Copper Bottom

A totally original, truly sustainable zero-carbon copper-clad home on an elevated site with stunning views of Oxford’s dreaming spires.

The dynamic sculptural form of the house derives from the uses it serves; form follows function. The design takes what is normally considered a constraint – the need for a passive house to prevent summer solar gain – and turns it into an opportunity for architectural expression.

Copper Bottom is clad in an origami-esque copper carapace. The form is highly modelled to perform very specific roles:it acts as a brise-soleil on three facades and a porch on the fourth. To prevent solar gain the angled roof plane cantilevers far out like a peaked cap barring high summer sun from the large south-facing windows. The skin also pushes out at the waist which creates deep reveals around the east and west facing windows protecting them from low sun in the morning and evening. On the north side of the house the same waistline fold creates a porch for the entrance doors.

The final elements which complete the facetted form of the house are the ears. Just like other parts, they perform a function; the ears are ventilation stacks which will be used to purge the house at night during the summer, drawing the accumulated hot air of the day out and so letting cool fresh night air in.  As such they are an intrinsic part of the heating, cooling and ventilation strategy for the house.

Why copper?

Copper is a very special metal; unlike most others it does not continually corrode as it oxidises. It will basically outlast any building it covers. A metal in abundant supply which, once mined and purified, is as shiny as gold, it then gradually and magically turns a beautiful bright verdigris green and then stays that way forever. 

Freshly minted copper is mostly used for wiring but when it then gets ripped out and melted down, it is used in buildings. So the copper we specify for roofing and cladding is both 100% recycled and 100% recyclable; a perfect material for the circular economy. Copper is elemental, it’s really tough but also malleable, it never corrodes, it has a unique and delightful aesthetic and it’s a sustainable top trump. 

There is a potential catch in that the process of patination can take decades, and on a building like this some parts will go green faster than others; it could look patchy.  But the patination process can be replicated in the factory where copper is rolled out.  The finish on Copper Bottom is less turquoise and more lime than standard pre-patination. Copper Bottom is on a lush site surrounded by mature trees and wildflower meadows; we have chosen a finish which hums along with nature’s song.

A habitable power station

Copper Bottom is fully and holistically sustainable.  With an array of 37 photo-voltaic panels on the roof generating up to 16kW, it is a habitable power station generating renewable energy well in excess of the modest demands of the building itself, which is a highly insulated and airtight passive house. So it is carbon negative and over its lifetime it will make a positive contribution to the planet’s welfare. 

The carbon footprint of the building’s construction is very low. The existing ground allowed for very shallow foundations so there is minimal concrete in the ground, and then above ground the superstructure is all carbon-capturing timber.  The compact and efficient cuboid form is constructed from prefabricated timber panels which are packed with insulation and then clad externally with a system of lightweight timber trusses supporting a plywood skin. This skin is in turn clad in 100% recycled copper. 

When considering a home’s sustainability, location is critical because of the carbon cost of transport. Copper Bottom’s surroundings feel like open countryside but it is actually just on the edge of Oxford, only 15 minutes by bike from the city centre. So the vast majority of journeys are by foot or by pedal; the site is a rural idyll but also very sustainable.

Space, light and view

The heart of the house is the double-height gallery which serves as entrance hall, dining room, and stair lobby. And the focus of that space is the weighty exposed purple brick pier which acts as hearth, stair wall and thermal heat sink, helping to keep the house a steady temperature through the year. 

At the top of the stair there is a landing with a wide oak desk looking down over dining table, through the double-height window to the garden and bosky landscape beyond. This is a Work From Home space which urges the user never to get on their bike and cycle down the hill to the office in town.

The ground floor is open plan, with the lounge, gallery and kitchen flowing into one another as enfilade, each opening onto the elevated terrace through wide sliding doors. This is not a big house, but it is spatially generous and flooded with natural light. The key is that the big windows are all on the south side, bringing in loads of daylight and solar gain in the winter, but they are shielded by the copper sunhat from the high summer sun.

The house is carefully oriented to capture the views across the meadow of the dreaming spires of Oxford which are visible in the far distance and often highlighted by the afternoon sun. The principal bedroom has a wide picture window precisely framing this view from the bed, and the en suite bathroom has a view to rival that of any bathroom in the country.