Case Study

House: Wellington Lane

Project type: Retrofit & Passivhaus Planning Package (PHPP) calculations

Property: Terraced ex-industrial unit

Size: 160 sqm

Location: Bristol

Overview: In 2007, James & Poppy bought this 1930s light industrial unit. They were immediately drawn to the big open spaces with high ceilings and set about making it their home. Motivated by the need for more usable living space to accommodate their growing family, they decided to extend and refurbish the building and reduce the energy consumption, aiming for the AECB Silver Energy Standard.

As a structural engineer specialising in timber construction, James designed the conversion and retrofit himself, with energy calculations using the Passivhaus Planning Package (PHPP) done by Earthwise. A ‘fabric first’ approach was adopted, which focuses on high levels of insulation and airtightness. The walls, roof and floor have all been insulated far beyond current Building Regulations. An Intello airtight membrane has been used on the walls to increase the airtightness to 0.83 m3/hr/m2. A Paul Focus 200 Mechanical Ventilation with Heat Recovery (MVHR) system supplied by the Green Building Store has been installed to provide fresh air and maintain good indoor air quality.

The building work was done by Earthwise and took five months. The work involved demolition of most of the existing workshop, and building a second storey and new timber frame walls. High performance phenolic foam insulation was used throughout with triple glazed windows. Other materials include wooden floors, stone tiles, exposed brick, smooth plaster and industrial roofing sheets.

Timber award: Timber features prominently in the new building.  Bespoke curved glue laminated (Glulam) timber beams were designed as the main load bearing roof structure.  Glulam beams are small pieces of timber, glued and laminated for increased strength and can be used to replace steel as load bearing elements and can be left exposed. The use of Glulam maximized the height of the new storey without unnecessarily overshadowing neighbours’ gardens. The eaves at the front of the building have an overhang to give good shading in summer to prevent overheating, but allow the low winter sun to flood in, so the building can benefit from solar gain in the colder months.  For its use of timber, the project won the Best Self Build Project in the Structural Timber awards in 2016.

Performance: James recently said, “After living in the house for a year, we can see that gas bills have significantly reduced and our energy requirements are in line if not better than those predicted by the PHPP model.  The outcome of this project was hugely successful. We now live in a home which always feels warm – requiring only one hour of heating per day even in the depth of winter.”