Why cool metal roofs are way cool?

Why Cool Metal Roofs are way Cool?
A cool metal roof reflects and emits the sun’s energy as light back to the sky instead of allowing it to enter the building below as heat. In many climate zones, a cool metal roof can substantially reduce the cooling load of the building, providing several direct benefits to the building owner and occupants:

• increased occupant comfort, especially during hot summer months

• reduced air conditioning use, resulting in energy savings typically of 10-30%¹, and

• decreased roof maintenance costs due to longer roof life.

In addition to these well known benefits to the building owner, cool metal roofs benefit the environment and public health in far more ways. As recognition of these benefits has become more widespread, cool metal roof requirements are appearing in building energy codes and green building programs across the nation.

Cool metal roofs directly reduce green house gas emissions by conserving electricity for air conditioning therefore emitting less CO2 from power plants. Cool metal roofs also cool the world independently of avoided carbon emissions, simply by reflecting the sun’s energy as light back to the atmosphere, thereby mitigating global warming. A Lawrence Berkeley National Laboratory study found that world-wide reflective roofing will produce a global cooling effect equivalent to offsetting 24 gigatons of CO2 over the lifetime of the roofs. This equates to $600 billion in savings from CO2 emissions reduction.²

Climate Change
Mitigation

Cities can be 2° to 8°F warmer than surrounding areas due to dark materials, including roofs, which absorb the sun’s light energy as heat during the day and release it at night as heat.3 This phenomenon removes the opportunity for air to cool down at night and results in higher temperatures being maintained longer. By immediately reflecting solar radiation back into the atmosphere and reemitting some portion of it as infrared light, cool metal roofs result in cooler air temperatures for the surrounding urban environment during hot summer months.

Urban Heat
Island Mitigation

Cool metal roofs, through mitigation of the urban heat island effect and reduction of ambient air temperatures, in turn improve air quality. Smog is created by photochemical reactions of air pollutants and these reactions increase at higher temperatures. Therefore, by reducing the air temperature, cool metal roofs decrease the rate of smog formation.

Reduced Smog

Lower ambient air temperatures and the subsequent improved air quality also result in a reduction in heat-related and smog-related health issues, including heat stroke and asthma.

Public Health
Benefits

Because cool metal roofs reduce air-conditioning use during the day’s hottest periods, the associated energy savings occur when the demand for electricity is at its peak. Therefore, use of cool roofs reduces the stress on the energy grid during hot summer months and helps avoid shortages that can cause blackouts or brownouts. In addition, for building owners that pay for their energy based on the time of use, they save energy when it is at its most expensive – and hence, save more money!

Peak Energy
Savings and Grid
Stability

Cool metal roofs directly reduce the air conditioning use for buildings by reducing heat gain in the building below, but they also indirectly reduce air conditioning use in urban areas by helping lower ambient air temperatures. Therefore, with cooler daytime temperatures, buildings and vehicles use less air conditioning and save additional energy. In turn, this results in a reduction in the CO2 emissions from electricity generating power plants.