If you've ever picked up a piece of metal that has been baking in the hot sun all afternoon you know how unpleasant that it can feel when it burns your hand. Likewise, being on a metal roof during the heat of summer can be rather unpleasant (granted being on an asphalt roof in the middle of summer will feel exactly the same). Logically, it seems that because metal is so hot in the sun it must contribute to the heat in your attic space that challenges your home's air conditioning system. Right? On the contrary. Metal roofing is one of the most energy efficient roofing materials that you can install on your home.
While metal roofing is definitely hot to the touch when it's been sitting in the sun all afternoon, it is important to understand the science behind the heat. If you have asphalt shingles on your home then you may be familiar with a scenario similar to the following: as temperatures rise during the day your home begins to heat up and your air conditioning unit kicks on to regulate the temperature in your home. As the sun sets and the atmosphere cools down you may have noticed that your air conditioner is still kicking on well in to the evening and perhaps even into the night hours. Sometimes it can even feel like it is cooler outside than it is in your home. But, why? The reason behind this is pretty simple, energy retention. If you've ever been on your shingle roof of the evening you'll notice that your shingles are still warm well into the evening hours. This is because of energy retention. Asphalt shingles typically reflect as little as 3% of solar energy which means up to 97% of solar energy is being absorbed by your shingles! As your shingles absorb heat your attic space heats up substantially. As your attic space heats up it will eventually over-saturate your insulation and begin to make its way into your living areas. This is why your AC will still be attempting to regulate your home's temperature even after the air outside your home has cooled.
Enter metal roofing! Your first thought may be, if shingles make my house hot then metal roofing must REALLY make it hot. In reality, the opposite is true. Quality metal roofing like we manufacture at Best Buy Metals is coated with industry leading SMP or PVDF pigments which are extremely energy efficient. On average, quality metal roofing reflects 25 - 65% of solar energy (compared to asphalt's 3-15%). In fact, the coatings we use at Best Buy Metals are certified by Energy Star as having an initial solar reflectance of at least 0.35. The true solar reflectance varies based on the color and pigments used in the metal roof coating, but your manufacturer should be able to provide you an SRI (Solar Reflectance Index) number for the color you choose.
While metal roofing gets hot during the day, it is reflecting a large portion and even a majority of the solar energy that is hitting it. If you were to touch your metal roof as the air temperature began to go down, you would notice that your metal roof is cooling rapidly. This is why choosing an energy efficient roof system can have a direct impact on your heating and cooling costs. If metal roofing is reflecting solar energy as opposed to absorbing it that means the insulation in your attic space becomes less saturated during the day and is not transferring nearly as much heat to your living area during the day, evening and night time hours.
There are other steps you can take to making your home more energy efficient including the type of insulation used, attic ventilation and more; however, as the first line of defense against the heat and elements your roof is one of the most important steps to achieving maximum efficiency.