Roofing: Making White Coatings Work

The main purposes of white coatings is to protect roof membranes, resulting in longer roof life cycles, and to reflect solar radiation, resulting in lower energy costs. A closer look at their formulations and components can help you successfully specify and apply coatings and ensure maximum performance.

Binders, pigments, liquid carriers
In general, a white coating consists of a binder blended with pigments and other additives. There are hundreds of different white coating products formulated and manufactured by a range of companies. Most can be conveniently classified according to the binder they use. Most white coatings used today are water-based - often referred to as latex coatings - and are available in a variety of polymer types. For some white coatings, organic solvents carry the liquid, while others, called reactive coatings (generally prepared with multiple-part resins blended on site before curing), might flow well enough to eliminate the need for a liquid carrier.

Membrane Compatibility
You can specify white coatings for use on most roofing membranes and systems. They most commonly are applied to metal roofs, single-ply rubber roofs and modified bitumen roofs. But they can be applied to certain kinds of asphalt built-up roofs. Prior to specification, you will need to establish the compatibility between the coating and the underlying roof surface. You can do this by consulting with a RAMCON representative

Primers and Surface Preparation
Primers are useful for improving the adhesion between roof surfaces and coatings and for imparting additional properties to roof coating systems. A compatible primer for a rubber roof coating might provide better adhesion to a rubber roof membrane or improve a coating’s permeability rating on a sprayed polyurethane roof.

Application Insights
We typically use airless sprayers, rollers or brushes. Due to the variety of coating types, climactic conditions and surfaces to be coated, it’s important that we utilize the proper application rates and related recommendations.

Many, but not all, white coatings are waterproof. A coating’s permeability to liquid water, water vapor, and gases varies greatly, depending on the coating type:

• Acrylic coatings are breathable, so they have a high moisture-vapor transmission rate, or permeability.
• Silicone coatings are classified as breathable.
• Butyl rubbers, hypalons and neoprenes have very low permeability, so they are highly resistant to moisture transmission.

Cleanliness and Aging
The frequency and intensity of precipitation, along with the slope of the roof, will affect the cleanliness of coatings over time. As with other white surfaces, white coatings can discolor and darken slightly after several years of service. Generally, a small decrease in reflectivity occurs over time, depending on several factors. Wind-blown dirt and dust can decrease the reflectivity of white coatings, depending on the coating’s age and regional climate characteristics. To prevent this, your roof can be re-coated periodically, which is significantly less expensive than the original coating.

Whether you are looking for a reflective coating to reduce the energy costs of your facility, are seeking valuable LEED points or are looking to extend the life of your system, trust the professionals at RAMCON. We’ll be able to put together a solution, utilizing the right coating for the job and at the right price.