The Positive House

Phil Thornton

7 min read

Old Coal to Energy Positive

Can a home for a car collection positively reverse climate change? When we were approached to build a dream garage for a Mercedes Benz car collection, on the site of an old coal stockyard in Woking, the first thought was how bad the combination of old coal and cars were for our carbon footprint.

The response was to design a structure that would not only embody carbon in its structure but go on to create more energy than it uses. Not simply aim for the usual passive haus or carbon-neutral standards but to improve on them and more. In this house, the client switches the building on and the energy companies pay him.

How do we do that:

1. All the roofs face north or south. South-facing roofs are covered in solar panels and north-facing roofs let in a neutral north light, reducing the need for artificial lighting whilst avoiding sunlight entering the building to cause heat gain. Four roofs over the house create a sawtooth effect and each has a sedum planted green gutter between.

2. Insulation, insulation and more insulation. Insulation outside the walls, insulation between the wood frame uprights and more insulation inside the walls. The walls inside are finished with clay plaster to soften the acoustics and give a high thermal mass. The outside-in zinc to keep the sunlight and rain off the insulation. It’s a bit of a thermos flask – but full of cars

3. Air-tightness. The insulation is backed up by a continuous airtight membrane called passive purple. Designed to entirely stop drafts and linked to a radon membrane at ground level to stop any possibility of old coal vapours coming in.

4. Heat recovery. All the rooms are supplied with fresh air from heat recovery ventilation systems.

5. There is a state-of-the-art ground/roof source heat pump which works on the roof through the photovoltaic covered roof tiles – the heat is pumped whether the sun is shining or not and when the sun shines the photovoltaic panels are generating electricity to power the pump. Any excess goes into battery backup and the leftover is exported back to the grid.

The Positive House is a pioneering building that reverses the usual way of thinking about building. It might be an Old Coal Yard and the shape might be inspired by old railway sidings and sheds but the building is anything but old fashioned. Creating more energy than it uses, it is a model for future construction techniques and technologies that will help in a small way to reverse the excessive emissions of the fossil fuel era. So the cars are all now fossils in a collection. They might go out very occasionally but in reality, they are sitting there in a private museum to be looked at and admired as beautiful but obsolete objects.

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