Energy or carbon? Exploring the relative size of universal zero carbon and zero energy design spaces

One aim of zero carbon, or zero energy, buildings is to help slow climate change. However, regulatory definitions frequently miss substantial emissions, for example ones associated with the materials the building is constructed from, thereby compromising this goal. Unfortunately, including such emissions might restrict the design space, reduce architectural freedom or greatly increase costs. This work presents a new framework for examining the problem. The zero carbon/energy design and regulatory space forms a sub-space of the hyper-volume enclosing all possible designs and regulatory frameworks. A new mathematical/software environment was developed which allows the size and shape of this sub-space to be investigated for the first time. Twenty-four million building design/regulatory standard combinations were modelled and assessed using a tree classification approach. It was found that a worldwide zero standard that includes embodied emissions is possible and is easier to achieve if a carbon rather than an energy metric is adopted, with the design space twice the size for a carbon metric. This result is important for the development of more encompassing regulations, and the novel methods developed applicable to other aspects of construction controlled by regulation where there is the desire to examine the impact of new regulations prior to legislation.

Practical application: As energy standards become more strict, and given the growth in non-regulatory standards (such as Passivhaus), there is the need to study the potential impact of any element of a standard on the range of designs that can be built or the materials that can be used. This work sets out a general framework and method for doing this. The approach and results will be of interest to policy makers, but also to engineers and architects wondering what the key constraints to design the adoption of various philosophies to low energy/carbon standards might have within their work. For example, the implications of the building standard (or client) requiring embodied emissions to be included or the energy balance period for renewable generation to be monthly, not annual.