The Autonomous house
Alu2wood Passivhaus windows specified for groundbreaking project
The Autonomous House is an ambitious and inspiring eco-building project undertaken by Mike Coe and Lizzie Stoodley in Cropthorne, Worcestershire. The project aims to be ‘beyond Passivhaus’ using a thermally massive structure with ultra-insulation to eliminate the need for any heating or cooling system. This ‘zero heat’ strategy exceeds the German Passivhaus standard, with a predicted space heating requirement of just 5 kWh/m²/yr.
The project was inspired by eco-architects Brenda and Robert Vale (authors of The New Autonomous House), who built the Southwell autonomous house in Nottinghamshire in the mid-1990s. The design aims for the Cropthorne House are based on those of the Southwell house, including:
- The house should make minimal demands on the environment during construction, its working lifetime, and ultimate demolition/disposal.
- The house should obtain all of its servicing from its immediate surroundings, i.e. it should obtain water, heating, lighting and dispose of its waste all within the site on which it is built.
Optiwin Alu2wood windows from Green Building Store were specified for the project. Mike Coe explains the choice of Alu2wood:
“We came to the Alu2wood windows by quite a convoluted route. We wanted a timber/ aluminium composite Passivhaus window for minimal maintenance and at the time we were looking there were really only two options available – one of which was Alu2wood. We’d been very impressed when we saw them installed at the AI Passivhaus underground house in the Cotswolds, and preferred the Optiwin frame which was slimmer and less chunky than the alternative. We were also drawn to Green Building Store’s technical expertise – especially Chris Herring who is very knowledgeable about high performance windows. Chris was able to work with our energy consultant David Olivier on a unique glazing specification for the south elevation.
As we wanted the house to have a zero heat requirement – even more efficient than the Passivhaus standard – we needed to be able to maximise the solar gain from the south elevation. The standard Alu2wood specification was perfect for the north, west and east elevations but for the south elevation we needed a different type of glazing to bring extra heat into the house. David and Chris were able to offer really good technical advice, and in collaboration with the Optiwin factory in Austria produced a unique glazing specification with 95% argon fill and special coatings to maximise the solar gain (g-value) – with just a minimal sacrifice to the U value of the windows. We're really pleased with the design of the Alu2wood windows . The inside timber looks great and the low maintenance exterior aluminium cladding works very well too. We still prefer the Alu2wood’s slimmer frame, and with the windows fully installed by Green Building Store's own excellent installation team, we don't have any doubts that we made the right decision“
More information
The Cropthorne autonomous house www.cropthornehouse.co.uk
Neill Lewis, Architect, Tel: 01684 563356, email: neill.lewis@aecb.net
David Olivier, energy consultant www.energyadvisoryassociates.co.uk
Optiwin Alu2wood windows, Green Building Store, www.greenbuildingstore.co.uk
