Wall Insulation in Brighton & Sussex

Wall insulation is one of the most effective ways to improve the thermal performance of a building. In Sussex, a large proportion of the housing stock — particularly Victorian and Edwardian terraces in Brighton, Hove, and the surrounding towns — is of solid-wall construction. These buildings have no cavity to fill, and their solid brick or flint walls allow heat to escape at a rate roughly three times higher than a modern insulated wall.

Uninsulated solid walls are not just an energy problem — they are a major driver of condensation and mould. When warm indoor air meets a cold wall surface, the temperature drop causes water vapour to condense on the wall, creating the damp conditions in which mould thrives. Insulating the wall raises the internal surface temperature above the dew point, dramatically reducing the risk of condensation.

There are two main approaches: internal wall insulation (IWI), where insulation boards are fixed to the inside face of the external walls, and external wall insulation (EWI), where an insulation layer is applied to the outside of the building and finished with a protective render. Each approach has trade-offs. Internal insulation is less disruptive to the external appearance but slightly reduces room sizes, while external insulation preserves internal space and provides additional weatherproofing but changes the building's exterior.

Choosing the right insulation system for a traditional solid-walled building requires careful assessment. Using the wrong materials — for instance, impermeable foam boards on a breathable lime-mortar wall — can trap interstitial moisture within the wall, causing hidden decay. We specify insulation systems that are compatible with the building's construction and vapour dynamics, ensuring long-term performance without unintended moisture problems.

We carry out a detailed thermal assessment of your property, using thermal imaging and U-value calculations to quantify heat loss and identify the areas where insulation will deliver the greatest benefit. We assess the construction type, existing ventilation, and moisture risk to recommend the most appropriate insulation system.

For internal wall insulation, we typically use rigid phenolic or wood-fibre insulation boards mechanically fixed to the wall with a vapour control layer, finished with plasterboard and skim. For breathable solid walls, we may specify calcium silicate or wood-fibre boards that allow moisture vapour to pass through, maintaining the wall's natural drying capacity. For external wall insulation, we apply expanded polystyrene (EPS) or mineral wool boards to the external face, finished with a reinforced render system in a colour and texture of your choice.

We pay close attention to thermal bridging at reveals, lintels, sills, and junctions — the weak points where heat escapes and condensation concentrates. Every installation includes proper detailing at these critical points, along with any necessary ventilation upgrades to maintain good indoor air quality. Our work is Building Regulations compliant and we can assist with any required planning applications for external insulation in conservation areas.