In Response to Market Calls, Wetherby Unveils InteriA A-Rated Internal Wall Insulation System

Wetherby Wall Systems, part of the ROCKWOOL Group, has launched InteriA, a next-generation Internal Wall Insulation (IWI) system developed in response to increasing demand for enhanced fire safety and compliant retrofit solutions in line with today’s best- practice.

Internal Wall Insulation has long been recognised as a vital measure for improving the thermal performance of solid wall properties, particularly where external wall insulation is restricted by planning requirements, heritage considerations, or site access. Yet, the market has lacked a fully developed solution that can combine high fire resistance with the moisture management now identified as best practice by government guidance.

InteriA has been designed to meet both challenges head on. Constructed from A-rated components, the system offers strong fire performance, aligning with today’s more stringent safety expectations. In parallel, its moisture-open design reflects advice from the Department for Business, Energy & Industrial Strategy (BEIS), which highlights that the lowest-risk IWI solutions are those that allow walls to dry to both sides, minimising the risk of condensation and safeguarding long-term building health.

“InteriA has been developed in direct response to what the industry was asking for: an A-rated, moisture-open internal wall solution,” said Joe Ragdale, Technical Director at Wetherby Wall Systems. “By combining robust fire performance with safe moisture management, it provides confidence for specifiers and housing providers that compliance, resident safety, and building durability are all addressed within one system.”

The InteriA build-up has been engineered with retrofit practicality in mind. A slim profile ensures compliance with UK refurbishment U-value targets using just 100mm of insulation, maximising internal space while delivering a step change in thermal efficiency. For residents, the result is warmer homes, reduced energy bills, and improved comfort levels.

Installation has been designed to be quick and minimally disruptive, making it particularly suited to occupied dwellings and phased upgrade programmes. This ensures that Housing Associations, Utility Companies, and Managing Agents can roll out retrofit schemes efficiently while keeping inconvenience to tenants to a minimum.

Now part of the ROCKWOOL Group, Wetherby Wall Systems combines its UK expertise with the group’s global innovation in stone wool insulation. The InteriA system benefits from this partnership by offering:

• Fire Safety – Built from A-rated, non-combustible stone wool components.
• Moisture Management – Breathable design reduces risks of damp and mould.
• Thermal Efficiency – 0.034 W/(mK) thermal conductivity provided by the main insulant.
• Sustainability – 60-year design life, fully recyclable materials, and RockCycle waste recovery.
• Compliance – Supports the requirements and recommendations of the BEIS best practice guide and PAS 2035.

For Housing Associations, InteriA provides a reliable way to improve building stock while ensuring resident safety. For Energy Providers, it offers a route to delivering energy efficiency targets and supporting government-backed retrofit initiatives. For Managing Agents and Certification Bodies, the system represents a tested, compliant option that reduces programme risk while simplifying quality assurance.

InteriA has been carefully developed from A-rated components to give specifiers confidence today. It marks a significant step forward for IWI solutions, offering a balance of fire performance, moisture safety, and sustainability in one system.

For technical support or project enquiries, contact Wetherby Wall Systems on 01942 717 100 or info@wall-systems.co.uk, or visit www.wall-systems.co.uk.