Human beings can remain healthy and active only within certain bounded temperature ranges. Though individuals and cultures have historically been able to adapt to Earth’s wide climatic variety, there are limits to these adaptations, and knowable consequences when those limits are exceeded. Expanding research on the causes, forms, and complications of thermal extremes in the Anthropocene era supports a recognition of extreme heat events as a clear and present danger to human health and well-being. Extreme Heat: Hot Cities – Adapting to a Hotter World, organized by the Design for Risk and Reconstruction Committee (DfRR) of the American Institute of Architects New York, marks a convergence of disciplines that focus on heat waves as a health hazard, at both local and global scales. As the program’s November 2015 symposium underscored, heat waves are increasing as the climate changes, yet they are remediable through adjustments in the built environment and its associated social systems.
The urban heat island effect exacerbates global-scale rises in temperature, and local heat waves are increasing in both severity and frequency. Particularly in urban hardscape environments, where populations face other sources of vulnerability involving access to cooling, mobility, medical care, and social, cultural, and economic resources, heat waves have become an early and critical front in the struggle against deleterious climate-change effects. Architects, planners, engineers, public officials, scientists, scholars, and the business sector are accordingly developing strategies that pursue the nonexclusive aims of climate adaptation and mitigation in urban settings. Together, these endeavors constitute a distinct domain of knowledge and practice: urban heat management.
This field builds on best practices that are already in place within healthy communities. Leaders in the architectural, engineering, and construction (AEC) industries recognize that a stable community engages a triad of sustainability: it is resilient socially, economically, and ecologically. Some other industries have yet to accept these goals fully, and AEC professionals have a responsibility and opportunity to advocate for policies that elevate the sustainable standards of the built environment. The benefits from these practices are not limited to improved temperature ranges in our cities; they extend to the entire planet.
Historically, there has been resistance to investing in climate change adaptation on the grounds that it would divert resources supporting mitigation. Adapting to higher global temperatures, some hold, would be a capitulation to interests that are implicated in greenhouse gas emissions, or to a cynical fatalism about humanity’s future, or both. However, the experts that assembled at the Extreme Heat symposium reject the zero-sum assumption that the relation between adaptation and mitigation is fundamentally adversarial. Instead, taking a term from speaker Brian Stone, the two integrate through adaptive mitigation. This strategy recognizes that both components are imperative and that action on both fronts can be mutually reinforcing.
As a strategy, adaptive mitigation recognizes that climate change adaptation and mitigation are both imperative and that action on both fronts can be mutually reinforcing.
Adaptive mitigation comprises many interventions that advance multiple aims. Such aims include reforestation and regreening of urban environments (cooling local sites through evapotranspiration and shading while improving carbon balance and air quality), compact transit-oriented development (reducing both automotive greenhouse gas emissions and waste heat), and coverage of heat-absorbing infrastructure, such as parking lots, with photovoltaic panels (reducing heat concentration in asphalt by shading while providing renewable energy). The design, engineering, and planning professions, symposium speakers contend, have the opportunity to generate win-win scenarios that address these aims and amplify incentives for their expansion.
Health Priorities and the Climate-Science Consensus
For urban dwellers, local heat waves bring global-scale rises in temperature close to home, and they do not spare disbelievers in such phenomena. The hottest year in which global temperatures have ever been recorded was 2015, according to National Oceanic and Atmospheric Administration (NOAA) data. With the exception of 1998, a strong El Niño year like 2015 that is tied for sixth hottest, 15 of Earth’s 16 warmest years on record occurred in the 21st century. Heat waves are not just inconvenient but deadly, and their increasing hazards call for purposeful, scientifically guided action by all relevant professional sectors. Even skeptics of the data can recognize the health risks associated with extreme heat, and acknowledge the importance of engaging in adaptive mitigation.
Expanded awareness of acute heat stroke and heat- exacerbated chronic disorders is no longer the exclusive province of medical personnel, but a matter for design, engineering, and planning professionals to consider in their creation of healthy, sustainable communities. Detailed studies of individual heat waves and their geographic vulnerability patterns shows correlations between the distribution of community resources and rates of morbidity and mortality in heat-affected neighborhoods. These correlations underscore the importance of proactively bolstering and restoring societal safety nets wherever they are in disrepair. Human health corresponds with the built environment, and its promotion is inseparable from environmental justice.
Human health corresponds with the built environment, and its promotion is inseparable from environmental justice.
This correlation, often most tangibly experienced through medical and humanitarian frameworks in the context of heat island-related hazards, is not always enough to spur action. In order to override political paralysis and overcome disinformation in the marshaling of public perceptions about climate-related risks, we need to gather more data and share it more compellingly. The research to date points promisingly toward adaptive and mitigating strategies that are achievable with known technologies. Other measures require further detailed data (e.g., on intermediate-range climate projections, the granular thermal changes effected by urban reforestation, or the relative benefits of green and cool roofs in different settings), and all commentators support expansion and refinement of the knowledge base. Viewing health- oriented data as an essential signal and climate politics as noise, one of the clearest recommendations throughout the symposium is the need for a higher signal-to-noise ratio in the growing discourse about climate and heat.
Viewing health-oriented data as an essential signal and climate politics as noise, one of the clearest recommendations throughout the symposium is the need for a higher signal-to-noise ratio.
Biomimetic and Neotechnic Design
Organisms have been able to adapt to hot ecological niches for much longer than humans have been deploying mechanisms toward similar ends. Inspired by this ability, many design professionals study nature’s methods of conserving and employing water, using shade and circadian rhythms, managing energy transfer, and maximizing the efficiency of forms. The resulting biomimetic strategies characterize many advanced buildings and materials, which are achieving high energy-conservation performance in even the hottest of sites. Of the AEC industries’ biomimetic advancements, especially notable are: the attainment of net-zero energy input/output balance in both new construction and retrofits; the use of solar heat gain to (paradoxically) cool a building; the potential of photovoltaic panels to power condensation and irrigation systems that then transform desert sites into agricultural production centers; and the role of selected plant species in assisting with graywater treatment and thermal management when integrated into building systems.
Alongside the use of natural models and natural building components, strategies for heat management draw from the formal vocabularies of indigenous architectural traditions in hot regions. Aided by contemporary parametric design tools, design professionals are crafting site-specific forms that use prevailing winds and internal airflow patterns to passively augment cooling. The era dominated by sealed building envelopes, pervasive impervious hardscapes, standardized industrial materials, and profligate use of fossil-fuel-powered mechanical ventilation can and should end. Instead, we have the opportunity to embrace a range of time-tested and nature-tested systems based on thermal mass, shading, strategic lighting, insulation, and hydrology, all coordinated through sensors and information technology. A more adaptive approach to thermal control can be a powerful driver of the comprehensive transition from paleotechnics to neotechnics, drawing on the most enduring strategies of eotechnics (to borrow the terminology of Lewis Mumford), in design, engineering, and construction.
Complexity and Interdependencies
Extreme heat calls for situationally-specific approaches that are informed by both short- and long-term considerations, and that fully weigh the nuanced implications of the approach. One conundrum recognized by several symposium speakers is that mechanical air conditioning, the most immediate form of relief during an acute heat wave, also contributes to waste heat and energy consumption. Outside of the rare settings where renewable energy sources are dominant, mechanical air conditioning also contributes to greenhouse gas emissions. Similarly, green (vegetated), cool (white or silver), and blue (water-capturing) roofs may constitute low-hanging fruit for cities seeking cost-effective ways to increase urban albedo. However, some preliminary observations suggest that the resulting temperature differentials are conducive to underside moisture condensation, or that the light reflected off a roof may still result in a warmer atmosphere, among other concerns. Urban density is often cited as a positive counterforce against climate change, since denser habitats amplify efficiencies in transportation, winter heating, and other energy-using, carbon-generating activities. Yet urban environments maximize vulnerability to heat hazards, as evidenced in the 1995 Chicago heat wave, the 2003 European heat wave, the thermal aspects of Hurricane Katrina in 2005, and other high-mortality events. As New York City experienced during Hurricane Sandy, interdependent infrastructure systems, such as electrical grids and transportation, can be very vulnerable to cascades of failure.
These illustrations of complexity and interdependency imply that truly interdisciplinary work has critical, concrete value in this field. That so many symposium participants call for collaboration among professions is neither an accident nor an automatism, but a purposeful collective recognition that heat management is not a category of problem for which any single magic-bullet solution can suffice.
Incrementalism and Catastrophes
The “frog in boiling water” story, famously recounted by Al Gore in An Inconvenient Truth, continues to have important metaphoric power. While herpetologists have pointed out that frogs do not actually remain in water as it warms, the story poignantly conveys the different responses evoked by a gradual change and a sudden shock. In the context of the current state of urban heat management, these responses manifest as abstract recognition of hazards requiring an eventual response and shock-hardened actions that are immediate, drastic, and disruptive.
Preparation and resilience, as articulated by the symposium speakers and regularly by DfRR leadership, call for a steady acceleration in these conceptual negotiations between gradual and emergency responses. Urban catastrophes such as Hurricane Sandy reveal the weaknesses in infrastructural and social systems, while generating (if only momentarily) public and political support for investments that prevent or mitigate a recurrence of similar events. It is essential to reinforce and extend these periods of recognition and resolution beyond the immediate aftermath of a catastrophe, so that public attention does not erode and the political will to marshal resources constructively is preserved.
It is essential to extend these periods of recognition and resolution beyond the immediate aftermath of a catastrophe.
Heat as Potential Asset
There may be an optimistic way of viewing the immense amount of excess heat in today’s urban environments, as emphasized by Anna Dyson and Chris Benedict, among other symposium speakers. By recognizing heat as a form of energy that can be redirected rather than wasted, a range of heat-recapture technologies offers the possibility of improving on currently dominant energy technologies in both performance and sustainability. Such technologies can be found in the energy-recovery ventilators of Passive House buildings, in the recirculating systems of integrated capillary-tube façade panels, and in high-efficiency solar heat collectors.
The benefits of heat-conscious design at the single-building scale will aggregate, impacting neighborhood, municipal, and regional scales.
As advances in material science and green chemistry enable greater thermal efficiency on the single-building scale, the benefits of heat-conscious design will aggregate to impact neighborhood, municipal, and regional scales, and beyond. To successfully make heat an asset in a single building project is to move us one step closer to harnessing heat’s positive impacts globally. In addition to embracing the urgency of hazard remediation, urban heat management involves recognizing long-range opportunities to re-engineer the built environment in ways that conserve, apply, and honor the gifts of the sun and the Earth.
Implications for Advocacy and Action
Extreme heat events are becoming more frequent, making it critical for architects, planners, engineers, public officials, scientists, scholars, and the business sector to mobilize. The varieties of evidence and discourse offered at this symposium point to the following forms of action:
Design should support the capacity of a building or infrastructural project to manage critical resources (thermal and electrical energy, air, water, information) more efficiently and in ways more conducive to health. Design should draw from the full range of available strategies, from traditional/vernacular forms that use shading, orientation, passive ventilation, and thermal massing, to more contemporary technologies and materials, such as photovoltaics, hydrologic innovations, green chemistry, waste-heat recovery/reuse and other Passive House techniques, and biophilic/biomimetic principles. In this arena, architects have the opportunity to take leadership roles both in preliminary design phases and in post-occupancy phases.
Building codes should enforce and encourage sustainable, resilient, and thermally protective standards. Specific areas to be addressed include energy management (including renewable sourcing and net-zero energy input/output balancing), cool roofs, cool pavements, vegetative canopy cover and other shading strategies, access to energy-efficient air conditioning, air quality, maximum indoor temperatures, graywater reuse, and other thermally relevant variables. Changes in code
should incorporate best practices based on the most reliable contemporary research and incentivize continued research and elevation of standards.
Policies at the community, regional, and national scales should foster steady-state sustainability, mitigation of heat island effect, and acute event resilience in social, economic, and environmental manners. Top priority topics include: access to emergency cooling centers, medical preparedness, public education and outreach about heat-related hazards; appropriate urban densification; energy-efficient transportation, natural disaster or blackout preparation and response, inter-agency and inter-city coordination, social cohesion, behavioral/cultural adaptations, equitable services and attention to the needs of highly vulnerable populations, reforestation and urban regreening, ecosystem restoration, and regionally specific biodiversity management. Policy should also encourage and enforce ongoing research into the thermal, public health, and climatic effects of all relevant practices by the AEC industries, public and private entities responsible for infrastructure, and other social sectors.