About 50 families who live in Baltimore rowhouses likely slept better on hot summer nights this year as their bedrooms were cooler than last year. That’s because they now sleep under a cool white roof, thanks to the Baltimore Office of Sustainability, which each year applies white coating on up to 50 rowhouse roofs.

Most rowhouse roofs in Baltimore are black, and can reach 150 degrees in the summer, radiating that heat to the bedrooms immediately below. A white roof is far cooler in the summer, keeping bedrooms cooler — and people need a cool bedroom to get a good night’s sleep.

Beyond the issue of comfort, excess heat in bedrooms likely causes health problems. To assess some of these potential health effects, Johns Hopkins University has launched a $1 million study in collaboration with Baltimore City.

“It’s well known that high temperatures negatively affect sleep quality,” while “insufficient sleep is a major public health problem,” said Professor Adam Spira of the Johns Hopkins University Bloomberg School of Public Health, in an email to me.

In Baltimore City homes, he said, “bedroom temperatures can stay above 90 degrees for several days in a row, even when outdoor overnight temperatures fall below 77 degrees.” Insufficient sleep, he added, “is associated with an increased risk of motor vehicle accidents, depression, Alzheimer’s disease, heart disease and mortality. So it’s really important to optimize sleep, to improve health and potentially reduce health disparities.”

The Johns Hopkins study will recruit volunteers from among those whose roofs will be coated white by Baltimore City. Researchers will measure participants’ heart rate, blood pressure, sleep, and other health indicators next summer, before and after their home receives a white roof coating. If the indicators look more favorable after white roof coating, this would suggest that the white roofs had improved public health, not just comfort. The study will also fund coating of several of the rowhouse roofs.

Although white roofs on row houses have been promoted as a way to save energy, and even to cool entire neighborhoods if applied widely enough, the health of rowhouse residents is a more immediate concern.

The technical fix is simple yet progress has been slow. To get beyond fixing the hot roof problem for 50 row houses per year, and to help ensure that all rowhouse roofs are promptly coated white, Baltimore needs a public health measure.

Two years ago, I raised the issue of hot rowhouse roofs and sleep deprivation in an email to the vice dean of the Bloomberg School of Public Health at Johns Hopkins Josh Sharfstein.

I suggested that a new public health law may be appropriate to address the problem. A faculty member at the school had advised me that City Council members, before they would vote for any new public health law, would need to see data showing that a new law was needed. Dr. Sharfstein forwarded my email to Dr. Spira. That is what led to the research into the link between white roofs, temperature and health.

At this point, the Johns Hopkins researchers have reason to believe that white roofs may improve sleep quality and health. Their study will provide an initial assessment of whether white roofs do have that positive effect, and if so, just how much of a benefit they provide.

So it seems like the right time to start talking about a solution as we await the research results.

Just as cities require landlords to provide for heat in the winter, by providing heating equipment in working order, a city may require landlords to prevent excess heat in the summer in buildings with flat asphalt roofs. Renters can do nothing about the problem of hot roofs, as they lack both the money and the legal authority to hire a roofing crew to apply white roof coating.

The Baltimore City Council should enact a public health law protecting renters from the excessive heat from these roofs, by requiring landlords to apply white roof coating.

For any landlord who does not comply, the city would need to coat the roof white and bill the landlord through the property tax bill. If any landlord did not pay their property tax bill, the city is legally authorized to possess the property, sell it, and give the landlord the net proceeds — that is, the sale price, minus the property tax bill, minus the cost of selling the property.

Once Baltimore starts coating rental rowhouse roofs white as needed — and billing the landlords — the city could also offer white roof coating to families who own the rowhouse in which they live, for the same cost as for landlords.

William L. Driscoll (William.L.Driscoll @comcast.net) is the founder of White Roofs for Public Health.