#27 – The Energy Efficiency of Metal Roofing
March 31, 2017 | Filed under: Metal Roofing 101 Series, Roofing Help, Roofing Help Videos
If you’re thinking of a new roof for your home, consider energy efficiency.
Choosing a roof that will reduce your home’s energy costs is a huge ongoing benefit. Metal roofs offer energy efficiency in 3 ways and the important thing is that all of these ways are long-lasting; they do not diminish with age.
1. THERMAL MASS The first way is the very little thermal mass that metal has. Roofing materials such as asphalt and tile will collect and store heat during the day and continue to radiate it into the structure below even after the sun has gone down. Metal roofs, on the other hand, lose any gained heat very quickly once the sun sets or goes behind a cloud or even when a gentle breeze blows across them.
2. REFLECTION OF RADIANT HEAT Next, many of today’s metal roofs feature heat reflective coatings. Even in dark colors, these coatings reflect radiant heat. Products with these coatings have been at times, eligible for tax credits and utility company incentives.
3. THERMAL BREAK Finally, if you choose a metal shingle roof that had integral airspace between the metal and your roof’s decking lumber, conductive heat transfer is blocked as well. This thermal break acts a lot like the dead air space between two panes of glass in a thermal pane window. In fact, we have energy studies showing brown metal shingles keeping the attic space cooler than the highly reflective white standing seam. This is all due to how the metal shingles are formed to stand up off of the roof deck.
The energy efficiency of a metal roof commonly reduces summer electric costs by up to 20% and often even more. If you want to make a lasting impact on your home utility costs, an energy-efficient metal roof can be very wise.
Todd Miller has spent his entire career in the metal building products manufacturing industry. He is president of Isaiah Industries, an organization recognized as one of the world’s leading metal roofing manufacturers. Todd is currently Vice President of the MRA (Metal Roofing Association) and a Past Chair of MCA (Metal Construction Association). Through his website, he strives to raise the bar on standards and practices to provide property owners with the best possible products for successful roofing projects.
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In addition to the three points you make, there is a fourth when you consider the embodied energy of the material–how much energy it took to make and transport the materials in the roof. I couldn’t find numbers on this, but the consensus seems to be that a metal roof has a lower embodied energy than asphalt for a couple of reasons. The primary advantage is that the metal can be recycled at the end of its life, whereas asphalt goes to the dump. Of various metals, zinc might be the greenest due to its prodution process and lower melting point. More here: https://www.rheinzink.us/news/news-detail/article//architectural-zinc-from-gray-to-green/
You are correct. And, yes, recycled content metal has far less embodied energy than virgin metal. In comparison to asphalt shingles, a benefit of metal is the lower weight and hence lower transportation cost / energy use per “square” than asphalt shingles.