Home Insulation: Save Energy, Cut Costs & Stay Cosy

If your home often feels colder than it should, or your heating seems to be working overtime, you’re not alone. Your home could be losing more heat than you realise, and that wasted warmth is money drifting straight out of the door, roof or walls.

Learning how to insulate your home is one of the best ways to improve home energy efficiency, lower your carbon footprint and stay comfortable all year round. Better home insulation keeps you warmer in the winter, cooler in summer and prepares your home for low-carbon heating systems like heat pumps.

And the good news? You don’t need a full renovation to make a real difference. Even small changes to home insulation can reduce heat loss and cut down your energy bills.

Many UK homes, especially older ones, still have thin or outdated insulation. Materials settle, slump and degrade over time too, which means a significant number of homes are under-insulated and need to improve their energy efficiency.

With colder weather already here and government grants available for some households, there’s never been a smarter time to learn how to insulate your home.

How Homes Lose Heat & Why Insulation Helps

Poor insulation in homes means you lose heat much faster, so your boiler or heater has to work harder just to keep the temperature comfortable. According to Energy Saving Trust, a typical uninsulated home loses roughly:

25% through the roof
33% through the walls
10-20% through the floor

This lost heat is a form of “unwanted energy transfer” – heat escaping into the air around your home where it’s very difficult to recover, instead of staying inside where it’s useful.

Insulation in homes slows this transfer, helping your home stay warmer for longer and cutting down on wasted energy. While no home can stop heat loss entirely, the right home insulation can significantly reduce it.

Types of Home Insulation

Loft, Roof & Attic Insulation

Loft insulation is usually the simplest, most cost-effective way to reduce heat loss in a house. Correctly installed, loft insulation can last around 40 years, paying for itself multiple times over.

Common home insulation materials include fibreglass, mineral wool, foam boards and natural fibres such as cork or wood, and the recommended insulation depth is 270mm.

Things to consider:

Insulated loft hatches and added draught excluder strips around the frame edges can prevent cold air from dropping into the rooms below.
If you use your loft for storage, don’t worry – you can still add insulation. Simply raise the floor slightly, add the layer of insulation across the top of the joists, then fit boards on the loft floor, so you get the benefits of insulation without losing valuable storage space. Be sure to leave a small gap for ventilation and if you’re using mineral wool, make sure not to squash it, as this will reduce effectiveness.
Without good ventilation, warm air from your home can get trapped in the loft. Condensation can cause damp, mould, or even rot in the roof’s timber. If you’re doing any DIY insulation, make sure you don’t squash the insulation material, and keep any vents, grilles or airbricks clear. It’s a good idea to get professional advice if you’re unsure about how home insulation will change the ventilation in your loft.
Be sure to fix any damp or structural issues before adding insulation. This isn’t a suitable task for DIYers, so speak to a professional installer.
Insulating flat roofs, rafters, loft conversions used as living spaces or any rooms with sloping ceilings is also a job for professionals.
Hard-to-reach lofts can be insulated by a professional with blown insulation materials like loose mineral wool fibre, treated cellulose or polyurethane foam.

Cavity Wall Insulation

Most homes built after the 1920s have cavity walls – two layers of masonry with a gap in between. Filling this cavity with home insulation helps to trap heat and reduce draughts and condensation. In general, houses built after 1990 will already have wall insulation as standard, but if the house is older than that, it might not.

Cavity wall insulation may not be suitable for you if:

your home is exposed to driving rain or flooding
your walls are in poor condition
the cavity is too narrow, less than 50mm (common in pre-1920s builds)
your property is prone to overheating

If you’re unsure what type of walls you have then it’s best to ask a specialist installer or other building professional.

Solid Wall Insulation

Older homes (pre-1920s) often have solid walls with no cavity, which lose heat more quickly. Solid walls can be insulated on the outside surface of the wall (external wall insulation) or on the inside surface (internal wall insulation).

Solid wall insulation is highly effective – especially for homes with single brick, timber frame or thin stone walls – but it’s also one of the more expensive upgrades.

Things to consider:

Solid wall insulation might not be suitable if your home is exposed to extreme weather, flooding or is in a poor condition, or if rooms are at risk of overheating. Check for these risks with an experienced installer or professional.
External insulation can cost less when combined with other outdoor improvements like roofing, repairing gutters or installing new windows or solar panels.
Internal insulation requires redecorating and may reduce room size slightly.
Damp or structural repairs (dealing with damaged brickwork or pointing, repairing roofs and overhangs, or renewing gutters and downpipes etc) must be completed before installation to avoid trapping moisture.

Floor & Basement Insulation

Floor insulation can cut draughts and make rooms feel noticeably warmer underfoot. You usually only need to insulate ground floors, but if a room sits over an unheated space like a basement or garage, it can benefit too.

Older homes often have solid floors made of flagstones, tiles laid over earth or lime-based material, with no insulation at all. Insulation can be complex in these properties, so it’s best to consult a professional.

In Victorian and Edwardian homes with suspended timber floors, heat escapes into the empty space beneath. Insulation is typically fitted by lifting the floorboards and laying mineral wool insulation or rigid foam boards between the floor joists.

Many homes built from the 1950s onwards have solid concrete floors, and those built from the early 2000s likely included insulation as part of the construction. If not, laying rigid insulation boards over the top will add a layer between your home and the cold ground.

Because floor types vary, it’s often worth getting professional advice before you start lifting boards or altering original floors in older properties.

Pipe, Tank & Radiator Insulation

These are some of the easiest and most low-cost ways to reduce heat loss in a house.

Water tanks can be insulated with a hot water cylinder jacket. It should be at least 80mm thick. By adding an 80mm British Standard insulating jacket to a tank with 25mm of foam built-in, you will spend less money heating water up, and hot water will stay hotter for longer.
Pipe insulation helps to stop downpipes, wastewater and sewage pipes from freezing, cracking or bursting in cold weather. It reduces heat loss from hot water pipes, especially in unheated spaces like lofts, basements and garages. Cheap and readily available in DIY shops, polyethylene foam or rubber tubes (that you can cut to size) can be wrapped around pipes and sealed with insulated foil tape.
Radiator reflector panels fitted behind radiators on external walls will bounce heat back into the room instead of letting it escape through the wall.

Always remember to turn off heating and hot water before touching pipes and make sure you can reach tanks safely using secure boards in the loft.

Draught Proofing & Sealing

Good ventilation is essential for a healthy home, but uncontrolled draughts are simply wasted heat.

Common draught spots include:

gaps around doors, windows and stairways
cracks in floorboards, skirting boards and beams
gaps around pipes and cables passing outside
loft hatches and fireplaces

Listen for rattles and whistling noises, feel for air moving around, look for curtains moving and visible light under and around doors and windows.

Simple DIY fixes like draught excluders and self-adhesive foam strips can make a big difference. Just avoid blocking any window or wall vents, as this could lead to damp or mould problems.

Older properties can be a little trickier to draught-proof on your own. A professional installer can make sure open flues, chimneys and moisture-heavy rooms stay safely ventilated.

Important Safety Note

Homes with gas appliances, open fires or open flues require particular care. These rely on a constant supply of ventilation to operate safely.

If ventilation is reduced or blocked during draught proofing, and a room becomes oversealed, it can increase the risk of gases such as carbon monoxide building up inside the home – instead of being safely vented outside.

Carbon monoxide is a colourless, odourless gas and is extremely dangerous. Even minor cases of carbon monoxide poisoning can lead to serious brain, heart and organ damage, potentially resulting in death.

You can learn more about the symptoms and risks of Carbon Monoxide poisoning here.

Older properties can be especially tricky to draught-proof safely, but a qualified professional can ensure:

open flues and chimneys remain properly ventilated
moisture-heavy rooms like kitchens and bathrooms still extract air effectively
energy efficiency improvements do not compromise indoor air quality or your safety

Calculating Cost, Savings & Payback

The cost of home insulation varies depending on the type, size of the home and how under-insulated it is now. However, the principle is the same: the better your home insulation, the less heat escapes – and the more home energy savings you can enjoy.

Typical Costs & Savings

Loft / roof insulation

Installation cost: it costs £900 to insulate a depth of 270mm from 0mm, and £750 to insulate a depth of 270mm from 120mm, for an average semi-detached home.
Home energy savings: insulating from 0mm to 270mm could save an average semi-detached house around £230 each year, a detached house £390, a mid-terrace house £210, and a detached bungalow £380. Insulating from 120mm to 270mm could save a detached house or bungalow £35 on their energy bills each year, and a semi-detached and mid-terraced house £20.

Cavity wall insulation

Installation cost: around £2,700 for an average semi-detached home.
Home energy savings: around £240 each year for an average semi-detached house, £140 for a mid-terrace house, £180 for a detached bungalow, £120 for a mid-floor flat and £420 per year for a detached house.

Solid wall insulation

Installation cost: external wall insulation costs around £18,000, and internal wall insulation, around £12,000. Or potentially less if you’re having it done at the same time as other work.
Home energy savings: around £330 each year for an average semi-detached house, £200 for a mid-terrace house, £250 for a detached bungalow, £160 for a mid-floor flat and even £550 per year for a detached house.

Floor / basement insulation

Installation cost: between £1,400 and £2,500, depending on your house type.
Home energy savings: around £70 each year for a semi-detached house, £120 per year for a detached house, £45 for a mid-terrace house, and £120 for a detached bungalow.

Insulating tank & pipes

Installation cost: a hot water cylinder jacket costs around £18, and primary pipe insulation should also cost around £18.
Home energy savings: adding an 80mm British Standard jacket to a tank with 25mm foam built-in can save £40 to £50 per year on your energy bills.

Draught proofing

Installation cost: DIY materials are cheap and widely available. Professional draught proofing of windows and doors could cost around £250 for your whole house.
Home energy savings: draught proofing around windows, floors and doors could save you an average of £85 per year on your heating bills.

Grants, Schemes & Support

If the upfront costs of home insulation feel overwhelming, you’re not alone. It’s worth checking whether your household can get help to reduce those costs, or even cover them completely:

Energy Company Obligation (ECO4): supports low-income and vulnerable households with insulation upgrades until 31^st March 2026, improving home energy efficiency. You may qualify if you receive certain benefits and are a homeowner or private tenant, with an energy performance rating (EPC) of D to G.
Great British Insulation Scheme (GBIS): offers help for homes with lower EPC ratings, those in certain council tax bands, or households receiving certain benefits, to tackle fuel poverty and help reduce energy bills. Installations must be completed by 31^st March 2026, and although the service to check if you’re eligible has closed, some energy suppliers are still accepting applications. It’s best to check with your supplier.
The Warm Homes: Local Grant: designed for improving home energy efficiency and increasing low carbon heating installations for low-income households. The scheme has been allocated £500 million for 73 projects across 270 local authorities, to be delivered from April 2025 to March 2028.
Boiler Upgrade Scheme: you could get a grant to cover part of the cost of replacing fossil fuel heating systems including oil, gas, electric or LPG (liquefied petroleum gas) with a heat pump or biomass boiler.

Find out more about getting help with your energy bills here.

How to Insulate Your Home Effectively

Where to Start

If you’re planning how to make your home more energy efficient in stages, tackle the biggest heat-loss areas first:

Loft/roof insulation: the quickest win for most homes.
Walls: if you’re not sure whether you have cavity or solid walls, contact a professional.
Floors: especially suspended timber floors or rooms over unheated spaces.
Pipes, tanks and draught proofing: low-cost additions that can be carried out throughout steps 1-3 to boost overall efficiency.

DIY vs Professional Installation

Ideal DIY jobs: draught proofing, pipe lagging, hot water cylinder jackets and simple loft insulation top-ups.
Best left to professionals: solid and cavity wall insulation, rafter insulation, insulating flat or sloping roofs and loft conversions, complex floor insulation (you might be comfortable insulating a timber floor, but it’s more complicated than it looks!)

Choosing the Right Materials

Home insulation comes in rolls, boards or spray forms.

Key things to check:

Thickness: 270-300mm in lofts. For floors, depends on structure, for walls 100-150mm.
Material: mineral wool, rigid boards, spray foam, fibreglass or natural fibres all perform differently.
Thermal performance: look for good thermal performance (measured as U-values or R-values). The R-value demonstrates the material’s thermal performance, or resistance to heat flow. U-value is the performance of the heat transfer through an element of the building such as a wall, roof or window. The R-value is a factor of the U-value – so, the R-value of a material used in the wall insulation will affect the U-value. Higher R-values and lower U-values indicate better thermal performance

Again, if you’re unsure how to make your home more energy efficient, it’s best to ask an installer for advice.

Avoiding Common Pitfalls

Moisture issues: always fix leaks and address condensation and damp problems before carrying out any home insulation.
Insulation damage: gaps, squashed insulation, or damage from pests can create gaps and voids in insulation where heat escapes. This can mean higher costs to heat your home.
Blocked ventilation: good airflow will prevent mould, so never cover vents, flues or airbricks.

Maintaining & Upgrading Over Time

Home insulation lasts a long time, but not forever. It can settle, degrade or become damaged, reducing its performance over the years.

A quick annual check can tell you a lot about how your home insulation is doing. Look for:

Depth: is your loft insulation still at least 200mm deep?
Coverage: is there a continuous layer, or can you see gaps where air could pass?
Condition: are there areas that are sagging, flattened or disturbed?
Moisture: are there any signs of damp, mould or wet patches?
Airflow: are there any draughts? Have any vents been accidentally covered?
Energy bills: have your heating costs crept up without a clear reason?
R-value & EPC rating: check the insulation material label or contact a professional to find out your R-value. Check your EPC rating too, as one of the main causes of poor EPC performance could be the state of your insulation.

If you’re unsure about the state of your home insulation, contacting a professional is the safest option.

Damage to Look For (and What It Means)

Different types of damage affect home insulation in different ways:

Water or damp: wet insulation stops working properly and can encourage mould. It always needs replacing to avoid health risks and structural problems.
Fire or heat damage: insulation exposed to fire or high heat can lose effectiveness and may release harmful substances. It must be replaced.
Compression and sagging: insulation that’s been flattened under storage boards or simply slumped over time down to 100mm can lose up to 50% of its performance (UK’s National Physical Laboratory).
Crumbling or degraded material: older insulation can break down and won’t provide proper coverage. It needs removing and replacing.
Heavy dust build-up: dust building up reduces airflow and insulation performance. It can mean the material has reached the end of its life.

Pests: What to Check and How to Spot a Problem

Mice, rats and other pests sometimes settle in lofts and crawl spaces because they’re warm, quiet places to nest. Unfortunately, they can cause significant damage to your home.

Why pests matter:

They shred insulation to make nests.
Their droppings, urine and skin can contaminate insulation and lower indoor air quality, causing respiratory issues for your family.
Their waste can attract more pests, making the issue worse over time.

Signs of pest damage include:

Shredded, gnawed or disturbed insulation material
Droppings or a strong musty odour
Discolouration and stains
Sagging or compressed areas
Scratching or scurrying noises (often at night)
Gnawed cables, pipes or timbers near insulation

Any pest-contaminated home insulation must be removed and replaced. Always deal with the infestation first so the new insulation isn’t damaged again, and to avoid health risks.

Topping Up Loft Insulation

If your insulation is thin, patchy or has been disturbed, topping it up is one of the easiest and most cost-effective improvements to keep an energy-efficient home.

Before topping up:

Make sure the existing insulation is dry and in good condition before adding any more on top.
Wear protective gloves, long sleeves and a face mask to protect yourself from fibres and dust.
Use the right material for your home and roof type.
Keep any vents clear so moisture can escape.

A professional can help if you’re unsure about the type of home insulation you need, or if your loft is difficult to access.

Monitoring Performance

Even without looking in the loft, you can spot when home insulation isn’t working as well as it used to:

Rooms feel colder or draughtier than normal
The heating takes longer to warm up the house
You need to keep the heating on for longer
Your energy bills increase unexpectedly
You spot areas of damp where previously there were none

Small issues caught early can prevent heat loss and help maintain an energy-efficient home that’s warm, dry and keeps energy costs to a minimum.