On site research proves that it is possible to save as much as 70 percent on energy with a “cool roof”. This is because cool roofs reduce roof temperatures by reflecting heat and sunlight away from the building.
This is according to the United States Environmental Protection Agency (EPA) that has based its findings on infield monitoring of more than 10 buildings in Florida and California. The Agency has also stated that cool roofs have the ability to reduce both greenhouse gas emissions and air pollution.
While the concept of cool roofs isn’t new – they have been in use for more than two decades – they clearly are not used widely enough.
Understanding the Concept of Cool Roofs
Cool roofs are one of the most exciting energy efficient roofing ideas to have grown out of our need to make building design sustainable. Essentially an umbrella term for a number of different but related concepts, a cool roof will reflect heat and sunlight rather than absorb it. Properties in the materials used ensure that the roofs stay considerably cooler than roofs constructed using conventional materials.
While conventional materials used for roofing absorb between 85 and 95 percent of the sun’s energy (and heat), they only reflect 5 to 15 percent of this energy. Cool roofs, on the other hand, reflect a massive 65 percent, and absorb no more than 35 percent of this energy.
High thermal “emittance” (which is the ability of the material to release heat that has been absorbed) is also important, especially when climatic conditions are generally sunny and warm. In practice scientists use either a number between zero and one, or a percentage between one and a hundred to indicate emittance. Except for metal roofs, most materials emit (or release) more than 0.85 or 85 percent of the heat that is absorbed.
Understanding the Benefits of Energy Efficient Cool Roofs
Since energy absorption is lowered in summer and winter, total annual energy savings may be estimated by comparing lowered costs in summer with increased heating costs in winter. Even with this so-called “winter penalty”, research findings show that the overall savings range from 20 to 70 percent annually.
Even where cool roofs are utilized, it is necessary to use an air conditioning system to efficiently reduce energy. If air conditioning is not used, comfort will be improved, but there won’t be any appreciable energy saving. When air conditioning is used, the interior of the building will be a lot cooler in summer with considerably less energy usage.
Taking this a step further, it is because cool roofs lower energy use that they consequently reduce greenhouse gas emissions and air pollutants.
Of course the human comfort factor is also very important. With or without air conditioning, cool roofs lower air temperatures inside buildings and thus help to prevent illnesses and human conditions associated with heat.
A dark roof is not energy efficient
That’s correct! A dark roof can absorb a lot of heat from the sun, which can increase the temperature inside a building and make it harder to keep cool. This can lead to higher energy costs for air conditioning and can also contribute to urban heat island effects in cities.
In contrast, a light-coloured or reflective roof can help to reflect sunlight and heat away from the building, reducing the amount of energy needed to keep the interior cool. This can result in lower energy bills and a more comfortable indoor environment.
There are also other factors to consider when it comes to the energy efficiency of a roof, such as insulation, ventilation, and the type of roofing material used. However, choosing a light-coloured or reflective roof is generally considered a good strategy for reducing energy use and improving efficiency.