The Passivhaus diaries, part one: Green for go

Early lessons and preparations

Geoff and Kate Tunstall first approached the Green Building Store (GBS) two years ago wanting to build a cost-effective, energy-efficient retirement home on a plot of land in their garden. Following some initial meetings with myself they were encouraged to go down the German Passivhaus route.

To take the project forward, GBS enlisted the help of energy consultant Peter Warm and Huddersfield architect Derrie O'Sullivan. Getting the right design has taken a couple of false starts, with the initial L-shaped design with conservatory rejected for failing to perform to Passivhaus standards, after modelling with Passivhaus Planning Package (PHPP) software.

A subsequent design, following a more classic Passivhaus shape - rectangular, with the longest side facing south for optimum solar gain - met the desired 15 kWh/m²/annum level for space heating. The Tunstalls' desire for a conservatory was incorporated into the building envelope as an integral solar space, with exterior brise soleil to minimise overheating. The project will also use super insulation, stringent airtightness, maximum use of passive solar gains and a mechanical ventilation and heat recovery system to achieve the 15 kWh/m²/year space heating demand.

After two long years in the pipeline we finally begin on site this week, starting with excavation work and preparation of foundations. A JCB has been booked and we're hoping the weather will be kind to us.

The last couple of weeks have probably been the most important in terms of making sure that the project goes smoothly. Our site foreman Jude Wilson and I have been working on the detailed drawings, based on Derrie's original designs. For a Passivhaus construction, it is vital that the pre-build drawings are completely accurate so that all the team from suppliers to builders on site are 'singing from the same hymn sheet'.

Last week we also held a training day on Passivhaus construction for the entire building team. Though we are very experienced at building energy efficient homes, this is our first Passivhaus and I wanted everyone to understand the significance of the project and the particular areas (such as the avoidance of thermal bridging and maximisation of airtightness) that we need to watch out for. I always aim for a partnership approach to construction – encompassing everyone from our clients and architect to those on site - and try to avoid the 'blame culture' common in the construction industry.

To visit the Green Building Store, go to http://www.greenbuildingstore.co.uk/denbydalehouse.php.