Home Insulation and Energy Efficiency

Over 47% of the walls in our homes are thought to be uninsulated, whilst around 34% of lofts have insufficient levels of loft insulation. The UK has a long way to go to insulate its housing stock and improve energy performance levels.


The UK has a diverse housing stock comprising of buildings with lots of different construction types and levels of insulation. The housing stock includes everything from older properties with solid walls (such as Victorian houses) to more modern properties with cavity walls, some of which are the leakiest and worst-performing buildings in the whole of Europe.

In total, there are around 29 million residential properties in Great Britain. Using Government data, roughly 71% of these are classed as having cavity walls whilst the remaining 29% have solid walls constructed of solid brick, stone or other non-standard construction types. Additionally, nearly 87% of properties are thought to have a loft space.

According to the latest household energy efficiency statistics, only 70% of cavity walls are estimated to have cavity wall insulation installed, whilst only 9% of solid walls are estimated to have some form of internal/external solid wall insulation.

Levels of insulation in GB housing stock

This means that over 47% of the walls in our homes are uninsulated. Meanwhile, only 66% of houses with lofts are considered to have sufficient levels of loft insulation (>= 125mm). When combined with the fact that over a third of the energy used in our homes goes in space heating, insulation plays a significant part in the energy balance of buildings and improving home energy efficiency.

Types of home insulation

Cavity Wall Insulation

Cavity wall insulation is where there is insulation added to the cavity between the internal and external layers of a wall's construction. Modern new-build houses will have wall insulation added during construction as required by building regulations. But many older properties with cavity walls, typically constructed from the 1920s to the 1990s, may have no wall insulation at all.

Cavity wall insulation is installed by drilling holes in the external brickwork and injecting insulating material into the cavity of a wall. Once the insulation has been added, the holes will be filled with cement to match the original mortar. This is a specialist job carried out by cavity wall insulation installers after careful inspection and assessment.

Various insulating materials are used in cavity wall insulation. Fibre insulation is where fibreglass or mineral wool is blown into the cavity using compressed air. Bead-based insulation uses polystyrene beads or granules also blown into the cavity but then bonded together using a resin. Finally, foam insulation uses injected foam mixed using two chemical components which expands to fill the cavity.

Solid Wall Insulation

Where a property has solid walls, there is no cavity inside the wall so it is not possible to use the same cavity wall insulation techniques. Instead, solid wall insulation will mean either adding external insulation to the outside surface of a house or internal insulation to the inside surface of walls.

External Wall Insulation (EWI) comes in various forms but will typically require a layer of insulation board (EPS or XPS polystyrene board) or mineral wool/fibre insulation attached to the external wall surface. The insulation is then be covered using either cladding or render to thermally separate the solid wall from the elements.

Internal Wall Insulation (IWI) uses a number of ways to insulate the internal surface of heat loss walls. Internal wall insulation methods include dry-lining walls or using insulated plasterboard or plaster to retain heat within a building. All forms of internal wall insulation inevitably cause a slight reduction in internal space.

Loft Insulation

Loft insulation is one of the simplest types of insulation to add to houses and is an easy way for homeowners to reduce heat loss through roofs. Roof and loft insulation mean adding insulation material to the roof, attic or loft space of a building trapping heat within and preventing it from escaping through the roof. As we all know warm air rises, so adding loft insulation provides an easy way to reduce energy consumption and lower energy bills.

Insulating lofts and roofs involve adding rolls of glass fibre insulation or polystyrene-based insulation board internally either between the joists of a loft floor or between the rafters of the roof space, or sometimes both. It is a fairly simple process that can be undertaken by the homeowner themselves or by qualified tradespeople.

Measuring levels of insulation

Performance of building elements is determined by U-values or thermal transmittance. Our unique products allow U-values of walls, floor and ceilings to be measured accurately allowing assessment of insulation performance and heat loss both pre and post-insulation.

Heat3D mobile app and FLIR ONE Pro on an iPhone

Heat3D Infrared U-value Measurement

An innovative mobile app that allows you to precisely measure heat flow and U-values of walls using a low-cost, quick and non-invasive method.

Learn more about Heat3D Infrared U-value Measurement
ISO 9869 U-value measurement system

ISO 9869 U-value Measurement System

System for measuring in-situ U-values of walls, floor and ceilings according to the ISO 9869 methodology.

Learn more about ISO 9869 U-value Measurement System

Given the low levels of home insulation and record energy prices, there is clearly a need to insulate the UK's housing stock even further especially with the planned move away from gas boilers to heat pumps which requires well-insulated buildings to work efficiently. Many forms of insulation are available for homeowners to add to their homes, some of which are covered under Energy Company Obligation (ECO) schemes with grants available.

How to measure levels of insulation

The level of performance and insulation of a wall, floor or roof is determined by its U-value. U-values are a metric that defines the ability of a building element to transmit heat from a warm space (inside a house) to a cold space (outside). Adding insulation to a building will lower the U-value and mean there is less heat loss through a particular building element.

Modern new-build houses are designed with insulated cavity walls with a U-value under 0.3 W/m²K. Whilst old uninsulated solid brick walls will have U-values anywhere up to 2.0 W/m²K. Measuring U-values both before and after adding insulation can help determine what level of insulation needs to be added and what the performance improvement was after installing insulation.

Heat3D Rapid U-value Measurement

Heat3D is a simple mobile app that uses infrared thermography to measure U-values and makes it more accessible than ever before. It's a low-cost, easy-to-use and quick measurement technique that enables quantified U-values that are more accurate than relying on visual inspections alone.

Using Heat3D to measure U-values and insulation levels

In-situ U-value Measurement Kit

Alternatively, our in-situ U-value measurement kit delivers high accuracy and quantified U-values of building elements according to the ISO 9869 standard. It uses heat flux plates that are attached to the inside surface of walls, floors and ceilings to record heat flow and U-values precisely over a number of days.

Measuring U-values and insulation levels using heat flux plates