Measured result: Roof temperature halved, comfort restored without air conditioning, photovoltaic panels kept in place
The context
In Saint-Jeoire, in the Giffre valley (Haute-Savoie, French Alps), SET Corp designs and manufactures high-precision equipment for microelectronics. Its building has a flat roof in bitumen membrane fitted with photovoltaic panels. With no air conditioning, it overheated every summer: the dark membrane absorbed the heat and released it into the premises. In summer 2025, Hélios treated 1,500 m² of roof with the 4-layer PrimaTherm® reflective system, with the site in operation and without removing the panels.
The results
Roof temperature halved, comfort restored for the occupants without air conditioning, and the photovoltaic installation kept: a bright roof lowers the temperature under the modules, which improves their thermal environment. The coating is elastic and follows the freeze-thaw cycles of the valley; in winter, snow covers the roof whatever its colour.
TODO-ENZO : mesures infrarouges avant / après à intégrer si disponibles.
What this project shows
- Cool roof and photovoltaics: the application is carried out around and under the accessible rows, without dismantling; cable trays, the service duct and the rooflights are protected, then worked around.
- The Hélios method: cleaning and preparation of the substrate, PH169 primer, PH107 reflective base coat in two passes, PH107TCL anti-soiling topcoat, wet-film thickness check, site monitoring sheet. Drums and pump stay on the ground, only the hoses go up.
- The system: solar reflectance 95 % (ASTM E903-12), emissivity 0.89 (ASTM C1371-15), SRI 120 (ASTM E1980), Broof(t3) fire rating; as-built file and warranties handed over at acceptance.
Read next
- Cool roof and solar panels — order of works, module output, albedo.
- Cool roof for industrial buildings — constraints and method on a site in operation.
- Airbus Marignane case study — 5,900 m², −29 °C measured.
