Cool roof for school buildings

French heatwaves now spill into the end and the start of the school year. A dark flat roof absorbs solar radiation all day long. It stores that energy and releases it towards the volumes below, including in the evening. Top-floor classrooms, gyms and enclosed covered playgrounds are the first affected, with a large roof surface right above them. Without air conditioning, nothing offsets that heat: the temperature climbs in the morning and barely falls back. The Covalba blog covers this mechanism in its article on thermal discomfort, and in the one devoted to the urban heat island, a familiar effect around inner-city schools.

In education, a project is judged first on its calendar. A school roof is treated during the holidays, at autumn half-term, in spring or over the summer depending on the surface. Cool roof lends itself to this. The application is carried out from the outside, the machines stay at the foot of the building and only the hoses go up. No classroom is taken out of use, no furniture is moved, no room is shut down. The duration runs from a few days to a few weeks depending on the surface, leaving a comfortable margin before pupils and staff return.

School estates are dominated by flat roofs with a bituminous membrane, often laid more than ten years ago, and by steel deck on gyms and extensions. Eight Covalba projects out of ten involve a bituminous membrane over ten years old. Fiber cement and concrete are also found on technical buildings and covered playgrounds. The technical diagnosis decides: CovaTherm on a sound substrate, CovaSeal 20 when the waterproofing is tired and needs a rework, CovaMetal 20 on a corroded steel deck. Our bituminous membrane and steel deck pages cover each case.

A school building over 1,000 m² falls within the scope of the décret tertiaire (French tertiary decree). Consumption must fall by 30% by 2030, 40% by 2040 and 50% by 2050, with an annual declaration on the OPERAT platform. Cool roof acts on the cooling load and on the heat received by the building, without heavy works on the envelope. For staff, French labour law sets no maximum temperature but requires the employer to protect workers from heat. Our article on the décret tertiaire sets out the thresholds and the trajectory.

Funding follows ownership: the town for primary schools, the department for lower secondary schools, the region for upper secondary schools. The Fonds Vert, a French state fund, remains the main lever for local authorities through its energy renovation and summer comfort strand. The CEE BAT-EN-112 grant is not open to them, but a private school or a campus under tertiary status can look into it. Below €100,000 excluding VAT, the contract is awarded without a formal procedure, as our local authorities page explains.

A cool roof comes to €20 to €25 per m² supplied and applied. A new membrane sits between €80 and €100 per m², an insulation plus waterproofing rework around €150 per m². On a school complex, that budget gap weighs heavily on the decision. The coating protects the roof from UV and thermal shocks. It pushes the membrane replacement back by 8 to 10 years, time enough to plan a heavy refurbishment within a multi-year programme. A polyurethane system with a finishing topcoat lasts 8 to 10 years, against 2 to 5 years for the acrylics on the market.