Project Feature: Baumit OpenSystem provides interior comfort and self-clean exterior for Passivhaus development

Baumit supplied the premium, permeable external wall insulation (EWI) to optimise thermal performance and internal comfort for an award-winning Passivhaus development.

Carrowbreck Meadow in Norwich is an idyllic 14-home development set in acres of glorious woodland. The Passivhaus properties have been designed for optimal sustainability, hence their positioning, which maximises solar gain in winter and prevents overheating in summer.

Described as an ‘important benchmark for future developments’ in terms of design, layout and construction; 43% of the Broadland District Council scheme comprises affordable homes. Contractor, RG Carter supplied the properties, which were designed by architects Hamson Barron Smith.

Baumit’s OpenSystem, a proven, permeable EPS insulation solution that allows walls to breathe and results in better indoor air quality, was applied to 300mm precision-engineered Porotherm blocks. In doing so, Carrowbreck Meadow became one of the first UK housing projects to use blocks of such thickness as part of an innovative clay-block construction.

Baumit’s EWI system includes NanoporTop, which provided the properties’ self-cleaning, pollution-resistant, ready-to-use white render. Extremely durable, dirt and weather resistant, the solution contains Baumit photocat technology to create maximum protection against contamination using the natural power of light. This reduces the need for costly, regular maintenance using aggressive solvents, leading to a sustainable exterior that stays looking cleaner and brighter for longer.

Sarah Lewis, Associate Architect at Hamson Barron Smith, said:

“The homes’ energy performance was key to the success of this project. This was achieved thanks to the buildings’ innovative design, coupled with the skills and experience of the contractor’s on-site teams. Baumit’s OpenSystem played a significant role in improving the properties’ indoor air quality and the project’s overall sustainability. We were very pleased with its performance.”


For the Passivhaus homes, which vary in size from 9.1.2m2 to 180.7m2, every element of their construction was designed to maximise energy performance as well as the comfort and wellbeing of occupants. This included prioritising passive solar shading in the form of trees, deep window reveals and automatic MVHR summer bypass.  These innovations ensured the homes achieved an N50 value air tightness level of 0.45 air changes per hour, which compares favourably to Passivhaus standard of 0.6 air changes per hour.

Completed in October 2016, with the first occupants taking-up residence soon after, the Carrowbreck Meadow project is a stunning example of a high-quality housing development delivering affordable, sustainable buildings. Baumit’s OpenSystem played a substantial part in the homes’ better-than-Passivhaus level of energy performance. It led to the project receiving several architecture and construction accolades, including the RIBA regional and national awards, and the 2018 ‘Large Residential’ UK Passivhaus award.