Environmental issues, costs, and limited energy supply, among other concerns have been driving the efforts toward more energy efficient buildings over the last four decades. Hence, energy efficiency is not only well-established within the building design and construction industries, but is also an active field of research. Many countries have state-mandated building energy codes that are becoming more stringent with time. Therefore, the building stock in many regions is becoming more efficient. With the observed increase in frequency and intensity of hot weather events in urban areas around the world and research that suggests a more extreme future, the resiliency of the built environment to heat has become a major concern for planners and policymakers. Therefore, it is important to understand how the evolution of energy codes affects the resiliency of buildings to heat.

In this study, the authors used whole-building energy simulations to investigate the performance of high-rise residential apartment buildings under a three-day power outage scenario coinciding with a three-day heat wave. The authors modeled buildings compliant with consecutive versions of two building energy codes and standards commonly used in the U.S. to investigate the effect of building code on resiliency in all distinct climate zones within the country. The results suggest that in most climates, indoor conditions exceed critical thresholds during the modeled scenario. Moreover, the authors observed a synergy between energy efficiency and resiliency to heat in warmer climates. However, in heating-dominated climates, newer codes can potentially have an adverse effect on heat resiliency of buildings.

In general, building codes in heating-dominated climates moved towards less resiliency to hot summer conditions. In contrast, the passive performance of buildings in cooling-dominated climates improved as the codes evolved. The authors' investigation into contributing factors suggests that this is mainly due to added insulation and air-tightness with no regard for strategies that could avoid overheating. This could be an important consideration for entities generating building energy codes and standards. Hence, understanding how various aspect of a building design can affect resiliency to heat is of vital importance. While better envelope insulation—an important strategy to reduce energy consumption and carbon emissions—should still be advocated in newer codes, other strategies that benefit both cooling and heating energy demands such as thermal mass, proper shading, ventilation, and high albedo roofs should also be considered to avoid possible increases in overheating risks.