Building codes aren’t climate ready, but changes are coming

The world’s climate is changing more quickly than building codes are being updated, putting lives and structures at risk, according to panelists at the Building Innovation 2023 conference in Washington, D.C., last week. 

In fact, only about a third of the U.S. is covered by disaster-resistant codes, according to panelist Daniel Bass, an architect with the Federal Emergency Management Agency. Although climate risks interact with each other, building and zoning codes are not meshed accordingly and vary by locality. Wildfires, for example, must be addressed at a community and neighborhood level, since a fire at one building threatens all the structures around it.

This holistic thinking is vital because sometimes climate mitigation efforts conflict with each other. Bass gave an example from the 2021 Marshall Fire in Boulder, Colorado, where grass-filled drainage canals, built to deal with stormwater runoff, inadvertently created “fire superhighways” that spread flames directly into the hearts of towns and subdivisions.

For the most part, buildings in the U.S. are not designed for future conditions or even current climate change-fueled extreme weather, and growing flood and fire activity is forcing residential and commercial insurers to leave coastal states like California, Florida and Louisiana.

Plus, people increasingly live in high-risk areas — both because threats are growing and because people choose to build in and move to risky areas. For instance, at least 10% of the U.S. population lives in 500-year floodplains, according to NYU Furman Center, which now flood much more frequently than historically predicted. Wildfire threat is growing as well, including in areas once deemed low-risk.

As data and knowledge of these threats evolve, building codes and standards must as well, said panelist Chad Berginnis, executive director for the Association of State Floodplain Managers. For example, the National Flood Insurance Program minimum standards, the basis of flood codes across the country, have not been updated in 45 years, making it difficult to design truly resilient buildings. The U.S. also lacks consistent flood design standards for infrastructure, he said.

Another key issue is that building codes don’t address multiple extreme weather events, especially within a relatively short period of time, said panelist Paul Totten, building enclosures practice leader with Montreal-based contractor WSP. Building codes typically address resilience to a single disaster, not two or three in a year, which is an increasingly common pattern. 

Climate-aware codes in the works

More accurate codes and projections are coming. The newest edition of the ASCE 7, the most widely used professional standard guide used by engineers, for the first time includes a supplement that addresses how climate change is impacting flooding and sea level rise, according to panelist Dan Cox, professor of civil engineering at Oregon State University, who worked on the update. 

The new standard ties load standards to risk categories and now bases them around the 500-year floodplain rather than the 100-year benchmark. Structures with low impact to human life, such as parking garages, still use the old standard.

The ASCE/SEI 7-22 supplement also includes for the first time a flood-mitigation planning requirement relative to sea level rise over the service life of a structure. For now it’s based on historic rates of sea level rise, rather than projections that show this metric is likely to accelerate in coming decades, according to Cox.  

The guide also has first-ever criteria for tornado-resistant design, another form of extreme weather increasingly occurring outside historical boundaries. This new information is set to be included in the 2027 International Building Code update, and upcoming editions will have an entire new chapter for future conditions that address flooding, ice, wind and more.

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