The Use of Color in Roofs for Steel Buildings
Reflectance plays a major role in determining a steel building’s heat build up under the sun. The use of “cool roof” initiatives has become a 21st century technology improvement to help improve steel building’s resistance to heat.
Roofs employing infrared reflecting pigments in their make-up will stay cooler than roofs featuring non-reflective pigments of the same color, thus keeping the steel building that much more cooler.
Reflecting of heat and light is only a partial solution to the dissipation of light and heat away from a steel building. Any heat that is not reflected is absorbed by the structure. A steel building will react to exposure to light by absorbing it, reflecting it, or transmitting the light. All light introduced to a roof is either reflected or absorbed. Certain pigments in paint on a roof will reflect away much of the sunlight introduced. That light which is absorbed by the roof and coordinate steel structure is converted to heat within the building.
Heat build up within a steel building is dissipated by either radiation, convection, or conduction. Radiation is the emission of radiation of energy away from the roof. Convection is the transfer of heat from the steel building into the air. Conduction is the movement of heat through solid materials from a high temperature area to a low temperature area. In a roof on a steel building conduction travels from the roof’s surface, then underneath, through the decking, rafters, joists, walls and then throughout the entire structure. Convection and conduction make heat easy to draw into a steel structure.
An uncoated steel roof will build up an ample amount of heat while under the sun. Coated steel roofs will radiate a great deal of the sun’s heat away from the roof and structure. The reflectivity of roof characteristics can greatly impact the amount of energy cost utilized for the interior of the building.
The dissipation of heat from the sun via the radiation process can only effectively be brought about by absorption of the introduced light. Highly reflective roofs then, by definition, are not going to be as efficient in heat blockage because the proven heat reducing capacity of certain pigmented paints has not been employed.
Some states have built the painted roof particulars into their codes. The roofing material needs to be coated with a durable paint finish specified by code.
The process of introducing reflecting pigments into the roof paint offers the consumer a proven and long lasting vehicle to maximize reflectance characteristics of the roof and, subsequently, the entire steel building. No sacrifice of color pigmentation robustness is necessary.
The use of cool roofing helps building designs that are gentle on the environment by enhancing the interior cooling of the structure, conservation of energy resources, and comfort for the structure’s occupants. Cool roofing will play more and more of a part in future steel building construction.