Cool Roofs and Insulation

          A number of roof innovations exist, primarily for the purpose of achieving the optimal thermal performance of a building.

INSULATION is an important factor in achieving thermal comfort for a building’s occupants, since its primary function is to resist heat flow into and out of buildings especially during hot weather; it helps keep the building cool.

COOL ROOFS has a lot of potential for energy savings. The low reflectance of the conventional roofing system causes the surface to reach anywhere between 150° to 190°F. In contrast, cool roof systems stay up to 70°F cooler during peak summer conditions. Most cool roof applications have a smooth, bright white surface that allows them to reflect solar radiation, reduce heat transfer to the interior, and save on air conditioning costs.

Most of the sunlight that falls on a white roof is reflected and passes back into space. But when sunlight falls on a dark roof most of it is absorbed and converted into much longer wavelengths which we know as heat. The atmosphere is transparent to sunlight but opaque to heat, which is why white roofs help cool the planet and dark roofs warm the planet.

 

Most of the roofs are dark-colored. In the heat of the full sun, the surface of a black roof can increase in temperature as much as 50 °C (126 °F), reaching temperatures of 70 to 90 °C (158 to 194 °F). White surfaces reflect more than half of the radiation that reaches them, while black surfaces absorb almost all.

Imagine wearing a white or a black T-shirt on a hot day. By wearing the white T-shirt you will remain cooler than if you wore a black T-shirt because it reflects more sunlight and absorbs less heat. Cool roofs like a white T-shirt; keep the internal temperature of the building cooler.

Of course, making your roof “cool” is not the only option for turning your cool roof into a building saver. Adding insulation can be very helpful as well.

 

SPRAYED POLYURETHANE FOAM (SPF) is applied as a liquid using spray equipment to fill cracks and openings. It then expands nearly 30 times its original liquid volume and dries to form a hard, closed-cell monolithic roof surface. The density of SPF is important when considering strength and thermal resistance. Most SPF roofs have densities ranging from about 2.5 pounds per cubic foot to 3 pounds per cubic foot. 3 pound density foam has an R-value of around 7.00 installed to 6.8 after time.

The R- VALUE of insulation is a measure of its resistance to heat flow; the higher the R-value the greater the insulating properties. R-value is determined by an insulation material’s make-up, thickness and density. R-values of multilayered installation can be calculated by adding together the values of the individual layers. Obviously, the more layers of insulation, the greater the R-value and insulating effect.

Sprayed Polyurethane Foam has to be protected from exposure to the sun's ultra-violet radiation and moisture. This is where the top coating comes in, it helps to protect and seal the foam from any damage.

The coating must be of elastomeric type because a polyurethane foam roof will expand and contract during the course of a day, due to temperature changes on the upper surface of the foam. The coating must be able to stretch with the foam, and return to its normal shape later. The stretching of the coating is technically called elongation. If a rigid coating is applied to the foam’s surface, serious damage can result. As the foam flexes and moves, the coating will crack or rupture, exposing it and beats its purpose.

An ELASTOMERIC type of coating with a bright WHITE color sums up the requirement for protection of the SPF and the reflecting property of a COOL ROOF system; with this, the thermal performance of a building would be optimized, having the advantages of an INSULATION MATERIAL with the benefits of a COOL ROOF.