|
The heat build-up within a steel building is, in large part, determined by the building’s roof reflectivity under the sun. “Cool roof” technology initiatives have been applied in the 21st century to help improve any steel building’s resistance to heat. Roofs that have non-reflective pigments of the same color will not dissipate and reflect heat as roofs employing infrared reflecting elements in their composition. Infrared reflecting elements on roofs keep steel building interiors cooler.
The reflecting of light and heat is only a partial answer for the need to dissipate light and heat away from the steel building. Heat that is not reflected by the roof is absorbed into the structure. Steel buildings will react in one of a combination of three ways with exposure to light ““ it will absorb, reflect, or transmit the light. Any light introduced to a steel roof is either absorbed or reflected. Much of the sunlight introduced to the roof can be reflected away successfully with the use of certain pigments in the paint of the roof. Remember that light that is absorbed by the roof and the steel structure of the building is converted to heat within the building.
Radiation, convection, or conduction will dissipate the heat build-up within a steel building. The emission of energy away from the roof is called radiation. The transfer of heat from the steel building into the air is called convection. The movement of heat through solid materials from a high temperature area to a lower temperature area is called conduction. In relation to a roof on a steel building, conduction will travel from the roof’s surface, then go underneath, through the decking, rafters, joists, walls, and ultimately throughout the entire steel structure. The processes of conduction and convection make heat easy to draw into a steel building.
There will be a large amount of heat built up by an uncoated steel roof while exposed to the sun. A large portion of this heat can be radiated away from the roof and structure with the use of a coated steel roof. The amount of energy expenditure within the building to keep it cool will, in large part, be determined the roof’s reflectivity.
Absorption of any light introduced by the sun is essential to dissipation of this same heat by way of the radiation process. The use of highly reflective roofs then, in contrast, will not be as effective in heat blockage because the proven heat reduction capacity of certain pigmented paints has not been applied.
The painted roof stipulations, in some states, have been written into their building codes. The code specifies that the roofing material needs to be coated with a durable paint finish. The steel building purchaser should consider introducing reflective paint pigments onto the roof to maximize reflectance of the roof and, subsequently, the entire structure. The paint will not dull. “Cool roofing” will play more and more a part in the future of steel building construction.
|
