Cool roof coating

A cool roof coating is a white or very light material with high reflectivity. Instead of soaking up the sun and heating the slab, it sends most of the radiation back. The roof stays cooler, and the floor below heats up less in summer.

It is usually a white elastomeric or polyurethane coating, applied as the top coat over the waterproofingWaterproofingThe work and materials that stop water getting through on flat roofs, balconies, bathrooms, basements, planters and tanks. or over spray polyurethane foamSpray polyurethane foamA foam sprayed on as a liquid that expands on the spot and sets into one seamless layer. It insulates against heat and cold and closes cracks and joints.. On its own it replaces neither waterproofing nor thermal insulationThermal insulationA layer of material that lets heat through only slowly, so a home keeps its warmth in winter and stays cool in summer.; it adds to them.

Reflectivity drops as the surface gets dirty with dust, leaves and sootSootThe black, greasy dust that smoke leaves on walls and ceilings after a fire, or from a fireplace or stove. Paint straight over it without cleaning and priming and it comes back through.. An occasional wash and renewing the coat once it wears keep it working. Where people walk often, the white wears faster.