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Lower Watts House

The House

Built to AECB Silver/Passivehaus Standard, Lower Watts House was designed and built to use one-quarter of the average energy of homes of this size – to prove that it could be done. No expensive technologies or gizmos – just thought and careful application of key principles.

The house is in a Conservation Area so had to conform to traditional build form and type so is built of Cotswold stone.

When we bought the plot in 1992, it already had the foundations of a house running from north to south across the plot. We demolished half the foundations to turn the main living space to face south and south-west to make the post of passive solar design – for good daylighting and solar gain.

Our main current problem is that our grown-up children will soon leave us with a large house with its low carbon footprint – but shared only between two people – so losing some of the benefit.

Latest case studies:

Vital Statistics

Completed in January 1992.
290m2, detached, 5 bedrooms, and two studies, in half an acre, where we also try to be close to self-sufficient in vegetables and fruit.

The second study is a room in the roof, which is a fully plastered out loft with one room for storage, and the other multipurpose.

Annual energy usage

Gas: 54kWh/m2 yr
Electricity: 11kWh/m2 yr (reduced to 9 last year)
CO2: 17kg/m2 yr

About us and why we did it

We are both energy consultants and environmentalists. We are always aware of energy use – generally wasteful – and when we were looking at a house to buy when we moved to Charlbury - we felt that we could not buy an old, leaky house with high energy use.

Heating and power

We have a gas condensing boiler that works with water direct from the mains. This was unusual at the time.

Mains electricity

The boiler is currently under test by EST. It appears to be around 90% efficient.

We are about to do a study to establish whether running the boiler 24-hours/day (with the boiler fan using electricity all that time) leads to lower CO2 emissions overall than turning off the heating system overnight.


The house has thick insulation in the floor, walls and roof. All windows are triple-glazed.

Tips and Tricks

An energy consultant clled David Ollivier assisted the architect with all aspects of the design as they impacted on its energy.

015698 780868

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