New build Passive house in the Chew Valley

Summary of works: Site management, wood fibre insulation, drylining, joinery, bathroom fitting, kitchen fitting, airtightness, roofing, shadow gap details 

We provided site management, carpentry, drylining, cladding and cabinetry for the principal contractor, Earthwise Construction, in the build of this new passivhaus in the Chew valley. 

The insulated timber frame was built in modules off-site and erected in a matter of days by an external contractor. 

The heating for the entire house (all 240 sq m) is provided by just 3 towel rails and a small radiator in an airing cupboard. These are powered by an air source heat pump. Heat is retained due to the thick, continuous insulation, and the airtight membrane. An airtightness of just 0.4m3/(h.m2) was achieved (new buildings commonly achieve 7m3/(h.m2) or higher – ie they leak 17 times as much air as this one!) 

The limit for a standard new build is 7 cubic metres per hour. The MVHR (mechanical ventilation and heat recovery) ducting system extracts warm moist air and replaces it with warm fresh air throughout the house. 

The exterior was fully clad in wood fibre insulation, then rendered with a Baumit modern render system. The roof has a large solar array, bringing the house close to self-sufficiency in power. There is a car charging port on the side of the house, a good way to use excess solar power. There are plans to install battery storage later.  

There is a polished eco-concrete floor throughout the large ground floor (approx. 120 sq m!) and coordinating this with the flush skirting detail, plus the shadow gap details around the doors was a logistical challenge, but the results are stunning. The frames are made from Columbia pine (douglas fir). Doors are 2.4m in height! 

The kitchen was fitted with standard units but finished off with a bespoke bookcase and upstand at the end, and a large panel made from a single, solid slice of sequoia that was felled (out of necessity) in the clients’ previous garden. 

All 3 bathrooms have wet room showers.