The ultimate goal of building and construction – in relation to environmental issues – is to construct in an environmentally neutral way; or, as the Brundtland Report states, to consume in such a way that our children have the same choices that we have. Construction will always be needed, and will always consume resources. But in accordance with the conditions of the Brundtland Report, we should move construction into a direction that does not deplete resources, and does not worsen living circumstances through harmful indoor or outdoor environmental effects.
Improving our efficiency in resource consumption is the only way in which we will be able to continue our current way of life. Ernst Ulrich von Weizsäcker in particular has given meaning to this task by adding targets to this strategy. His book Factor Four has placed the issue at the forefront of the international agenda. It has been calculated that in order to (only) maintain the world average lifestyle a factor 4 of improvement in efficiency of resource consumption is necessary, based on global resource availability, effects on climate change, and coping with growing welfare for developing countries.
Measuring a factor x improvement heavily relates to the chosen benchmark. In the Netherlands we have reduced consumption from an average of 3.500 m3 natural gas for housing stock heating (1970s) to 1.700 m3, which is an improvement of factor 2 (for heating, not for the building). However, if we compare this 1.700 m3 against fuel consumption for the heating of a pre-1900s house, the result is higher energy consumption today. At that time only one room in the house was heated for just a few hours each day, while today the whole house is heated throughout the day, meaning that we have made improvements in terms of comfort, not in energy consumption. Therefore the setting of benchmarks is an important issue.
Building activities will always require some environmental load: the mere fact of living already implies use of earthbound resources, so it is generally not very efficient to calculate emissions and other effects in an absolute way. The ultimate target is not to avoid resource use at all, but to use only “reproductive resources” (“regrowable, renewable and replaceable”) to create a balanced situation. When this is achieved, we will still use resources, but usage will be sustainable: it can be maintained well into the future. The concept of Closing Resource Cycles lies at its basis (Rovers, 2007).
In developing an approach for assessing sustainable building, the Three Step Strategy (in the Netherlands named Trias Ecologica) has proven to be useful. The first step in this principle is to reduce the need or use of anything. The next step is to use renewable sources to supply the need. And if 1 and 2 are not sufficient to cover the activity, the third and final step must be applied, which is to supply the remaining need as efficiently as possible.
When adapted to energy, for instance, this leads to a significant reduction in demand (via insulation, efficient ventilation, daylight optimisation, etc.), the introduction of renewable energy (solar collectors, passive solar gains by design, solar electricity, etc.) and as last step: very efficient use of fossil fuels for any remaining need. These steps must be applied in that order. The same approach can be used for materials, water consumption, and even for maintenance or installations.
The natural progression of the Three Step Strategy approach leads to a closed cycle approach, where all needs are taken care of in steps 1 and 2, and step 3 is eliminated. At that point, non-renewable resources are no longer needed, and there will be a balanced situation for the activity. An approach of “adding measures” will not be sufficient to create this optimal situation: innovative and creative concepts are needed to accomplish this. Of course, this cannot be implemented in one day or one year, at least not on a wide scale. Nevertheless, the concept should be clear, and any choice to establish part of the concept should be made in a way that does not exclude realisation of the entire concept at a later stage.
When using the Three Step Strategy it is important not to combine the different performances (energy, materials, etc.) into one figure: there should be progress on all topics separately. This has led to measuring a building's performance by means of easy indicators, such as total mass and the percentage of renewable and recycled materials used. If this equals 100, the ideal situation has been achieved. This futuristic ideal aside, it is an easy and honest way to benchmark progress: in the Netherlands, the amount of renewable and recycled materials in an average house is around 8%. It is now easy to define a factor to improve the performance of the house, for example a factor of 4 (32%), to be realised either by reducing the mass and/or by increasing the amount of renewable and recycled materials used. The same can be done for other environmental issues.
This principle approach has been the basis for the ATLAS project: documenting houses and buildings along these indicators as a benchmark for future improvements. The initial study presented in this book was part of Wageningen University's ongoing ATLAS project. The study has documented Mexican housing according to this approach, using comparisons with similar studies of other countries' housing performance. It has shown to be an effective way to reveal main areas of improvement, and can be broadly applied to start analyses. In this research, Olivia Guerra Santín has extended the set of indicators to a more detailed level and has applied it to the case of Mexico, partly during her work at Delft University of Technology's OTB Research Institute.
Although we are still improving the approach, I hope this can act as an example for others to build on a global overview of documented housing, as is the intention of the ATLAS project.
Wageningen University, Urban Environmental Group