Tucson Roof Gurus is here today 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 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 values most important down on top the ceilings of your home’s. This we do through insulation on the floor of our attics 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 in an attic is to get condensation or really to get moisture out at the attic. This is moisture that originates inside your home from cooking, from cleaning, from house plants from vent less gas stoves, all those types of things create moisture inside the air 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 and turn into condensation, usually on the bottom side of your roof decking, sometimes on nails that protrude through the decking and things like that is where it will hit first. 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 as well vented then R value which is attained through thermal mass done 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 a soffit vents at the bottom eve edge of your roof and also good exhaust vents.
Exhaust vents are 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 of the ridge vents, static vents, all of those things can be done properly and will 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 plays 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 are 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 does that mean during the summer, if your attic temperature’s 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 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 roof.
Light-colored roof 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 of course is one of my favorites, also available in tile roofing, some asphalt and fiberglass shingles are using some new technology which is called 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 reflexes 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’ll also find them in some tile roofs and some shingle roofs as well but metal ripping is a great way to achieve that reflection of radiant heat, through the years 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 efficiency is through what I call above sheathing ventilation.
Now when we talk 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 of your, that are 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 batons, it can be done through ventilation chambers and there again is can ideally be done with products like metal, tile, can also lend itself fairly well to above sheathing ventilation.
The other way that we can do above sheathing ventilation is by using formed metal roofing products and this 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. Now if you’ve ever seen a demonstration of thermal pane windows, you know how thermal pane window basically has two sheets or two panes of glass separated by small airspace and that small dead airspace 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 for transferring from the rooftop to the roof deck, then that heat does not transfer to the attic, 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 reading about how to make your home more energy efficient through the selection and choice of a good roofing material. We hope that if you have any roofing questions, you’ll feel comfortable calling us at Tucson Roof Gurus.