From Energy to Carbon It is time for a more robust and holistic measure of a building’s climate impact. SHRESTH NAGPAL AND RUSHIL DESAI
The traditional metrics of reductions in site energy, source energy, and energy costs - that have served as benchmarks for high performance buildings for decades – no longer provide a comprehensive picture of a building’s true environmental impact. Greenhouse gas emissions intensity (GHGI) associated with building energy use is, given what we know1, the pertinent metric to quantify building operational performance. In fact, many local jurisdictions and institutions now identify the importance of reducing a building’s GHGI and are beginning to incorporate this into their programs and legislation. New York City’s Local Law 972 passed in 2019 aims to achieve a 40% reduction in GHG emissions from 2005 levels by 2030 and 80% by 2050, through absolute GHGI targets for buildings. Similarly, City of Berkeley’s Climate Action Plan3 aims to achieve a 33% reduction from 2000 levels by 2020 and 80% by 2050.
Shreshth Nagpal Principal at Elementa Engineering, New York, NY Shreshth’s professional focus over the past fifteen years has been to understand and model building performance that results from the interaction between envelope configuration, climatic context, functional requirements, conditioning systems, and occupant behavior.
The first step towards decarbonization is designing buildings that successfully respond to the constraints and opportunities of the local climate, passively maximize occupant comfort, eliminate energy waste through user engagement and controls, and incorporate high-efficiency energy systems to meet the demand remaining after passive design and load reduction strategies. The second step is designing all-electric buildings. Since electricity is the only energy source that can realistically be completely carbon-free, electrification is the only credible path towards meaningful decarbonization of the built environment. When full electrification is not feasible at present, it is imperative to plan a transition away from all on-site fossil fuel consumption in a building’s design. The intent of this paper is to build upon these two widely recognized premises and focus on the third - relatively unexplored and poorly understood - strategy of demand management and load shifting of grid-purchased electricity. This paper will show that not only can load-shifting avoid significant grid emissions already, it can allow for a building’s GHGI to drop sharply even when it consumes a non-trivial amount of energy. This becomes especially relevant as the future grid gets cleaner. It is time we moved past building energy metrics, it is time we focused on Avoided Emissions as a building performance metric and a more robust and holistic measure of a building’s climate impact.
Rushil Desai Building Performance Analyst at Elementa Engineering, New York, NY Rushil is a specialist in ‘Net Zero Energy’ buildings, electrification and decarbonization, building to grid interoperability, and urban scale energy modeling.
