Metal Building Roof Colors and Solar Reflectance
One of the choices one has to make when designing a metal building is selecting the exterior colors. Generally, metal building providers allow you to choose a different color for walls, roof, trim, doors, gutters, and downspouts. Most building manufactures have about 24 panel and trim colors to chose from. When selecting colors, it's important to not only consider the design of the building, but also the Solar Reflectivity.
Solar Reflectivity or Reflectance is the ability of a material to reflect solar energy from its surface back into the atmosphere. The SR value ranges from 0 to 1.0. A value of 0 (darker color) indicates all of the solar energy is absorbed. A value of 1.0 (lighter colors) indicates all of the solar energy is reflected. When a darker color absorbs the solar energy of the sun, that heat is transferred back into the interior of the building.
Also important characteristic to a metal building panel color is the ability of the panel to release absorbed energy, called emissivity. This is called the Solar Reflectivity Index (SRI). LEED requires a roofing material to have a value of 29 or higher for a steep roof pitch >2/12 and 78 or higher for a roof pitch <2/12.
Below is a typical color chart for metal building panels, the solar reflectivity number and the SRI.
If your building location is in a hot zone, and you need to keep it cool in the summer, then one of the best roof panel options is to go with the "Solar White" panel. It will help reflect out the heat and keep the building cooler.
If your steel building project is in an incorporated area, your building department may require your roof to have a minimum SRI value. Houston, Dallas and Austin building departments do require roofs to have an SRI above 78. So if you are planning on building a metal building in these areas, you must go with the "Solar White".
Fortunately, Solar White is not any more expensive than the other Signature 200 colors.