Project Type: Two Storey New Build

Year: 2016

Passivhaus Designer: Andrew Yeats from Eco Arc Architects  

Building Contractor: Sam Nelson (Site Project Manager) 

Frame Construction: Eden Insulation 

Ecological Products Used:

Gutex wood fibreboard

Unilin Durelis VapourBlock board

Warmcel cellulose fibre insulation

pro clima Fronta Humida Membrane


Kendal’s first Passivhaus boasts one of UK’s best airtightness results

This was a project involving a partnership of Cumbrian construction professionals which resulted in the first certified Passivhaus in the Kendal area in the south of the county.  It was constructed using a timber frame made of airtight, insulated panels that were crane erected on site and ready for roofing within just one day.

The 126m2 four-bedroom family home, achieved an initial airtightness test result that was the second-best ever recorded in the UK at the time, 0.11 air changes per hour at 50 Pascals. It was a cause for celebration for the Cumbrian partners behind the build.

Team Involved:                                                                  

Passivhaus designer Andrew Yeats from Eco Arc Architects  
Eden Insulation who constructed the frame
Airtightness materials supplier Ecological Building Systems
Building contractor Sam Nelson, the site project manager. 

Passivhaus Certification Achieved 

The two-storey new-build obtained Passivhaus certification in March 2016. The house, with attached double garage, was designed to fit in with the existing local housing style and is quite traditional in external appearance.

Project Details

The project includes a 4KW/hr PV array on the main roof to provide renewable electricity and to heat domestic hot water via an iBoost, narrow-bore water pipes to reduce energy losses and a waste-water heat-recovery system for the shower.

The panels for the timber frame were fabricated with Metsä Wood Finnjoist I-beams, creating a 300mm thick wall, factory filled with Warmcel cellulose fibre insulation made from recycled newspaper, with a 50mm insulated service cavity. The interior is fitted with Unilin Durelis VapourBlock board, followed by service void and plasterboard, giving the wall a U-value of 0.103.

The outside face of the frame is Gutex wood fibreboard sealed with a Fronta Humida membrane, then a 50mm cavity and rendered blockwork.

The ‘bob tail truss’ rafter roof has Warmcel insulation blown into a depth of 600mm giving a U-value 0.062W/m2K), fitted internally with Unilin Durelis VapourBlock board, service void and plasterboard, and an exterior slate covering.

The floor sits on a 300mm Isoquick insulated raft on compacted hardcore, covered by reinforced concrete, with a tile and carpet finish.

Penny Randell (Ecological Building Systems)

Highlights a rise in demand for air-tightness products and environmentally sensitive materials for insulation and managing moisture.

Here in Cumbria, we’re getting more enquiries from people retrofitting traditional houses, who want to thermally upgrade without trapping moisture in the wall and causing it to degrade.  More natural products like Diathonite, an insulated cork lime plaster, and Calsitherm Climate Board are a great way to insulate and manage moisture within stone walls. Far from being a compromise option for people who put the environment ahead of performance, people are now choosing these kinds of products because they actually work better than some of the mainstream options.”

If you wish to learn more about the airtightness materials used in this project, contact Ecological Building Systems  

Eden Insulation



Certified Passive House
one of UK’s best airtightness results
Certified Passive House