Energy efficient commercial roofing pairs a reflective surface that keeps the sun’s heat off the building with enough dry insulation to slow the heat that still gets through. White or rated reflective membranes, cap sheets and coatings do the first job, insulation to California’s code level does the second, and regular cleaning keeps the surface reflecting. In California, a commercial low-slope reroof has to meet cool-roof values anyway, so efficiency is built into the replacement. For an assessment of your roof, call NEMA Roofing at 866-631-3366.
Where does a commercial roof gain or lose energy?
- Sunlight absorbed by the surface. A dark roof turns sunlight into heat that flows down into the building. The U.S. Environmental Protection Agency calls solar reflectance the most important property of a cool roof, with thermal emittance (how well the roof sheds the heat it does absorb) also mattering in warm, sunny climates.
- Heat moving through the assembly. Thin insulation lets that heat reach the space below; wet insulation insulates far less than dry.
- Air leaks. The EPA advises pairing cool roofs with insulation and air sealing to get the full energy savings.
What do cool-roof ratings mean?
Solar reflectance and thermal emittance are each measured on a scale from 0 to 1; higher numbers mean a cooler roof. Surfaces get dirty and weather, so California uses aged values, measured after exposure, from the Cool Roof Rating Council’s Rated Products Directory, according to the California Energy Commission. A solar reflectance index (SRI) combines both into one number.
For commercial buildings, the 2025 California Energy Code applies its reroof rule in every climate zone. When more than half of a low-slope roof, or more than 2,000 square feet (whichever is less), is replaced, recovered or recoated, the finished surface must reach two aged ratings, 0.63 or more for solar reflectance and 0.75 or more for thermal emittance, unless it qualifies through a solar reflectance index of 75 or more. Three exceptions matter in practice: a lower reflectance is allowed if the roof and ceiling meet a stricter insulation value; roof area under building-integrated photovoltaic or solar thermal panels is exempt; and roof constructions weighing at least 25 pounds per square foot are exempt.
Why is insulation the other half of efficiency?
The same code section requires the altered roof area to be insulated to the level in its insulation table when a reroof crosses that size threshold, with exceptions such as a recover that adds insulation above the deck, or where rooftop equipment would otherwise have to be disconnected or lifted. A reroof is the practical time to add insulation, because the membrane is coming off anyway. Tapered insulation can add thickness and fix slope to drains in the same layer, and a cover board on top protects it from foot traffic. Any insulation found wet during tear-off should be replaced rather than covered.
Which commercial roofing materials are most energy efficient?
| Material | How it handles the sun | What to check |
|---|---|---|
| White TPO or PVC | Highly reflective as installed; often rated as cool roofs | The aged rating of the exact product and color |
| Modified bitumen with a reflective cap sheet or foil surface | Reflective granules or a metal foil surface add reflectivity to a multi-ply system | Granule loss over time lowers reflectance |
| EPDM | Standard black EPDM absorbs heat; white or factory-laminated reflective versions are available | Field-applied coatings on EPDM need periodic recoating to stay reflective |
| Metal panels | Many factory finishes carry cool ratings, including some darker colors | Aged values for the color, and enough slope |
| Spray foam with coating | Adds insulation and a reflective coating in one system | The coating must be renewed to protect the foam |
| Vegetated (green) roof | Plants and soil shade and cool the roof | Weight and a new membrane underneath; the EPA notes higher first cost and a longer expected life than cool roofs |
The U.S. Department of Defense roofing criteria (UFC 3-110-03) note that weldable thermoplastic membranes come in many colors and are often rated as cool roofs, that metal foil surfaced modified bitumen can be used to achieve solar reflectivity, and that a factory-laminated reflective surface on EPDM outlasts field-applied coatings. For more on reflective products, see our cool roofing service.
Is a reflective roof worth it on the coast as well as inland?
The payoff grows with heat and sun. In the San Fernando Valley, NOAA’s normals for the Woodland Hills Pierce College station show about 115 days a year at 90 degrees or more; on the Santa Barbara coast, the city station’s hottest months average highs near 78 degrees. Inland buildings with large air-conditioned floor areas stand to gain the most. The EPA notes that a cool roof can raise heating use slightly in winter, but that this penalty is typically offset by summer cooling savings, and good insulation reduces it further. Near the coast the code still requires the cool-roof values on a commercial reroof, so the question there is less whether and more which product.
How do you keep an efficient roof efficient?
- Clean low-slope reflective roofs periodically; the EPA notes that ongoing cool-roof costs can include cleaning to keep reflectance up.
- Recoat before a coating wears through, and keep records of product and date for warranty and code purposes.
- Route condensate lines to drains so they do not streak the membrane.
- Find and replace wet insulation after any leak; an infrared scan shows where it is.
- Plan rooftop solar with the roof: replacing an aging roof before panels go on avoids removing them later. Rebates for efficiency upgrades are typically run by utilities or cities, so ask yours before you start.
For how long each system lasts, see durable commercial roofing materials; for the replacement process itself, see commercial roof replacement.
NEMA Roofing installs energy efficient commercial roofs across all five counties it serves, Santa Barbara, Ventura, Los Angeles, Riverside and San Bernardino, with locations in Santa Barbara, Oxnard, Woodland Hills, Tarzana and Downey that put a crew near every served town, inland San Bernardino County included. Read about our commercial roofing service, or call 866-631-3366 to compare reflective systems for your building.
