity Insulation Guarantee Agency.

Previously, expanding foam was used for cavity walls but as technology progresses most installers use polystyrene beads. The national cavity wall insulation guarantee provides a 25-year independent assurance on the work on your home when using a registered installer.     

Options for Solid Wall Insulation

Insulation board being fitted in a homeNearly half of all heat produced in a home escapes through solid walls. Older homes (pre-1920) are likely to be built using a single solid wall of bricks or stone. If your brickwork is a mixture of long and short bricks then it is likely of solid wall construction.

It is still possible to insulate these walls by adding a layer of insulating material either on the inside or the outside of the house. The choice is very much up to your individual preference and budget.

It may be worth getting the opinion of an RICS surveyor before deciding to invest in solid wall insulation. The cost of a surveyor’s report is not high in comparison with the cost of external or internal insulation and is independent and covered by professional indemnity insurance.

Internal Insulation

Internal insulation entails adding insulation boards or lining to the solid walls, resulting is a slight loss of internal space in each room. Internal insulation is cheaper than external insulation, around £6,000 depending on the size of the property. There may be grants available through Government schemes. Your installer will be able to advise on this.

External Insulation

External insulation adds an extra thermal layer onto the outside wall, which is then finished off with a protective render or cladding. This process is less disruptive and retains the original room sizes. However, it is more expensive due to the materials required and will change the look of your property. If your home is in a listed or conservation area, external solid wall insulation may not be suitable.

The cost will very much depend on the size of the property, but a typical home is around £10,000 (grants may be available through Government schemes) again, your installer will be able to offer advice.

Floor Insulation 

Cat sitting on carpetIf you were planning to lay new flooring or have a particular problem with drafts from ground level, floor insulation is a good idea.

Draughty gaps between floor boards or skirting boards can easily be plugged using filler from DIY stores. For wooden floors, the easiest method is to attach solid insulation boards or rolls of mineral wool between the timber joists from a basement below the room. For many homes this is not possible, as floor boards will need to be lifted. If you use a professional, this could cost around £800, depending on the floor area. It’s much cheaper if you can do it yourself.

Rigid insulation boards can be fitted over concrete floors as well, but doors may need to be adjusted and a damp proof membrane added. 

If all this seems too complex to tackle, then thermal underlay is effective and cheap. You will find a good guide to floor insulation via the Which? website.

Grant Funding for Free Insulation and Boilers

There is a huge need to ensure people are safe and warm in their homes as well as to reduce carbon emissions from heating. There are Government grants available for energy efficiency measures in our homes. The grants are particularly tailored towards those that receive any form of benefits or Government support.  Please do use this financial support as it will save you money and also help save the planet. 

Funding is available under the Energy Company Obligation (ECO2t) scheme to have your home insulated for free, a new boiler or other energy saving measures.  You could qualify for support through the ECO2t scheme for a new boiler, if you are in receipt of any benefits or tax credits.

Further Information and Advice on Insulation and Energy Efficiency Measures

To find out more, Home Energy Scotland is on 0808 808 2282 and if you are in Northern Ireland, you can call Northern Ireland Energy Advice on 0800 1422 865.  They often take down your details and someone with relevant expertise will ring you back depending on your enquiry but they are usually friendly, helpful people.

There are many great websites such as EST and CSE that describe the best way to fit insulation.

Insulation options and their payback for England, Scotland and Wales from the Energy Saving Trust

These savings are for typical gas-heated homes so if a home is heated by oil or lpg then the savings will be higher.

Loft insulation (0 to 270mm) Detached house Semi detached house Mid terrace house Detached bungalow
Fuel bill savings (£/year) £225 £135 £120 £195
Typical installation cost* £395 £300 £285 £375
Carbon dioxide savings (kgCO2/year) 990 kg 590 kg 530 kg 850 kg
Payback 2.5 years or less


Loft insulation top up (120 to 270mm) Detached house Semi detached house Mid terrace house Detached bungalow
Fuel bill savings (£/year) £20 £10 £10 £15
Typical installation cost* £290 £240 £230 £280
Carbon dioxide savings (kgCO2/year) 90 kg 50 kg 50 kg 80 kg
Payback time less than 24 years if contracted or much less if DIY

Estimates based on insulating a gas-heated home with either a totally un-insulated loft, or topping up existing insulation from 120mm to 270mm. (The recommended depth for mineral wool insulation is 270mm but other materials need different depths).

*Average unsubsidised professional installation costs, although these will vary. Find out more about our calculations. Figures are based on fuel prices as of April 2017.

Cavity Wall Insulation Detached Semi detached Mid terrace Bungalow Flat
Fuel bill savings (£/year) £225 £150 £95 £105 £70
Typical installation cost £720 £475 £370 £430 £330
Payback time 5 Years or less
Carbon dioxide savings (kgCO2/year) 1,120 kg 670 kg 410 kg 450 kg 310 kg

These are estimated figures based on insulating a gas-heated home. The average installed cost is unsubsidised. Figures are based on fuel prices as of April 2017.

Wall Insulation Detached Semi detached Mid terrace Bungalow Flat
Fuel bill savings (£/year) £425 £255 £160 £175 £120
Carbon dioxide savings (kgCO2/year) 1,870 kg 1,120 kg 690 kg 760 kg 520 kg
Typical installation costs*

External wall insulation: £8,000 to £22,000

Internal wall insulation: £4,000 to £13,000

Payback time

External Wall Insulation 18 years +

Internal Wall Insulation 9 years +

Estimates based on insulating a gas-heated home. Costs may vary significantly depending on level of work required. Above estimates are based on a typical install, ranging between a small flat and a large detached home. Figures are based on fuel prices as of May 2017. 

Floor Insulation Detached Semi detached Mid terrace Bungalow
Fuel bill savings (£/year) £65 £40 £25 £60
Carbon dioxide savings (kgCO2/year) 290 kg 170 kg 120 kg 260 kg
Typical installation cost From £950 to £2,200
Payback time Between 14 to 88 years

Estimates based on insulating a gas-heated home. Costs may vary significantly depending on level of work required. Figures are based on fuel prices as of April 2017.




This information is provided for guidance only. Please see the full disclaimer in our terms and conditions.


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