Category: CO2 strategy

Hot roofs above row house bedrooms cause sleep deprivation; a public health law is needed

Row houses in Baltimore. Black roofs above bedrooms get as hot as 150 degrees.

People who sleep in a top-floor bedroom under a black asphalt roof are likely to lose sleep on summer nights due to heat from the roof, with serious health consequences.  Technically, the fix is simple—coat every black asphalt roof with a white coating—but progress toward that goal is slow.  The answer: a public health law requiring white coating of hot roofs in every city with this problem.

The issue: black asphalt roofs get really hot, keeping people from sleeping well, causing dangerous health problems

Black asphalt roofs, which are common on Northeast urban row houses (townhouses), “can reach temperatures of 150°F or more in the summer sun,” reports the U.S. Department of Energy.  With or without air conditioning, a roof that hot above your bedroom will radiate heat at you all night long.

And people can’t sleep well when it’s too hot.  A research study using data reported by 765,000 people over 10 years found that “increases in nighttime temperatures amplify self-reported nights of insufficient sleep.”

Losing sleep is far worse than a nuisance.  “People make cognitive errors that matter when they sleep badly, whether crashing vehicles or making poor decisions in the workplace,” said UC Berkeley professor Solomon Hsiang in response to the study, as reported by Bloomberg.  He added, “Students learn poorly when they don’t sleep, and consistent lack of sleep harms people’s health.”

And in a heat wave, hot roofs can result in death: in Chicago’s 1995 heat wave, those at increased risk included those “who lived on the top floor of a building (odds ratio, 4.7),” according to a New England Journal of Medicine article.

The technically easy solution:  white roof coating of asphalt roofs

Any roofing firm can apply an “elastomeric” white roof coating to a black asphalt roof, which can reduce a roof’s temperature on a 90-degree day from 150°F to 95°F.  (“Elastomeric” means the coating will stretch with the roof on hot days, and contract with the roof on cold days.)  A homeowner who can safely get up on their own roof, with tools and supplies, can also do the job.  The cost is modest, since the job is relatively small: clean, patch, prime, and apply the finish coat.

But progress in getting black asphalt roofs coated white is slow.  For example, people in Philadelphia have been talking for a decade about this problem, but the Google Maps satellite view of the city shows mostly black roofs, while the roofs that aren’t black are generally gray—a color that provides only about half the cooling benefit of a white roof.

How to persuade landlords to apply white roof coating to black asphalt roofs?

Landlords are under no pressure to apply a white roof coating to their properties to improve their tenants’ health.  Cities could institute a public health measure limiting the temperature of bedroom ceilings, and requiring white roof coating if that temperature is exceeded.  Such a law could presume that black roofs exceed that temperature (and gray roofs as well, if data showed that to be the case).  Then, if a landlord failed to coat the roof white—or provide data proving the bedroom ceilings remained cool enough—the city could do it for the landlord and bill the landlord via the property tax bill.  (In my city, letting your grass grow tall is considered a public health problem, and if you don’t cut your grass the city will cut it for you, and bill you for the work.  So a public health law to prevent sleep deprivation is a no-brainer.) 

Air conditioning is not enough

With or without air conditioning, bedroom ceiling temperatures reached 90 degrees and higher in row houses during a Philadelphia heat wave. Any ceiling above 91 degrees (human skin temperature) will radiate heat to humans, and any ceiling only several degrees below that temperature will make it difficult for humans to radiate heat to the ceiling.

Bedroom air temperatures measured in that study climbed to the 80s/90s in all houses with black tar roofs, with or without air conditioning.

A precedent—recognizing heat as a public health hazard

In Maryland, Montgomery County Councilman Tom Hucker has introduced a bill to make working air conditioning a requirement for all rental units in the county (Bill 24-19). This proposal recognizes that heat is a public health hazard.  Even with air conditioning, a hot tar roof over a row house will radiate heat into bedrooms all night long—and some tenants will limit their use of air conditioning because they can’t afford the bills. Cooling the roof will dramatically reduce heat exposure.


Arlington to add solar on five schools, for largest such procurement in Virginia

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By Will Driscoll

Arlington has solicited bids to add rooftop solar panel systems on at least five schools by 2020, for the largest solar-on-schools procurement to date in Virginia. School system staff designed the solicitation to achieve a competitive price for solar, and to avoid financial headaches such as roof repairs down the road.

The solicitation is structured to attract competition among bidders, yielding a competitive price, by:

• Specifying a larger project size of five schools (with an option for more), rather than the two schools initially envisioned; and

• Reducing the cost of bidding, by providing bidders with ready access to structural and electrical system information for each of the five schools, as well as each roof’s age, type, and warranty information.

The resulting bids will be easy to compare on price, because each bidder must set a fixed price at which it will sell solar electricity to the school system over a period of 15 to 25 years. This contrasts with many existing solar power purchase agreements that specify a starting price and an annual price increase—a more complex approach that is harder to compare across bids.*

The solar-on-schools project has been de-risked in several ways:

• Firms or teams are only eligible to bid if: 1) they have installed at least five similarly-sized projects; 2) they have operated and maintained at least five projects; and 3) they have appropriate contractor and electrical licenses.

• A bidder must state its plan for financing all stages of the project, and provide audited financial statements for the firm (which will be kept confidential).

• The selected contractor must operate and maintain the solar panel systems. (This provision is self-enforcing, since the contractor will only receive payment for the electricity that each system generates.)

• The contractor must specify a method for determining a buy-out price in case the school system chooses to terminate the contract “for convenience.”

Additional provisions address potential roof and durability issues:

• Ballasted systems are preferred, to eliminate roof penetrations that could leak.

• The use of ferrous metals, wood or plastic (e.g., in the solar panel racking system) is not permitted.

• The selected contractor must work with the obligor under any roof warranty to ensure that the warranty remains in effect.

• The contractor must repair any damage to the school caused by the system, including moisture damage.

• In the event that roof repair is needed due to aging of the existing roof, the contractor must remove the solar panel system and then replace it once the repair is completed, at no extra charge; the contractor’s price must account for this possibility.

Arlington’s solar solicitation follows an amendment to the school system’s purchasing resolution, unanimously approved by Arlington’s school board last spring, to permit the use of power purchase agreements under the requirements of Virginia’s Public-Private Educational Facilities and Infrastructure Act of 2002. (Members of Arlington 350 advocated for this resolution.)

Proposals are due from bidders in March, 2018. The school system’s purchasing resolution calls for APS to hire “qualified professionals” from outside the APS staff to review all solicited proposals. These professionals may include an architect, professional engineer, or certified public accountant.

Any rooftop solar offer recommended by the selection committee will be presented at a public hearing, and must be approved by the school board before a contract is signed, per the school system’s purchasing resolution.

Solar installations are to be completed within two years of contract award. The school system may arrange with the selected offeror for solar on additional schools. (A draft timeline from last April anticipated the installation of solar PV systems on two schools in summer 2018.)

Statewide, Virginia could produce 32 percent of its electricity from rooftop solar, according to a National Renewable Energy Laboratories report. Given the increase in solar panel efficiency, from 16 percent assumed in the report to about 20 percent now, the current opportunity is correspondingly higher: we could get 40 percent of our electricity from rooftop solar. Virginia’s approximately 2,100 public schools, with unshaded roofs ideal for low-cost commercial scale solar, represent a promising component of that potential.

Credit is due to Arlington school system staff—in the facilities engineering, purchasing, and legal departments—for their work on the 113-page solicitation, and the amendment to the purchasing resolution that preceded it.

Climate-aware citizens in other communities may find Arlington’s solicitation to be a useful model for their own solar-on-schools initiatives.

*An Arlington bidder may additionally offer, as an alternative to its fixed price, an initial price and an annual price increase, which the school system may select at its discretion.

(Photo: Arlington’s Discovery Elementary School, showing the 497-kilowatt rooftop solar system in a satellite view.  Source: Google Maps.)