For Survivors of Natural Disasters, Green Rebuilds Bring Silver Linings

Mitch, a 72-year-old retired financial planner, bought his Houston home in 1987 and has seen it flood six times since then. A trio of particularly harsh storms destroyed family photos, his 50-year-old vinyl record collection and the structural guts of the house itself, forcing him and his wife into a rental apartment for three years.

His neighbors faced similar destruction. Across nearby blocks, “they’re building all these new homes,” said Mitch, who asked that his last name be withheld for privacy reasons.

Few Southern cities suffer the region’s double whammy of increasingly severe storms and overtaxed energy grids more than Houston. The storm that delivered the final blow to his house was 2017’s Hurricane Harvey, which destroyed or damaged more than 200,000 other homes as well. In addition, a recent survey found that over two-thirds of Houstonians worry about losing electricity—and air conditioning—for more than a day in their steamy corner of Texas. 

To address those twin threats, University of Maryland researchers designed a simulator to predict storm damage and energy demands over the next 56 years in Houston’s Harris County, and discovered the advantages of “building back greener.” If victims of natural disasters rebuild their homes with an emphasis on sustainability, not only would electric grids get a reprieve, but the long-term economic benefits would significantly outweigh short-term costs—both for individual homeowners and county taxpayers as a whole.

Despite that promise, most survivors of natural disasters rebuild in energy-inefficient ways, largely out of urgency, familiarity, cost constraints or weak emergency provisions enacted by local governments, according to the researchers. To speed construction following this year’s devastating wildfires in Los Angeles, for example, California suspended popular conservation regulations.

When Mitch finally rebuilt his home, sustainability was not a priority, he acknowledged. “It’s more of, you just want to get back in here as soon as possible,” he said.

Rather than putting the onus solely on survivors to choose eco-friendly rebuilds, “stronger municipal policies would lead to huge potential savings for residents and the building stock,” said Linda Waters, a sixth-year Ph.D. student in civil and environmental engineering and lead author of a study published last month in Energy and Buildings and funded partially by the National Science Foundation and the Department of Energy.

Considering that local governments receive Federal Emergency Management Agency funding in the aftermath of hurricanes and floods, Waters said rebuilding policy could be shaped to essentially tell homeowners, "Here’s the money, but instead of buying a gas furnace, buy an electric heat pump for your home.”

To gauge county-wide savings, the researchers compared energy-efficient rebuilding to other green strategies. In one finding, they determined that if Harris County offered $1,000 subsidies to stimulate eco-friendly home construction, the net cost would be $240 for every ton of carbon saved. Meanwhile, similar subsidies supporting electric vehicle uptake are estimated to cost $2,350 per ton.

“For green rebuilds, the juice is worth the squeeze,” said Waters.

The economic benefits complement substantial environmental gains. In the best-case scenario, green reconstruction in greater Houston would cut projected energy consumption by 2.9%, drop carbon emissions by 3.6% and reduce the county’s peak electric load by 2.2% by 2080, the study found. The calculations assume a continued groundswell of migration to Harris County, which added more residents last year than any other U.S. county.

To build her prediction simulator, Waters tapped a federal database that separates Harris County’s 1.8 million homes into 7,000 archetypes—based on variables including square footage, wall thickness and window size—and measured each model’s average energy consumption. To project storm damage, she combed through county tax assessment records and plotted each home on a map, then overlapped that information with the archetype data to create a new set of numbers, aided by an algorithm she designed.

Next, Waters’ team asked the simulator to consider a wide range of temperature fluctuations, population increases and flood frequencies in Harris County over 50 years, randomized by a UMD supercomputer. The researchers also borrowed from decision-making science to consider attitudes of average homeowners facing emergencies. Ultimately the simulator assessed 100,000 potential scenarios to generate a statistically reliable forecast.   

“Linda has done something really impressive by taking elements of many domains—from decision science, building technology, climate change and hazard modeling—and integrating them into a single model to generate findings,” said Allison Reilly, associate professor of civil and engineering and co-author of the study, which also includes fourth-year Ph.D. student Diako Abbasi and researchers with the University of North Carolina and Georgetown University. 

While the numbers are dizzying, the basics of green rebuilds are not. Common tactics include swapping gas water heaters for electric heat pumps, installing triple-pane windows and installing energy-efficient refrigerators, dishwashers and dryers. 

Though green upgrades can be pricier upfront, they cost less to run and are cheaper to install during post-disaster reconstruction than later on, the researchers noted. Installing an EV outlet in a garage during construction costs $10, while post-construction installation can run up to $500. A similar principle holds for solar panels.

The residential building sector accounts for 20% of energy consumption and 22% of carbon dioxide emissions in the United States—rates that are expected to increase as larger homes rise in the exurbs—but until U.S. policy catches up with the economics of eco rebuilds, American cities from Houston to Los Angeles will continue to miss opportunities to transform energy consumption in the face of increasingly unavoidable weather disasters, Waters said.

“If you’re going to rebuild you might as well rebuild sustainably,” she said. “It’s a promising way to kill two birds with one stone.”

As he rebuilt his home, Mitch chose a more energy-efficient air-conditioning system—not for environmental purposes, but to save on utility bills and raise his property value. Looking back, though, he acknowledges the sustainability benefits. 

“It’s hotter than hell in Texas,” he said. “With all these people moving here, we just don’t have the power to sustain the heat in the winter and the A/C in the summer, so the less I use, the better it could be for the grid.”