In late March, the Sun crosses the equator and begins to move into the Northern Hemisphere. (We know that the Sun is stationary and Earth is moving, but it is easier to think about it the other way around.) Temperatures rise, perennials bloom, and we’re glad that winter is over. It’s a great time of year. The heavy coats go back into the closet and everyone’s attitude brightens. But we all know those warmer spring temperatures will eventually turn downright hot in summer. Some say it’s getting even hotter due to global warming. A prepainted product is on the market that can help mitigate environmental concerns raised by increasing temperatures. It’s called cool roofing and it continues to rise in popularity.
Over the past few years, we have seen a significant increase in the use of metal roofs in the residential sector. In fact, the Metal Roofing Alliance estimates that more than 750,000 U.S. homeowners chose a metal roof to protect their families in 2015. According to their survey, the Metal Roofing Alliance identified eight reasons homeowners are making the switch to metal roofs. Here is a breakdown of the four most popular reasons people are using metal roofs to protect their homes.
1. Metal roofs have longevity.
Depending on the material, metal roofs can last anywhere between 40 and 70 years. That’s a significant increase when compared to the life expectancy of a traditional asphalt roof, which may only last between 12 and 20 years.
In the arena of university R&D, one often thinks, who cares? I certainly do. But in this and the next post, you will read about some fascinating work coming out of Stanford University. As a self-professed cynic, I would never mention “the next great thing” if I did not see some very real potential. There is, of course, a big valley between R&D and commercial reality, but from what I have heard and read … well, you be the judge.
One of these ideas that could fall into the “too good to be true” category is radiative cooling. Before you fear that I’ve taken leave of my senses, yes, I do understand that all objects radiate energy and will cool as a result. All cool-roofing codes contain an emittance requirement for this reason. Objects (such as painted metal roofing) with a high thermal emittance (>75%; a perfect emitter would be 100%) cool down faster than low-emittance materials such as shiny metal. When the sun sets, you want the roof to radiate as much heat as possible to the atmosphere as fast as possible. Of course, when the sun is beating down on the roof, you also want the roof to reflect as much heat as possible in the form of infrared radiation (IR), keeping the roof as cool as possible. That’s why both parameters—reflectance and emittance—are important in the cool-roofing arena. Continue reading →
We are now a few decades into the era of cool metal roofing. “Era” is probably the wrong word, because cool metal roofing is here to stay. Many coatings producers and metal roofing manufacturers in North America now offer the benefit of cool roofing as a part of their standard product portfolio.
As “special” becomes “standard,” it is easy to assume that cool roofing is on autopilot and that nothing more needs to be done. Although in a practical sense this is mostly true, it is good to remember that research continues wherever energy savings is the goal, and cool roofing is included in this research.