Past development of environmental performance assessment

(1) Stage 1
The oldest form of environmental assessment of buildings in Japan is the performance assessment of building environments, mainly indoor environments, which is basically aimed at improving living amenities or enhancing convenience for occupants. This can be thought of as Stage 1 in the evolution of the environmental assessment of buildings. At this stage, since the local environment surrounding the building concerned and the global environment were generally considered as open systems, environmental assessments paid no attention to the fact that buildings simply discharged their environmental loadings into their surroundings. In this sense, the philosophy behind environmental assessments was very clear, but opposite to today’s approach.

(2) Stage 2
The growth of public concern over air pollution problems or the effects of wind on pedestrians etc. in urban areas such as Tokyo in the 1960s led to the establishment of environmental impact assessments. This was the time when the concept of environmental loadings was initiated and incorporated into building environmental assessments, and this is thought of as Stage 2. Here, only the negative effects that buildings have on their surrounding environments, such as urban air pollution, wind damage, and daylight obstruction etc., are considered as environmental impacts, i.e. environmental loads. In Stage 1, the environment usually suggests a private space or property, whereas in Stage 2 it is a public (or non-private) space.

(3) Stage 3
Stage 3 in the evolution of the environmental assessment of buildings began after the increase in the consciousness of global environmental problems in the 1990's. A number of specific methods have already been proposed, based on extensive research experience, including BREEAM, LEED^TM and GB Tool. In recent years, building environmental performance assessment methods such as these have spread rapidly in society, particularly in developed countries, and they have also come to be used for "Design for Environment" and building environmental labeling (rating). The main issue in assessment at this stage is the negative impacts; in other words, the environmental loadings that the buildings have on the environment. That is to say, it considers Life Cycle Assessment (LCA), evaluating the environmental loads of a building throughout its life. In addition, building performance was also included as an object in some assessments, as in Stage 1. Notably, none of the above assessment tools clearly distinguish between these two basic assessment objects (in Stage 1 and Stage 2). Also, the scope (or boundary) of the assessment objects is not clearly stated. In this sense, the concept of environmental assessment in Stage 3 lacks the clear underlying philosophy found in Stage 1 and Stage 2, while the framework of assessment has expanded in Stage 3. The assessment framework, relative to the first and second stages, but conversely, the framework of assumptions on which the environmental performance evaluation is based has become unclear.

New Stage in the Environmental Assessment of Buildings

Development of CASBEE started from perception that the above situation required a reconstruction of the current environmental performance assessment framework into a new system clearly based on the perspective of sustainability. Stage 3 in environmental assessment began when it was recognized that the capacities of local environments, and the world as a whole, were reaching a limit. As a result, the concept of closed ecosystems became essential for determining environmental capacities when conducting environmental assessments. Therefore a hypothetical enclosed space bounded by the borders of the building site, as shown in Figure 1, is proposed here in making environmental assessments of buildings. The on-site space bounded by these hypothetical boundaries can be controlled by the parties involved in the building, including the owner and planner, but the space beyond is public (non-private) space, which is largely beyond control.
The environmental loads can thus be defined as "the negative environmental impact that extends outside to the public environment beyond the hypothetical enclosed space." The improvement of environmental performance within the hypothetical enclosed space is defined as "the improvement in living amenities for building users." Dealing with both factors, the stage 4 environmental assessment clearly defines these two factors, and distinguishes one from the other as defined by BEE. This makes the philosophy of assessment at stage 4 much clearer, and it has been used to form the framework for CASBEE, and it is the basis of the CASBEE framework.

Figure 3. Hypothetical enclosed space divided by the site boundary

From Eco-efficiency to Built Environment Efficiency (BEE)

The concept of Eco-efficiency has been introduced for CASBEE to enable the integrated assessment of two factors, inside and outside the building site. Eco-Efficiency is normally defined as "Value of products and services per unit environmental load. Efficiency is commonly defined in terms of input and output quantities, so a new model can be proposed for an expanded definition of Eco-Efficiency, as "(beneficial output) / (input + non-beneficial output)." As Figure 4 shows, this new model of environment efficiency can be extended to define Built Environment Efficiency (BEE), which CASBEE uses as its assessment indicator.

Figure 4. Development from the Eco-efficiency concept to BEE