Two Categories of Assessment: Q and L

Under CASBEE there are two spaces, internal and external, divided by the hypothetical boundary, which is defined by the site boundary and other elements, with two factors related to the two spaces. Thus we have put forward CASBEE in which the "negative aspects of environmental impact which go beyond the hypothetical enclosed space to the outside (the public property)" and "improving living amenity for the building users" are considered side by side. Under CASBEE, these two factors are defined below as Q and L, the main assessment categories, and evaluated separately.

Q (Quality): Building Environmental Quality & Performance:
Evaluates "improvement in living amenity for the building users, within the hypothetical enclosed space (the private property)."

L (Loadings): Building Environmental Loadings:
Evaluates "negative aspects of environmental impact which go beyond the hypothetical enclosed space to the outside (the public property)."

Four Target Fields of CASBEE and Its Rearrangement

CASBEE covers the following four assessment fields: (1) Energy efficiency (2) Resource efficiency (3) Local environment (4) Indoor environment These four fields are largely the same as the target fields for the existing assessment tools described above in Japan and abroad, but they do not necessarily represent the same concepts, so it is difficult to deal with them on the same basis.

Therefore the assessment categories contained within these four fields had to be examined and reorganized. As a result, the assessment categories were classified as shown in Figure 5 into BEE numerator Q (Building environmental quality and performance) and BEE denominator L (Reduction of building environmental loadings). Q is further divided into three items for assessment: Q1 Indoor environment, Q2 Quality of services and Q3 Outdoor environment on site. Similarly, L is divided into L1 Energy, L2 Resources & Materials and L3 Off-site Environment.

Figure 5 Classification and rearrangement of assessment items into
Q (Building environmental quality and performance) and L (Building environmental loadings)

Environmental Labeling Using Building Environmental Efficiency (BEE)

As explained above, BEE (Building Environmental Efficiency), using Q and L as the two assessment categories, is the core concept of CASBEE. BEE, as used here, is an indicator calculated from Q (building environmental quality and performance) as the numerator and L (building environmental loadings) as the denominator.

The use of BEE enabled simpler and clearer presentation of building environmental performance assessment results. BEE values are represented on the graph by plotting L on the x axis and Q on the y axis. The BEE value assessment result is expressed as the gradient of the straight line passing through the origin (0,0). The higher the Q value and the lower the L value, the steeper the gradient and the more sustainable the building is. Using this approach, it becomes possible to graphically present the results of building environmental assessments using areas bounded by these gradients (Eco-labeling). The figure shows how the assessment results for buildings can be labeled on a diagram as class C (poor), class B^-, class B⁺, class A, and class S (excellent), in order of increasing BEE value.

Figure 6 Environmental Labeling Based on Building Environmental Efficiency (BEE)