Wetherby Wall Systems launches InteriA retrofit solutions for solid wall properties in the UK

Wetherby Wall Systems introduces new retrofit solution

Wetherby Wall Systems has launched InteriA, a new Internal Wall Insulation (IWI) system designed to provide A-rated, moisture-open retrofit solutions for solid wall buildings in the UK.

The company, part of the ROCKWOOL Group, confirmed that InteriA was developed in response to growing demand for insulation systems that combine strong fire performance with effective moisture management.

The launch took place earlier this week and marks the latest addition to Wetherby’s retrofit portfolio.

Addressing challenges in insulation for solid wall buildings

Wetherby Wall Systems said Internal Wall Insulation remains essential for improving thermal efficiency where external upgrades are limited by planning, heritage or access constraints.

The company noted that the market has lacked a complete system capable of balancing fire safety and moisture control, both now recognised as central to government best practice guidance.

According to the manufacturer, InteriA is made entirely from A-rated, non-combustible stone wool components, meeting modern safety expectations while incorporating a moisture-open construction that allows walls to dry on both sides.

The company explained that this approach aligns with advice from the Department for Business, Energy & Industrial Strategy (BEIS), which identifies moisture permeability as key to minimising condensation and safeguarding long-term building health.

Compliance, performance and sustainability

Wetherby Wall Systems said InteriA delivers a slim profile that enables refurbishment U-values with 100mm of insulation while supporting compliance with PAS 2035 and the Building Safety Act.

The system offers a 60-year design life, uses recyclable materials and can be integrated into the RockCycle waste recovery scheme.

The firm stated that installation has been engineered for minimal disruption and improved practicality, making it suitable for occupied dwellings and large-scale retrofit programmes.

Industry response to new A-rated system

Joe Ragdale, Technical Director at Wetherby Wall Systems, said: “InteriA has been developed in direct response to what the industry has been calling for: an A-rated, moisture-open internal wall solution.

“It has been carefully designed to give specifiers, housing providers and programme managers confidence that compliance, resident safety and building durability are all addressed within one system.

“By combining safety, sustainability and compliance, InteriA represents a significant step forward for IWI solutions and will play a valuable role in helping the UK meet its carbon reduction and energy efficiency targets.”

Relevance for fire and safety professionals

Fire engineers, housing providers and building services consultants involved in retrofit and refurbishment programmes will find this development directly relevant.

The InteriA system’s A-rated, non-combustible composition and alignment with the Building Safety Act address ongoing concerns over material compliance in occupied residential properties.

For specifiers, the inclusion of moisture-open design principles consistent with BEIS guidance supports safer long-term building performance by reducing risks associated with trapped moisture and condensation.

Programme managers and compliance officers overseeing decarbonisation or energy-efficiency schemes can also apply InteriA in cases where external insulation is not feasible, ensuring fire safety standards remain consistent with PAS 2035 expectations.