It depends. On low-sloped roofs (typically found on commercial or high-rise residential buildings), installing a white roof is often a matter of simply choosing the right color coating. If the building needs a new roof anyway, there is no additional cost. If the roof is retrofitted ahead of schedule in order to install a cool roof, there will be some incremental cost. Depending on the kinds of materials used, the incremental cost of choosing a cool roof over a more traditional dark roof for a commercial building is approximately US$0 to US$2.20 per square meter (US$0 to US$0.20 per square foot). When factoring energy savings into the equation, the incremental cost can be fully recovered in many applications over a period of zero to six years.
On steep-sloped roofs (typically found on residential buildings), changing the reflectivity of the roof is usually not as simple. Because most people do not like the aesthetics of a white roof (which would be visible thanks to the sloped nature of the roof), increased reflectivity is best gained through highly reflective shingles that can come in any color. Currently, these roofing materials do cost more than standard materials, but as the market grows, the price is likely to come down.
There are also important non-cost factors to consider:
- Comfort: In unconditioned buildings, cool roofs can maintain cool indoor temperatures.
- Durability: Cool roofs may degrade slower and last longer than similar non-cool roofs, but more research is needed to prove this.