Should Heat Be Legal

Asbestos advertisement, August 1917 Scribner's Magazine

By Keenan Gibbons

In the early 20th-century there was a groundbreaking new architectural material that took the world by storm. It was durable, waterproof, weatherproof, fire-resistant, highly non-conductive, and insulating. It could adhere to any surface, be made in any color, and was completely odorless. What was this miracle product? Asbestos.

Even today, a quarter-million people die from cancerous asbestos-related exposure every year despite heavy regulations. Imagine if it were unregulated?

There is a peculiar gap in the way we regulate the built environment. We have become very good at regulating things that we discover can hurt us in obvious and familiar ways.

Buildings must withstand certain structural loads. Roof assemblies must meet fire standards. Plumbing systems must protect drinking water. Sites must have requirements for managing stormwater. More recently, energy codes have begun to address how much energy buildings consume, and how efficiently they use it throughout the day.

Diurnal Variation of the Urban Heat Island-the city surface is nearly 20°F (11°C) warmer after sunset than before sunrise, Keenan Gibbons / SmithGroup

Therein lies the problem: heat does not fit neatly into any of these categories. Heat is partly a building problem but it does not stop at the building envelope. Heat is partly a landscape problem but it is not simply a matter of planting trees.

Heat is an infrastructure problem, a public health problem, an energy problem, and increasingly an economic problem. Most importantly, it is a problem that transcends property lines.

That makes heat difficult to regulate because our regulatory systems tend to be organized around the things we build, own, and permit - not necessarily the conditions those things create around them.

My previous three articles in this series have been an attempt to make that condition visible. We started by looking at how poorly conventional measures of heat describe what people actually experience. We then moved closer, to the scale of the sidewalk, where the relationship between material, shade, exposure, and human comfort becomes much harder to ignore. And then we considered the price of those decisions: the costs that accumulate when hot landscapes increase energy demand, constrain how people use public space, and place additional burdens on already vulnerable communities.

Once those connections are visible, policy becomes less abstract.

If a material can measurably increase heat exposure, should its use be entirely a matter of individual choice? If a development can make the surrounding public realm hotter, should that effect be considered during permitting? If shade, reflective surfaces, and vegetation can reduce thermal exposure, should they be treated as amenities or as infrastructure?

Atlanta recently offered one answer.

In June 2025, Atlanta adopted a Cool Roof Ordinance that amended its building code to establish solar reflectance requirements for roofs. The policy was supported by the Smart Surfaces Coalition and was subsequently amended in 2026 to adjust its effective date and provide additional compliance options. The requirements took effect in June 2026.

On one level, this is a very narrow intervention. It concerns roofs and the materials used to construct them, but that narrowness is precisely what makes it significant.

The Atlanta Cool Roof Ordinance / Smart Surfaces Coalition

The ordinance does not ask a developer to demonstrate that they are committed to climate adaptation or a property owner to participate in a voluntary sustainability program. It establishes a measurable characteristic of a built component and incorporates that characteristic into the process of construction and permitting.

In other words, heat has become a code issue.

That is an important transition because regulation is one of the few mechanisms we have for changing the cumulative effect of thousands of individual design decisions.

A single roof will not transform a city, nor will a single parking lot. But cities are made from thousands of roofs, parking lots, sidewalks, and streets - along with parks and plazas - each making a small contribution to the thermal environment.

The same logic applies to the landscape.

We would not expect a single stormwater facility to solve flooding across a watershed. We regulate individual sites because their cumulative effects matter. Heat deserves a similar way of thinking.

Minimum City of Detroit Drainage Charge achieved through a 35' x 300' rain garden, performing as designed for a 20+ year storm during a 5" rain event at the substantial completion punchlist walkthrough, Keenan Gibbons / SmithGroup

The difficulty is determining what exactly we should regulate.

A requirement for cool roofs is relatively straightforward because the performance of the material can be measured, but a sidewalk is different. Its thermal performance depends on orientation, surrounding buildings, paving, shade, vegetation, wind, and the time of day. A tree is not just a piece of landscape infrastructure. Its cooling value depends on where and how it is planted, whether it survives, and whether its canopy eventually reaches the people who need it.

This is where policy must catch up with the way heat actually works.

We do not necessarily need a code that dictates every material or prescribes a particular landscape. We need a framework capable of recognizing thermal performance as an outcome.

That could mean:

• Incorporating shade into site planning requirements.
• Evaluating the thermal consequences of extensive paved areas.
• Protecting existing canopy as seriously as we protect other forms of site infrastructure.
• Using surface reflectance, tree canopy, or thermal exposure as measurable criteria in development review.

And it could mean asking a different question during design. Not simply does this site comply? But what thermal environment will this site create?

There is an important federal counterpart to this local experimentation. The Excess Urban Heat Mitigation Act, reintroduced in 2025, would establish a $30 million grant program through the U.S. Department of Housing and Urban Development for projects addressing excess urban heat. Eligible strategies include cool roofs and pavements, green roofs, tree planting and maintenance, shade infrastructure, cooling centers, and public education.

The legislation is significant. While a grant program can't solve the problem by itself - especially not at $30 million (try $30 billion) - it formally recognizes something our fragmented approach to heat often obscures: heat mitigation requires both investment and regulation.

We need investment to cool the places that are already hot. We also need rules that keep us from continually producing more hot places. Those are different responsibilities.

A grant can help plant trees on an existing street. A public program can retrofit a schoolyard.

A code can make sure the next street is designed with shade in mind. A development standard can influence what the next schoolyard looks like.

Public investment addresses the accumulated legacy of past decisions. Regulations change the decisions being made now.

The policy challenge is determining where heat belongs within the systems that already govern how cities are built. That may ultimately be the most important shift.

We do not need a separate regulatory universe for heat. Heat can become part of building codes, landscape standards, street design, zoning, capital planning, public procurement, and development review. The pieces already exist. What is missing is the recognition that they are connected.

Atlanta's roof ordinance is useful because it demonstrates that this can begin with something tangible and measurable. The federal legislation is useful because it recognizes the need to invest in communities that cannot simply wait for new construction to solve an existing problem. Yet neither is the endpoint.

The next step is to move beyond the roof.

If heat happens at the scale of a sidewalk, then eventually the sidewalk has to become part of the conversation. So do the parking lot, the bus stop, the schoolyard, the plaza, the park, the street tree, and the open space between buildings.

Selden Courtyard Detroit with permeable pavement + moveable seating on tracks, Keenan Gibbons / SmithGroup

Every landscape does not need to look the same. But thermal performance should become one of the things we expect landscapes and buildings to perform.

For a long time, heat was treated as something that happened to cities, but we now understand that cities also make heat. We can measure that heat. We can identify its material causes and calculate its costs. We now know how to design differently.

The lingering question is whether we are willing to make those choices part of the rules by which we build. Because regulation is ultimately a reflection of what we have decided is important enough to require.

We have already decided buildings should not collapse, stormwater should be managed, fires should be contained, and cancer-causing materials should be regulated.

Does keeping people cool enough to safely inhabit the places we design belong on that same list?

Keenan Gibbons, ASLA, PLA, LEED GA, is ASLA's Climate & Biodiversity Action Fellow for 2026-2027. He is principal and director of landscape architecture at SmithGroup and lecturer at the University of Michigan.