Energy Efficient Roofing
April 28, 2012 | Filed under: Articles, Benefits of Metal Roofing, Home Ventilation
Have you ever wondered what role your roof plays in the energy efficiency of your home? It may be much bigger than you thought!
Transcript…
Hi I’m Todd Miller of asktoddmiller.com. I enjoy using my 30 years of roofing industry experience to bring information to homeowners that helps them make wise decisions concerning roofing and ventilation for their homes. Today I’m going to talk about how your roof can be an integral part of energy efficiency for your home.
Many folks talk about energy efficiency in terms of R-value, and whereas that does play some role in terms of energy efficiency through your roof, it really is kind of a minor player in most types of construction. In most types of conventional residential construction where you have an attic space and ventilation and then a roof on top of that, the bigger things that we want to think about in terms of energy efficiency and the roof system are indeed ventilation and also reflectivity of radiant heat. R-value is important, but realistically R-value is most important down on top of the ceilings of your homes. This we do through insulation on the floor of our attic’s to help hold heat inside our homes during the winter. The fact is if your home is designed to have a vented attic, you want that ventilation to be functioning properly because one of the purposes of ventilation and an attic is to get condensation (or really to get moisture) out of the attic. This is moisture that’s that originates inside your home from cooking, from cleaning, from house plants, from ventless gas stoves, all those types of things create moisture inside the air of your home and that moisture tends to migrate up into the attic. If we don’t have good attic ventilation, then especially during the spring and fall seasons, that moisture is going to collect, in turn into condensation, usually on the bottom side of your roof decking, sometimes on nails that protrude through the decking and things like that. However, because of this moisture that would generate inside of our homes, it tends to collect up in our attics, we want to make sure that we have that attic well vented. Well, if your attic is well vented then R-value (which is attained through thermal mass on top of the roof on top of your roof deck) doesn’t make a lot of sense, because we’re going to get that heat ventilated out, any heat that enters the attic, we’re going to get it ventilated out through good attic ventilation, so R-value doesn’t play a major role.
Again, though the major roles are good attic ventilation so that any heat that does come through your roof system gets vented out and doesn’t collect inside the attic space. Good ventilation requires two things… it requires air intake which is usually soffit vents at the bottom eve edge of your roof, and also good exhaust vents. Exhaust vents a great way to exhaust vent your attic is through Ridge vents at the peak of the attic, but you can also do it through other types of attic exhaust vents as well, or powered vents, turbine vents, things like off-the-ridge-vent static vents, all of those things can be done properly and be used in proper quantity in order to move the air through your attic and make sure that you don’t have a collection of heat and/or moisture inside your attic.
Now, a bigger role that the roof place in terms of energy efficiency can be done through reflection. If we can reflect the sun’s radiant heat during the summer, we can keep that heat out of the attic in the first place, and that just makes our ventilation be even more effective. If we can reduce how much heat gets into the attic, then our ventilation will be even more effective at keeping that attic temperature cooler, and ideally both winter and summer, we would like to have that attic temperature be the same as ambient (the same as the outside temperature). What that means… during the summer if your attic temperature is the same as the outside temperature, then you’re not putting any additional use load or workload on your air conditioner by having a real hot attic that’s hotter than the outside. Likewise, during the winter, having your attic temperature the same as ambient is a very very effective way… really the way… to avoid ice dams and icicles and things like that on your roof. So again, good ventilation is really really important. But if we can reduce the load on that ventilation by reflecting heat out of the attic in the first place, that’s very effective as well.
Now you may ask how do I have a reflective roof? Several ways… you can have a light-colored roofs because light-colored roofs do tend to reflect radiant heat and they’ll keep the attic cooler. There are also roofing systems today (and this is available in metal roofing, which course is one of my favorites) also available in tile roofing, some asphalt and fiberglass shingles are using some new technology which is called a reflective pigment technology. This was actually NASA and military technology developed a number of years ago, but basically it allows for dark pigments to be tweaked if you will in a way so that even in dark colors, the pigment reflects radiant heat. So you don’t necessarily have to have a white roof in order to reflect radiant heat. Again, many of today’s metal roofs feature these reflective pigments. You will also find them in some tile roofs and some shingle roofs as well, but metal roofing is a great way to to achieve that reflection of radient heat through the use of this amazing technology that is called reflective pigments.
Now, another way that your roof can play an integral part in terms of keeping your home more energy efficient is through what I call “above sheathing ventilation.” Now when we talked about ventilation earlier we were talking about ventilation inside the attic that would be beneath the decking or the boards (the roof boards) that are on top above your attic. You can also vent between those roof boards, or between your roof deck and the roofing material itself. This can be done through battens. It can be done through ventilation chambers. There again, it can ideally be done with products like metal, tile. It can also lend itself fairly well to above-sheathing-ventilation. The other way though that we can do above-sheathing-ventilation is by using formed metal roofing products, and this would these would be metal roofing products that look like cedar shake, or perhaps clay tile ,or slate, or really even conventional shingles, but these products have an air gap between the metal and the roof deck. If you’ve ever seen a demonstration of thermal pane windows, you know how a thermal pane window basically has two sheets of glass separated by a small air space, and that small dead air space does amazing things at keeping heat from going through that window. Same thing can be done up on top of your roof with these formed metal shingles that create an air gap between the metal and your roof deck and that air gap or that dead air space is an amazing block for conductive heat transfer. If we can keep that heat from transferring from the rooftop to the roof deck, then that heat does not transfer into the attic, and doesn’t make your attic hotter. If we can keep your attic cooler, then what do we do? We reduce your air conditioning costs.
So thank you very much for tuning in to to this video on how to make your home more energy-efficient through the selection and choice of a good roofing material. Feel free to visit me at asktoddmiller.com and you can always email me your questions… send me pictures of your home. A lot of times folks do that but you can always contact me via email at todd@asktoddmiller.com Thank you very much for tuning in, and I look forward to seeing you in the future.
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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Great video Todd! I’m in the process of adding an addition to my home. We have a metal roof on the existing home and plan to install a metal roof on the addition. Also, I shared your video on our blog as well to help educate others – very helpful website. Thanks for posting!
Thanks so much for your kind words, as well as for posting the video. I do appreciate it! Please contact me anytime I might be of service.