Roofline Closure Systems: a Retrofit Professionals' Forum

Roofline Closure Systems Presentation

On 10th October, Permarock’ Technical Director Dr Jeremy Richings appeared as one of the expert speakers at a webinar hosted by the Retrofit Academy. Titled “Roofline Closure Systems for External Solid Wall Insulation”, the presentation took place as part of a Retrofit Professionals' Forum.

The webinar began with an introduction by Peter Rickaby, who is well-known for his  extensive background in domestic energy efficiency and sustainability. Peter chaired the BSI Retrofit Standards Task Group from 2016 to 2023, and was the Technical Author  for PAS 2030:2019 and PAS 2035:2019.  In his introduction, Peter explained that the use of eaves and verge trims with EWI had been prohibited by PAS 2030:2019 and PAS 2035:2019, as a consequence of a series of technical failures.

Peter introduced Jeremy Richings of Permarock and Andrew Champ of SWIGA, both of whom he noted had been closely involved in the development of the new guidelines for Roofline Closure Systems. Together, Jeremy and Andrew delivered a 45-minute segment titled “The Response: The Roofline Closures Approach.” They explained the background to the issue, including why the use of ‘verge trims’ had previously been prohibited, and the steps taken by the Working Group to ensure that a new and versatile solution could be devised and approved.

 

Key points from Jeremy’s presentation included:

 

  • Extending rooflines above EWI remains the best and preferred technical solution. However, certain constraints can render it impractical.
  • PAS2030/2035 requires compliance with “EWI Weathering and Thermal Bridging Details” published by SWIGA, so a new PAS-compliant approach to roofline closure systems (RCS) had to be added.
  • At the insistence of the BSI Retrofit Standards Task Group, this was only approved after testing to confirm the expected performance and identify any installation issues.
  • This testing sought to:
    • ensure reliable weathering resistance, with multiple layers of defence;
    • define a minimum level of thermal resistance to prevent thermal bridging;
    • minimise demands for future maintenance;
    • ensure that any solution is backed by a quality standard for installation, including training and record-keeping.
  • The Working Group developed a series of standard details to illustrate scenarios in which properly designed RCS could reliably be used.
  • Live trials on solid-wall properties provided good evidence of the fitness of the standard design details. The trials were subject to intensive study and backed up by detailed records. Many lessons were learned. For example, they highlighted the importance of completing necessary rectification works before installing any RCS.
  • Trials also showed that an approach based solely on standard details would not be sufficient to cover all scenarios that might be encountered on site.
  • Therefore, the industry needed a set of ‘Design Principles’ that would enable designers to develop their own solutions, subject to meeting specific criteria. Examples include:
    • Ensuring a minimum level of thermal insulation;
    • Providing at least two lines of protection against rainwater penetration;
    • Ensuring minimum overlaps at junctions / connections;
    • Requiring external corner connections to be pre-fabricated
    • Limiting the use of site-fabricated components generally.
    • Not relying on mastics as a primary weather barrier;
    • Adhering to minimum material specifications to prevent the ‘cheapening’ of design solutions.

Andrew Champ then continued the presentation, noting how valuable the trial period had been, in terms of the lessons learned. He then summarised the solutions developed. He noted that:

  • There are two routes to compliance: either using the standard details, where relevant, or creating bespoke designs following the guidance set out in the RCS Design Principles.
  • The team developed a process map for RCS design and installation, which must always begin with an individual property survey.

 

Andrew went on to explain the various new elements of the revised Weathering Guide – i.e. the “August 2024 update”, which features the new standard details, minimum materials specifications, the process map and a Design Principles Installation Checklist. (Note: a copy of the guide can be downloaded from the Roofline Closure Systems section of our Technical Hub.)

 

This concluded the formal presentation part of webinar. It was followed by a 40-minute Q&A session.