TUCSON — For the past 23 years, Jim Filipiak, 73, has lived in a 1976 singlewide mobile home. Mobile homes dominate the flat landscape of his Tucson neighborhood, a mostly treeless plot near the railroad tracks and Interstate 10. The retiree and Vietnam veteran has remodeled his home and kept up with maintenance, but there’s little he can do to shield himself from what has become the norm in Arizona: searing, deadly summer heat.

Filipiak has two window air-conditioners, but they suck up electricity and drive up the bill, so he only runs the AC for the few hottest hours of the day to protect his two rescue dogs. Even if he could afford a more efficient central AC unit, the wiring in his home couldn’t sustain it. Instead, Filipiak relies on an evaporative cooler, until summer rains and humidity in July and August render it useless. Then he relies on fans. In mid-June, when Tucson and Phoenix both broke records for triple-digit heat, the interior temperature of his home never dropped below 90 degrees, day or night.

Last summer’s relentless, 100-degree heat and compounding drought killed a record 520 people in Arizona — twice the total deaths reported nationally from hurricanes, wildfires, tornadoes, severe storms and floods, and a significant increase from the past decade, when heat-related deaths in Arizona never went above 283. With this summer already dangerously hot, researchers are sounding the alarm about a heat-vulnerable community that has been historically disregarded because of where they live: substandard, aged mobile homes.

Heat death investigations from 2020 are still pending, but at least 13 people in Maricopa County alone died in their mobile homes, said Patricia Solis, a geographer and executive director of the Knowledge Exchange for Resilience at Arizona State University. (Mobile home-specific death totals are not available statewide.) Thousands more are vulnerable again this summer, as punishing temperatures are already smothering parts of the country.

Already the first victims of natural disasters, residents of these older mobile homes are a microcosm of the at-risk population for heat emergencies: the poor and those living on fixed incomes, the very young and the elderly, people with disabilities, people who live alone and people of color. Filipiak’s neighborhood includes a Native American community.

“We are beginning to see this to be a real health concern, certainly a moral one,” said Margaret Wilder, with the School of Latin American Studies and the School of Geography, Development & the Environment at the University of Arizona. “It should be of concern to any policymaker.”

Wilder and Solis are members of the team of researchers, already well-versed in heat- and climate-related studies, who are collaborating on a project led by Mark Kear, assistant professor in the School of Geography, Development & the Environment at the University of Arizona. It began in 2019; their report will be published this fall.

“We are all exposed to global warming; the temperatures outside are up for all of us, but not all of us are equally vulnerable,” Kear said.

The mobile homes under study were built before 1976, when the U.S. Department of Housing and Urban Development updated construction and safety standards for manufactured housing. HUD updated energy efficiency standards in the 1990s. (The term “manufactured homes” replaced “mobile homes” in the 1990s.)

To be “mobile,” mobile homes were intentionally built “light,” and time and the elements have rendered them even more fragile and dangerous.

Pre-HUD code mobile homes present a list of threats. The old aluminum wiring deteriorates quickly and creates serious risk of fire. It’s also inadequate for powering a modern air-conditioning unit, unless the structure can be completely rewired.

Insulation is practically nonexistent. The sun beats down on the metal rooftops, which are sometimes covered in a thin coat of white sealant to prevent water leaks. Tar holds it together, but falls apart in heat, and the roof starts leaking.

An aged mobile home can be rife with toxic VOCs, including formaldehyde. Airborne asbestos fibers compete with mold. Fixing an aging mobile home could easily cost more than it’s worth — if the structure could survive the renovation.

“They are not energy compliant in any way,” said J.J. Swinney, chief production officer at Habitat for Humanity Tucson. Mobile home residents call its emergency hotline repeatedly to beg for help with homes that are falling apart and mobile home parks that don’t care.

He finds it unconscionable that low-income people are forced into living conditions like these “just because that’s what they can afford.”

“It breaks my heart,” said Swinney, who grew up in a mobile home. There isn’t much that Habitat Tucson can do. “It could cost $30,000 to make them safe,” he said. “They aren’t worth $30,000.”

In Tucson, mobile homes and modern manufactured housing represent more than 10 percent of the housing units in the city of 550,000, more than Los Angeles and Phoenix combined. Of that, 17,000 structures were built pre-1976.

The danger extends well beyond Arizona. Of the 6.5 million manufactured homes in the United States, mostly located in the Sun Belt, from California to Florida, one-third match the deadly substandard profile, research shows.

Esther Sullivan, author and assistant professor of sociology at the University of Colorado Denver, has spent 12 years researching the inequalities plaguing America’s mobile home residents. In her 2018 book, “Manufactured Insecurity,” Sullivan investigates the vulnerabilities and emotional stress that mobile home residents face in parks operated by unscrupulous or greedy managers.

More insidious, she said, is the history of municipal planning that has kept mobile homes in their place: redlining. She lays the responsibility at the feet of society, citing the pervasive stigma of “trailer trash.”

“Zoning has kept mobile home parks situated along interstates and highways, in industrial and commercial zones, and it has kept them out of residential neighborhoods, making them far more at risk of environmental hazards, like flooding and heat,” Sullivan said. “These redline effects last for years.”

As disheartening as the structural conditions of the aged mobile homes are to the researchers, Kear is equally galled by what he sees as their discriminatory financial policies, many of them based on the traditional view of mobile homes as movable, not permanent, housing, when, in fact, they represent one of the last vestiges of unsubsidized affordable housing.

Mobile homes are largely excluded from utility assistance and weatherproofing programs, most notably HUD’s Low Income Home Energy Assistance Program, which helps with heating and cooling costs, bill payments, weatherization and energy-related home repairs.

The reasons for exclusion vary. In some cases, if the home has wheels — whether they work or not — it is deemed ineligible. If it is part of a company-owned park that uses a master meter, the individual homeowner is not considered the utility customer; the company is, Solis said, a situation similar at many multi-tenant apartment buildings.

“There are fewer consumer protections, fewer people serving the community and fewer subsidies,” Kear said. “As a result, it is hard for people to invest in their homes, and if you can’t access lending for improvements, you’ll see [structural] declines.”

Kear and his team recently installed temperature gauges both inside and outside 21 mobile homes in Tucson to get a reading of just how hot it gets. They also interviewed the occupants, whose $20,000 annual incomes are at the poverty level, about what they’ve experienced and what they need to survive in extreme heat.

Kear and his team are driven to get the word out and offer paths to solutions. Solis reports that the fire department in Mesa, a suburb of Phoenix, is now including mobile home parks on summer wellness checks. A utility company is investigating financial eligibility problems, she added, and the county public health department is assessing resources for the mobile home community.

For researcher David Hondula, a health geographer with the Global Institute of Sustainability and Innovation at ASU who studies extreme heat, one solution is overdue. With 2020 as hindsight, Hondula advocates for adding heat itself to the list of disasters eligible for federal resources and funds to protect people, whether they live in mobile homes or on the street. The homeless accounted for 53 percent of all heat fatalities in Maricopa County last summer.

Hondula is heartened that the Phoenix city council approved a budget in May that includes a new Office of Heat Response and Mitigation, one of the first in the nation (last summer both Tucson and Flagstaff declared climate emergencies), but he maintains that the only measure of any study’s success is ending deaths.

Swinney and Ann Vargas, Habitat Tucson’s director of community outreach, dream of buying an empty mobile home park, with utility hookups in place, where they could build new affordable housing, similar to what Habitat for Humanity of Greater Charlottesville has done twice. The latest is the Southwood project.

Deteriorating mobile homes “have been a long-standing issue in our community,” Vargas said. “We don’t want more people to die. We don’t want people to die in our own backyard.”