Wet brickwork can lose twice as much heat as dry masonry – a fact that highlights how moisture plays a crucial but often overlooked role in the performance of solid wall homes.
Around 8 million homes in the UK are built with solid wall construction, yet fewer than 900,000 have been fitted with solid wall insulation. Much of the country’s older housing stock was built before cavity wall construction became standard in the 1930s. While many significantly worse. Brick and mortar are porous materials that absorb rainwater through microscopic pores in the masonry. When these pores become saturated, the wall conducts heat more readily.
FACT FILE: WHY DRY MASONRY PERFORMS BETTER
Research carried out by Portsmouth University found that moisture has a significant impact on the thermal performance of brickwork.
• Wet bricks can lose twice as much heat as dry bricks
• A wet solid brick wall can have a U-value of around 2.79W/m²K
• Keeping masonry dry helps improve wall performance
• Managing rain penetration can support insulation effectiveness. of these buildings remain structurally sound, they were not designed to meet modern energy performance standards.
As energy costs remain high and efficiency regulations continue to tighten, improving the thermal performance of these properties is becoming increasingly important.
Government initiatives such as the Warm Homes Plan and related retrofit funding schemes are also placing greater emphasis on upgrading existing homes to reduce energy consumption and carbon emissions. Solid wall buildings therefore represent a significant opportunity within the UK’s wider retrofit strategy.
WHY SOLID WALLS LOSE HEAT In solid wall construction, a single layer of brick or masonry separates the interior of the building from the outside environment. Unlike cavity walls, which include an insulating air gap, solid walls allow heat to pass more easily through the structure. Research carried out by the Centre for Sustainable Energy suggests that around 50% of the heat lost from a solid wall home escapes through the walls. Improving wall performance can therefore have a major impact on overall energy efficiency. Moisture within the masonry can make this problem
Wet bricks can lose twice as much heat as dry bricks.
Research from Portsmouth University found that wet bricks can lose roughly twice as much heat as dry bricks. A wet solid brick wall can have a U-value of around 2.79W/m²K, meaning heat escapes rapidly through the structure.
Keeping masonry dry therefore plays an important role in improving the thermal behaviour of solid walls. In simple terms, dry walls are warmer walls.
INSULATION AND MASONRY PROTECTION One of the most common retrofit
approaches for solid wall properties is internal wall insulation (IWI). Installing insulation on the internal surface of external walls helps reduce heat transfer and improve energy efficiency.
Popular systems include insulated plasterboard products such as Stormdry EP-Board, or stud wall constructions with insulation installed between framing members. When correctly installed, these systems can significantly improve the thermal performance of solid masonry walls.
However, insulation performs best when the wall behind it remains dry. If rainwater is absorbed into the masonry, the wall can remain damp and heat loss may increase.
This aligns with PAS 2035:2023, which states that the building fabric should be brought into good repair before improvement measures are installed, including resolving water penetration, damp, structural defects and poor pointing, and ensuring the wall is properly dried out.
Vapour-permeable masonry protection treatments such as Stormdry Masonry Protection Cream are designed to reduce rain penetration while allowing moisture vapour to escape from the wall. The cream penetrates into the brick surface and lines the pores of the masonry with a water-repellent silicone barrier. This prevents rainwater from soaking into the wall while maintaining breathability.
By keeping the masonry drier, the wall can retain heat more effectively and insulation systems are able to perform as intended. Reducing moisture levels can also help minimise the risk of interstitial condensation, which occurs when warm indoor air meets colder surfaces within the wall structure.
AN OPPORTUNITY TO IMPROVE BUILDING PERFORMANCE
Improving the performance of solid wall buildings often involves combining insulation with effective moisture management. Internal wall insulation, supported by masonry protection technology, can reduce heat loss while helping to protect the building fabric.
As retrofit programmes expand and greater emphasis is placed on improving existing housing, solid wall upgrades are likely to become increasingly common.
For the UK’s large stock of solid wall homes, keeping masonry dry represents a simple but effective way to support insulation performance and improve the energy efficiency of older buildings. act-developments.co.uk