Spotlight

The Autonomous House

It was rather a thrill for two architects to be asked to produce an article for New Zealand Science Monthly as, up until this moment, very few people had ever suggested that architecture could have anything to do with science.

There is, certainly, environmental science, when discrete problems, such as heat flow through walls or lighting levels in theoretical rooms, can be reduced to the scale of an acceptable laboratory experiment and real results can be inferred from the experimental values measured. Real buildings, however, are very messy objects, growing from mud and, in the UK, very often made of mud (albeit baked), and real, rather messy people tend to live or work in them. Moreover it has been demonstrated that the occupants can affect the way a building behaves, so much so that energy use in apparently identical houses can vary by as much as 300%.

Cost is another important factor; electron microscopes may seem expensive but buildings are not cheap and do tend to take up a lot of space. The upshot of this is that each building is a prototype, and it is never possible to make two inhabited buildings so identical that one can act as a control for experiments undertaken on another.

Nevertheless, as architects interested in how buildings perform and how they might be designed to use less energy, it seemed important to us to try to gain as much information as possible from any building that we were asked to design. However, the experience with the autonomous house that we designed and built in the UK suggested that the scientific community were not interested in the results from one building.

In November of 1993 the autonomous house was first occupied. Built in Nottinghamshire, it was designed and constructed to demonstrate that it was possible to make a house with no carbon dioxide emissions and independent from mains services, that cost no more than a similar building using conventional technologies. We funded it, as the people who were to live in it, and it was built by a local builder after we went out to tender in the usual way.

The envelope of the house was heavily insulated with 250mm in the walls and 500mm in the roof, with windows triple-glazed with smart glass. The fabric inside this insulated envelope was thermally heavy, with walls of plastered dense concrete block and concrete beam and block floors finished with clay tiles. This thermal mass was warmed up in the summer months and used as a heat source in the winter, the other heat inputs coming from solar gain through the windows and the occupants (five people at approximately 100 watts and two cats at 20W). The only other source of heat was a wood-fired stove rated at 4kW. This was installed as a back-up, and also to be lit on days of celebration, such as Christmas, in the overcast and grey UK winter.

In addition, the house collected all its water from the roof, a technology familiar to New Zealand -- though it is interesting to note that Auckland has twice the rainfall of Nottinghamshire. All wastes were also processed on the site through the use of a composting toilet and a grey-water soakaway. Electricity for all energy uses other than heating was provided by a 2.2kW array of photovoltaic panels which were mounted on a south-facing pergola in the back garden.

The house design was based on our earlier work, which had involved the design and construction of a series of medical buildings and social housing which, typically, achieved 80% fossil fuel energy saving over similar insulated masonry construction, at no extra cost. The knowledge brought to the design of the autonomous house was thus essentially empirical and experiential.

Consequently, very little modelling work was done on the performance of the house prior to its construction beyond simple steady-state heat loss calculations. These were then compared to earlier calculations which preceded the other buildings whose performance in use had been determined from collecting copies of the fuel bills of the occupants. A comparison then determined that it should be possible to run the autonomous house without any space heating, relying only on the incidental gains described above. Similarly, very simple examination of our electrical uses in our previous house produced a target for the output of the grid-linked photovoltaic system.

Despite the simple modelling, the designers had felt that such a building was worthy of being monitored to assess whether the zero space heating target was realisable. The autonomous house was, after all, the only one of its type in the UK. A similar (energy only) government-funded house at the Fraunhofer Institute in Germany had cost some $13 million to construct, and received detailed monitoring. No scientific body could be found prepared to make the investment to monitor our autonomous house because, or so it seemed, a building designed by architects could not make good science.

As one peer reviewer commented, "What can be learned from one building?".

Real World Needs

The problem with being an architect, or someone who practices architecture, is that inevitably the end product exists in the real world and, as such, for all the reasons listed above, it tends to be seen as poor science. Equally, because as an architect one is interested in numbers, such buildings are often viewed by architectural critics as not real architecture, springing from performance parameters rather than from the soul.

However, difficult as it might seem, perhaps there is a need and a place for science conducted within the real world, and perhaps experiential learning is a justifiable basis on which to make decisions. Maybe it is sufficient to know that a certain building behaved in a certain way in a certain place. From this knowledge other such buildings may emerge, which in turn will produce certain results in certain conditions. This reiterative process will gradually refine knowledge until something emerges that begins to be the most appropriate way to do things in a particular location. This model is, after all, how craft knowledge or vernacular knowledge has been obtained.

In fact the autonomous house is being used to create a local vernacular in Nottinghamshire -- a group of five autonomous houses is now under construction, and the local council is now planning an autonomous village. These developments were the direct result of building the first house, which demonstrated that it was possible. Perhaps the scientific method is not the only way to advance knowledge about the world.

Brenda and Robert Vale are with the University of Auckland's Faculty of Architecture, Property and Planning.

Brenda is with the University of Auckland's Faculty of Architecture, Property and Planning.
Robert Vale is with the University of Auckland's Faculty of Architecture, Property and Planning.