Completed: 2018 Passivhaus homes in Wootton Wawen 

The 14 affordable homes, officially opened by HRH The Princess Royal are built to the rigorous Passivhaus standard.

The homes are a mix of 2 and 3-bed houses and 2-bed bungalows for affordable rent, plus 2-bed houses for shared ownership. 

Built specifically for people with a local connection to the village, the homes met local housing need, while also meeting the parish council’s desire to build homes that incorporate environmental benefits.

Environmental benefits include:  

• Superior levels of insulation and air tightness – radically cutting energy consumption and bills 
• Quality materials and design 
• Ecological zones to promote wildlife and amenity value. 

This scheme also provided:

• community play and exercise equipment
• road improvements and traffic calming
• allotment development
• a community woodland belt. 

Find out more in our Wootton Wawen case study

The scheme was made possible through partnership working with:

The keys to achieving the enhanced heat-loss values required for Passivhaus lay in the ground floor slab design, the junction between the ground floor and external wall, enlarged cavities tightly filled with insulation (leaving no gaps above 2mm) and very careful attention to airtightness and build quality.  

• Bouygues UK, the main developer, found some very smart ways to achieve very high thermal standards, including: 
• 400mm thick ‘Floormate’ floor slab insulation. This is a foam insulation, which formed a raft onto which the concrete floor screed was laid, helping to make the floor slab airtight.  
• Marmox ‘Thermoblock’ blocks were used as the starter course for the internal masonry, which is built off the highly insulated floor-slab. These blocks are effectively a sandwich of insulation, reinforced with concrete ‘legs’, enabling them to transfer load from the slab to the internal walls, without compromising thermal performance.  
• Ancon ‘Teplo BF’ carbon-fibre wall-ties were used to knit the inner and outer leaves of masonry together over a 300mm cavity span. These ties have a very low thermal conductivity in comparison with galvanised steel ties, which virtually eliminates coldbridging. 

A huge part of meeting the Passivhaus standard is achieved through rigorous reporting at key stages of the build, to demonstrate that the required standards of workmanship and attention to detail are maintained.

The project team recognised early on that the supply chain was key to achieving this. We only worked with trades with prior experience of Passivhaus, or a willingness to work with us to learn how to deliver the scheme.  

Experienced support

Bouygues UK also engaged Encraft (now Design Buro), a highly experienced consultant with many Passivhaus schemes completed, to act as a consultant to the delivery team, to provide training and advice, and to help compile and submit evidence.  
 
Bouygues UK used a tool called ‘Field-View’ for reporting progress at key stages The system enabled site progress photographs to be linked to a set of drawings, ensuring that progress was properly logged plot by plot. This data was used to report site progress and quality, and to provide photographic evidence to the Passivhaus assessor.

Regular site inspections by MWK, Eco Design & Construction and back-up inspections by Design Buro further reinforced the diligence required to ensure that the Passivhaus standards of workmanship were met.  

Pilot block policy 

Bouygues UK also adopted a policy of preparing a ‘pilot-block’, which formed a point of concentration for airtightness. Work didn’t progress on the other plots until the pilot block evidenced that the required airtightness, insulation and quality of workmanship met the Passivhaus standard.