What role will the ZEB definition have in the future? Experience has shown that a well-defined goal for the environmental ambition is crucial for the success of zero emission building projects.
Due to different boundary conditions, it may be difficult to achieve a full life cycle ZEB for all buildings. For example, reaching a high ambition level may be less challenging for small buildings such as single-family residential buildings, because the areas available for energy generation (e.g. solar modules) per heated floor area are larger than in more compact high- rise commercial buildings. Moreover, local climate conditions and contextual boundaries such as urban density may limit the possibilities of reaching a full Zero Emission Building. The Norwegian ZEB Centre has therefore developed a hierarchy of ambition levels for zero emission buildings, to allow flexibility for different types of buildings and local boundary conditions. The defintions include detailed descriptions of a number of criteria such as system boundaries and calculation procedures, and it addresses all the life cycle stages as defined in EN 15978 on Sustainability of construction works.
The main ambition levels applied by the ZEB Centre are described as follows, starting with the lowest level:
ZEB-O÷EQ: Emissions related to all energy use for operation “O”, except energy use for appliances/equipment (EQ), should be compensated for with renewable energy generation.
ZEB-O: Emissions related to all operational energy “O” should be compensated for with renewable energy generation.
ZEB-OM: Emissions related to all operational energy “O” plus embodied emissions from materials “M” should be compensated for with renewable energy generation.
These ambition levels have all been applied and tested in the nine Norwegian pilot building projects described in research section in this report. The ZEB Defintion also includes two higher ambition levels (ZEB-COME and ZEB-COMPLETE1), but these levels have so far not been applied in any building projects in Norway.
Experience from the pilot building projects suggests that it is possible to reach the lowest ambition level for most new building projects with little extra cost, and that this can potentially yield a positive cost-benefit ratio in a life cycle perspective.
As the building industry gains experience with such buildings and the market gains from the economic benefits of scale, costs will decrease. There have already been dramatic falls in the cost of PV, and other technologies are gradually becoming less expensive as they develop. In addition, there are potential benefits of high-performance ZEBs which have not been taken into account in traditional LCC (life cycle cost) analyses, such as higher renting values, higher residual values, and productivity values.
In the next revision of the NORWEGIAN building regulations (TEK20), the ZEB-O÷EQ ambition level could well be implemented since it fits well with the EU requirement of “nearly zero energy buildings”. However, since the analyses of the ZEB pilot buildings show that emissions from production of materials may constitute about 50% of total life cycle emissions, it is strongly advised that some requirements with respect to materials be included in the future building codes. In order to simplify the procedure, this could be enforced through a requirement to document parts of the building structure. The calculation methodology has already been developed in ZEB and can be used as a basis for the documentation procedure.
The higher ZEB ambition levels can provide a basis for additional future regulations, as well as being useful for current developers and governmental institutions that want to be frontrunners and to promote buildings that contribute to a low carbon society.