How Much Does Home Insulation Cost in the UK? A Complete Breakdown

19 July 2023

Insulating your home is one of the most cost-effective improvements you can make, cutting energy bills and making rooms warmer in winter and cooler in summer. But costs vary widely depending on the type of insulation, the size of your property, and whether you tackle the job yourself or hire a professional. Here's a practical breakdown to help you budget.

Loft Insulation: The Easiest Win

Loft insulation is usually the cheapest and quickest project on the list. Most UK homes benefit from topping up to the recommended depth of around 270mm of mineral wool roll insulation.

Blanket (roll) insulation: relatively inexpensive per roll, and a confident DIYer can lay it in a day or two over a typical semi-detached loft.
Blown-in (loose-fill) insulation: needs professional installation, as the material is blown into the loft space with specialist equipment.
Rigid board insulation: more expensive per square metre but useful where space is tight or for insulating between rafters.

If you hire a professional, labour will add a meaningful chunk to the bill, but the job is typically finished within a day. Because the materials themselves are modestly priced, loft insulation often pays for itself within a few years through lower heating costs.

Cavity Wall Insulation

If your home was built after the 1920s in most of England and Wales, it may have cavity walls — two layers of brick or block with a gap in between. Filling that gap with foam or bead insulation is a job strictly for registered installers, who must first assess that your walls are suitable and that the cavity is clear.

Costs depend heavily on the size and shape of the property, with detached homes costing more than terraces or flats. It's worth getting quotes from several installers and checking that they offer a long-term guarantee, as poorly done cavity wall insulation can cause damp problems that are expensive to put right.

Solid Wall Insulation: A Bigger Investment

Older homes with solid brick or stone walls can't have cavity fill, so the insulation goes on the inside or outside of the wall instead.

Internal vs External Solid Wall Insulation

Internal insulation involves fixing insulated plasterboard to the inside face of external walls. It's generally cheaper than external work, but it reduces room sizes slightly and means skirting boards, sockets and radiators may need to be moved.
External insulation wraps the whole house in an insulating layer finished with render or cladding. It costs considerably more, involves scaffolding, and may require planning permission in some areas — but it doesn't eat into living space and refreshes the home's appearance.

Solid wall insulation is by far the most expensive of the common options, so it's usually only worth doing alongside other renovation work or when energy savings over the long term justify the outlay.

Other Insulation Projects Worth Considering

Don't overlook the smaller jobs, which deliver real savings for modest spending:

Draught-proofing around doors, windows and letterboxes — one of the cheapest improvements you can make.
Floor insulation, either by lifting floorboards and fitting mineral wool between joists, or by insulating a solid ground floor (a bigger, more disruptive job).
Insulating hot water tanks and pipes with jackets and foam sleeves — very cheap and instantly effective.
Secondary or double glazing to reduce heat loss through windows.

These smaller measures often cost very little relative to the comfort they add, and they're ideal projects to complete before winter.

Reducing the Cost: Grants and Support

Before you pay full price, check whether you qualify for financial help. Government-backed schemes aimed at improving energy efficiency in lower-income and less energy-efficient homes have, in recent years, offered funding for loft, cavity wall and solid wall insulation. Energy suppliers also have obligations to support efficiency improvements, and some local councils run their own schemes.

It's also wise to:

Get at least three quotes from reputable, accredited installers.
Check for applicable VAT treatment, as some energy-saving materials attract reduced rates.
Ask about guarantees — many reputable installers offer cover lasting decades.

The Bottom Line

Loft insulation is affordable and often the best return on your money; cavity wall insulation sits in the middle; and solid wall insulation is a serious investment best planned alongside other works. Whatever route you take, start with a professional assessment or a home energy survey so you spend where it counts — and enjoy a warmer, cheaper-to-run home for years to come.