Home Insulation Guide UK: Every Type Explained with Costs and Savings#

Insulation is the single most effective way to reduce energy bills in a UK home. A well-insulated house uses less energy to heat, stays warmer for longer, and costs far less to run. Yet millions of UK properties still have little or no insulation in key areas.

This guide covers every major insulation type available to UK homeowners in 2026, from loft rolls you can fit yourself to professional solid wall systems costing thousands. For each type you will find realistic costs, estimated annual savings, and whether grant funding is available.

Why Insulation Should Be Your First Investment#

Before upgrading your boiler, installing a heat pump, or switching tariff, insulation should come first. The logic is straightforward: there is no point generating heat efficiently if it escapes through poorly insulated walls, roofs, and floors.

Insulation works by trapping pockets of air within a material, slowing the transfer of heat from inside your home to the colder outside. The better the insulation, the less energy your heating system needs to maintain a comfortable temperature.

The benefits go beyond lower bills:

• Reduced carbon emissions — a well-insulated home produces fewer greenhouse gases
• Improved comfort — fewer cold spots, draughts, and temperature swings between rooms
• Less condensation and damp — stable internal temperatures reduce the risk of mould
• Higher property value — a better EPC rating makes your home more attractive to buyers

Types of Home Insulation at a Glance#

UK homes lose heat in different ways depending on their age, construction, and condition. The table below summarises every major insulation type, with costs and savings based on Energy Saving Trust figures for a gas-heated semi-detached house.

Loft Insulation#

The loft is the easiest and cheapest place to start. Heat rises, and in an uninsulated home around a quarter of it escapes through the roof. Installing or topping up loft insulation delivers some of the fastest payback of any home improvement.

The recommended depth for mineral wool loft insulation is 270mm. Many older homes have 100mm or less — well below the standard set out in current Building Regulations.

What It Involves#

For an accessible loft with a cold roof (where the insulation sits at ceiling level rather than between the rafters), the process is simple. Mineral wool rolls are laid between the joists, then a second layer is rolled at right angles across the top to eliminate cold bridges and reach the full 270mm depth.

Who Should Get It#

Almost every home with an accessible loft benefits from topping up or installing loft insulation. The only exceptions are homes where the loft has already been converted into a habitable room (which requires insulation between the rafters instead) or where there are serious damp or structural issues that need resolving first.

For a full breakdown of materials, DIY instructions, and grant options, see our dedicated loft insulation guide.

Cavity Wall Insulation#

Cavity wall insulation is the single most impactful measure for the majority of UK homes built after the 1920s. These properties have two layers of brickwork with a gap (cavity) between them. That gap was originally designed to stop damp penetrating the inner wall, but it also acts as a channel for heat loss.

How It Works#

A trained installer drills small holes into the outer wall at regular intervals, then injects insulating material — usually mineral wool fibre, polystyrene beads, or polyurethane foam — into the cavity. The holes are filled and made good afterwards.

The entire process takes around two to three hours for a standard semi-detached house and causes minimal disruption. There is no internal work required and no loss of room space.

Costs and Savings#

Cavity wall insulation typically costs between £400 and £1,500 depending on the size and accessibility of the property. The Energy Saving Trust estimates annual savings of up to £395 for a semi-detached home, making the payback period as short as one to four years.

Is Your Home Suitable?#

Not all cavity walls can be insulated. Homes with very narrow cavities (less than 50mm), severe damp problems, or exposed locations subject to driving rain may not be suitable. A pre-installation survey by a registered installer will determine whether your walls can be treated.

Solid Wall Insulation#

Around a third of UK homes — including most properties built before the 1920s — have solid walls with no cavity. These walls lose heat almost twice as fast as unfilled cavity walls, making solid wall insulation one of the most beneficial upgrades for older properties.

There are two approaches: internal and external.

Internal Wall Insulation#

Rigid insulation boards or a stud wall packed with insulation material are fixed to the inside face of external walls. This is the cheaper option but does reduce room sizes slightly (typically by 60mm to 100mm per wall).

Typical cost: £4,000 to £13,000 for a whole house, depending on the number of rooms and complexity.

Internal insulation works well when:

• The external appearance of the building must not change (listed buildings, conservation areas)
• Only one or two rooms need treating
• Budget is limited compared to external options

External Wall Insulation#

Insulation boards are fixed to the outside of the walls, then covered with a protective render or cladding. This transforms the appearance of the building and eliminates cold bridges more effectively than internal insulation.

Typical cost: £8,000 to £22,000 for a whole house.

External insulation is the better technical solution in most cases because it wraps the entire building envelope without interruption. However, it requires scaffolding, planning permission in some cases, and is significantly more expensive.

Savings#

Both methods deliver similar energy savings — up to £465 per year for a detached house, according to the Energy Saving Trust. For a semi-detached property the figure is around £260 per year.

Floor Insulation#

Around 15 percent of heat loss in an uninsulated home occurs through the ground floor. Floor insulation is often overlooked because it is less visible than loft or wall work, but it makes a noticeable difference to comfort, particularly in rooms that always feel cold underfoot.

Suspended Timber Floors#

Older UK homes often have timber floors suspended above a void. These are the easiest type to insulate. Rigid insulation boards or mineral wool batts are fitted between the joists from below, either by lifting floorboards from above or by accessing the void through an underfloor space.

If your home has airbricks around the base of the walls, the underfloor space must remain ventilated. Insulation should sit between the joists, not block the airflow beneath.

Solid Concrete Floors#

Insulating a solid concrete floor is more disruptive because it usually means adding a layer of rigid insulation on top of the existing floor, then laying a new floor surface over it. This raises the floor level, which can affect door clearances and skirting boards.

This type of work is best done when you are already replacing a floor covering or carrying out a major renovation.

Costs and Savings#

Floor insulation typically costs £1,000 to £2,500 and saves up to £115 per year on energy bills for a semi-detached house. The payback period is longer than for loft or cavity wall insulation, but the comfort improvement is immediate.

Draught-Proofing#

Draught-proofing is one of the cheapest and quickest ways to reduce heat loss. Cold air entering through gaps around windows, doors, letterboxes, loft hatches, and chimneys forces your heating system to work harder.

Common Draught Sources#

• Windows and doors — Gaps between the frame and the opening can be sealed with self-adhesive foam strips or brush strips. Sash windows benefit from specialist draught-proofing kits.
• Chimneys — An unused open chimney can lose a surprising amount of heat. A chimney draught excluder (a balloon or cap) blocks the flow of warm air up the flue while still allowing some ventilation.
• Letterboxes — A simple brush-style cover on the inside of the letterbox reduces cold air ingress.
• Loft hatches — Fit draught-proofing strips around the frame and ensure the hatch sits firmly in place.
• Floorboard gaps — Gaps between floorboards and at the skirting board edge can be filled with flexible filler or sealant.

Costs and Savings#

Professional draught-proofing of a typical house costs between £100 and £350. DIY draught-proofing is even cheaper — a pack of self-adhesive foam strips costs just a few pounds. Annual savings of up to £125 are possible, giving a very short payback period.

Double Glazing#

Replacing single-glazed windows with double or triple glazing reduces heat loss through the glass and also cuts down on draughts and external noise. Modern double-glazed units have an insulating layer of argon gas between two panes and a low-emissivity coating to reflect heat back into the room.

Costs and Savings#

Replacing all the windows in a semi-detached house with A-rated double glazing typically costs between £3,000 and £7,000. The Energy Saving Trust estimates annual savings of around £120 when replacing single glazing.

The payback period for double glazing on energy savings alone is long — often 25 years or more. However, double glazing also reduces condensation, noise, and maintenance compared to older single-glazed timber frames, so the full value extends well beyond the energy saving figure.

For a comparison of the leading installers and current deals, see our guide to the best double glazing companies in the UK for 2026.

Choosing the Best Insulation for Your Home#

The right insulation depends on your property type, its current condition, and your budget. Here is a practical decision framework.

If your home is uninsulated, prioritise in this order:

1. Loft insulation — cheapest, fastest payback, often eligible for free grants
2. Cavity wall insulation — high impact, low cost, professional installation required
3. Draught-proofing — quick wins around doors, windows, and chimneys
4. Floor insulation — worthwhile if floors are noticeably cold
5. Solid wall insulation — expensive but transformative for pre-1920s homes
6. Double glazing — consider when existing windows are at end of life

For a deeper comparison of materials and performance by insulation type, see our article on the best insulation for UK homes in 2026.

Insulation Grants and Financial Support#

The UK government offers several schemes that can reduce or eliminate the cost of insulation, particularly for low-income households and energy-inefficient properties.

Great British Insulation Scheme#

The Great British Insulation Scheme targets homes in council tax bands A to D (in England) with an EPC rating of D or below. It provides funding for loft insulation, cavity wall insulation, and other measures. Some homeowners qualify regardless of income, while others must be receiving qualifying benefits.

ECO4 Scheme#

The Energy Company Obligation (ECO4) requires large energy suppliers to fund energy efficiency improvements in eligible homes. This scheme focuses on low-income and vulnerable households. Qualifying measures include loft insulation, cavity wall insulation, solid wall insulation, and floor insulation.

Home Insulation Grants#

For a full overview of every available grant, eligibility criteria, and how to apply, see our detailed guide to home insulation grants in the UK for 2026.

Local Authority Schemes#

Many local councils run their own insulation programmes, sometimes with more generous eligibility criteria than the national schemes. Check your council website or contact them directly to find out what is available in your area.

Cost vs Savings: Complete Comparison#

The following table brings together the key figures for every insulation type, helping you compare the investment and return side by side.

Frequently Asked Questions#

Next Steps#

Insulation is the foundation of an energy-efficient home. Whether you are starting with a cheap loft top-up or planning a major solid wall retrofit, every measure reduces your bills and improves comfort.

Here is how to get started:

1. Check your loft — Measure your existing insulation depth. If it is below 270mm, topping up is quick and affordable.
2. Identify your wall type — Find out whether you have cavity or solid walls, then explore the right insulation option.
3. Check your grant eligibility — Use the grant checker above or visit our insulation grants guide to see if you qualify for free or subsidised insulation.
4. Get quotes — For professional installation, get at least three quotes from certified installers registered with CIGA, the BBA, or NIA (National Insulation Association).

For further reading, explore our detailed guides:

• Loft Insulation Guide: Costs, Savings and How to Install
• Best Insulation for UK Homes in 2026
• Best Double Glazing Companies in the UK for 2026
• Home Insulation Grants UK 2026
• Great British Insulation Scheme Explained