Building owners and managers fortunate enough to have a metal roof know personally its durability, resiliency and reliability, not unlike that contributed to the U.S. Postal Service of yore: “Neither snow nor rain nor heat nor gloom of night …”—nor fire, nor hail nor the like—will prevent it from fulfilling its function. Those natural elements conspire to knock on the good reputation of a metal roof, to no avail. But how does a metal roof hold up against a more ominous threat… lightning?
The Myth of Metal Roofs & Lightning
Metal conducts electricity, so it’s not unreasonable to have concerns about whether a metal roof is the best material with which to build a roof to avoid damage from lightning.
Topography in the area of the structure: The probability of a strike is higher if a structure is situated on a mountaintop or hilltop as opposed to a field.
Size and height of the subject structure. A tall building or a facility covering a large ground area is more likely to be struck than a short or small building. A tall, thin structure, such as a tower, a tree or utility pole, is also a more likely target for a lightning strike.
Relative location of the structure with respect to nearby larger and taller structures. A very tall structure located near a small, short one will tend to further reduce the likelihood of a strike to the smaller one.
Frequency and severity of thunderstorm activity in the geographic area of the project.
Notice there is no mention of the material from which the structure is made. In fact, the probabilities of a strike to a metal roofed structure are no more or less than any other kind of structure. The probability risk has more to do with the height and size of the structure and its surroundings than the material of which it is made.
The use of a lightning protection system, such as lightning rods, may lessen the consequence of a strike. And if lightning does strike a building, a metal roof actually can cause the energy impact to disperse evenly and uneventfully through the structure. Finally, metal roofing isn’t combustible or flammable.
Metal is Best Overall Roofing Material
Bottom line, metal is probably the best material option for roofing, and a safer source of protection for your facility , customers and employees when the inevitable storms come.
Metal roofing material is known for its durability, but it also offers two other sustainable attributes that are sometimes overlooked: enhanced energy-efficiency and high recyclability.
Cool Roofs
When coated with a light-colored reflective paint, metal is a superior material for a cool roof. A three-year study on the energy efficiency and service life of metal roofs by Oak Ridge National Laboratory’s Buildings Technology Center found that the high solar reflectivity and emissivity levels of cool metal roofing can greatly mitigate urban heat island effects. The study used a solar spectrum reflectometer and an emission meter to test the efficacy of cool metal roofs.
Most Efficient Metal Roofing Color
Oak Ridge found that white coatings on other roofing materials displayed a 25% to 40% drop in their initial reflectance, but the metal roof tested retained 95% of its initial solar reflectance during the length of the study. Depending on the color of a painted metal roof, the reflectance ranges from 10% to 75%, which compares very favorably with the 5%-to-25%-range of an asphalt roof.
Recyclability of Metal Roofing
Metal is also highly reusable, and metal roofing material rarely ends up in landfills. Many metal roofs contain up to 40% recycled steels. Their material is also 100% recyclable. Research conducted by the Florida Department of Environmental Protection found that metal is one of the best eco-friendly roofing materials from a waste-reduction standpoint.
All in all, metal is among the most sustainable roofing materials, especially when you consider that metal roofs can last more than 60 years.
Have you ever been under a metal roof that had condensation on the bottom side of it? It is quite annoying to have the condensation falling on you like rain. Worse, if the roof is over your shop, carport, barn or self-storage unit, you have to worry about what damage it is doing to the contents of these buildings. Oftentimes people will insulate their metal roof with vinyl-backed fiberglass insulation to prevent humid air from coming into contact with the cooler metal roof, which may be at or below the dew point. If you are heating or cooling a building, adding insulation would certainly be a good idea. But what about buildings that aren’t heated or cooled? If you don’t want to put vinyl-backed insulation in your roof, what other options are there?
How Dr!pStop Can Help
The answer is a product called Dr!pStop, which is a felt-like material with a rubber backer that can be applied to the back side of metal panels that will trap the moisture as the condensation forms. When conditions change, usually the ambient air temperature rises raising the dew point, the moisture is released from the Dr!pStop material back into the air. MBCI can apply this material to the back of its coils (either Galvalume® Plus or painted) and then roll form the metal into MasterRib® and PBR panels.
The Dr!pStop material is a very tough, light gray material that resists ripping, tearing or deterioration. It resists dirt and grime; is antimicrobial and is very easy to clean with a hose or pressure washer. The rubber backer on the material helps protect the back side of the panel from corrosion, though there is no protection at the panel’s cut edges. The material is approved for smoke generation and flame spread per UL 723. It also is good for acoustics and helps dampen sound from either inside or outside the building.
Roof panels with Dr!pStop are ideal for use in industrial plants, sports areas, aircraft hangars, non-climate controlled self-storage units, garages, carports, garden centers and many other buildings.
In an effort to cut electricity costs and to help the environment by burning fewer fossil fuels, photovoltaic (PV) arrays are becoming very popular in spite of their significant installation costs. To further stimulate this trend, the DOE’s SunShot Initiative has been created to make solar energy costs competitive with other forms of energy by the end of the decade in an effort to drive widespread adoption of this renewable energy technology.
At the same time, in many areas of the country, electric energy providers are struggling to meet the growing energy demand during peak times of use. While they need to be able to provide sufficient capacity during these times, they don’t want to spend billions of dollars to build additional capacity that is only needed for a small portion of weekdays in the summer (and at night in the North during the winter). To help reduce electrical usage during these peak times, smart meters have been introduced and time of use (TOU) electrical rates are now offered, which charge more for electrical use during peak times and less during off peak times. Currently, in most cases, TOU is optional but, in a growing number of areas, is becoming mandatory.
Save Money with a Solar Energy
Obviously, if you are on a TOU plan, you will want to minimize your electrical usage during the peak times. But, another way to save considerable money on your electric bill is to install a solar array on your metal roof. During the summer peak time when the electric company charges you the highest rate for your electricity, your PV array will be generating the most electricity to offset your usage. This helps both you and the electric companies save money – you save on your electric bill, and the electric companies hope to reduce the need for additional generation capacity.
Installing a PV Array
The best place to install a PV array is generally on your roof, be it a home or commercial building. This keeps the equipment out of the way yet reasonably close to the building’s electric meter. So, if this is the best place to install a solar array, will my roof handle it? What do I mean by that? A flexible thin film PV array weighs about ¾ pound per square foot and a glass-based crystalline PV array weighs 3-4 pounds per square foot so your roof must be capable of supporting this additional weight. Your roof should also have minimal shading and a life expectancy equaling or exceeding that of the solar array. Otherwise the roof will have to be replaced one or more times during the approximate 30 year life of the PV array. This is especially true if the existing roof is 5-10 years old when the PV array is installed. Removing and installing the PV array adds a huge additional cost plus to the cost for the roof replacement(s).
Installation of glass-based crystalline on an SSRM
Is Your Roof Solar Ready?
So, what should a person do? Whether you are a homeowner or a commercial building owner, you should seriously consider ensuring that you have a “solar ready” roof. You may not want a PV array now, but if you decided to install one in the future, the roof would be capable of accepting it, and, just as important, last as long as the PV array. This would be easy to do with new construction but can also be done when it’s time to reroof. This is a hot topic in California where the California Energy Commission recently approved a new energy standard that includes a requirement for all residential and commercial buildings to have “solar ready” roofs beginning January 1, 2014. So what is the best roof type for a “solar ready” roof. In my opinion, it is a standing seam metal roof (SSMR), which is ideal for both commercial and residential applications.
Standing Seam Metal Roofs
Metal standing seam roofs are lightweight (great in seismic zones), fire resistant (excellent in wildfires), impact resistant (think hail), easily engineered to withstand winds of 130 mph and more and are extremely long life. The greatest attribute of the SSMR, however, is its longevity. Recent studies indicate that Galvalume® coated steel standing seam roofs are lasting 40-60 years. This means that even if your SSMR is 15 years old, it can still outlast a PV system, eliminating the roof replacement expenses previously mentioned.
Both thin film and crystalline arrays can be installed on an SSMR without penetrating the roof.
Another valuable attribute of the SSMR is the ability to attach either the flexible thin film or the glass-based crystalline PV module to the SSMR panels without penetrating the roof or using an expensive racking system. Roof penetrations are both costly to waterproof and have the potential for leaks. Racking systems are generally required on other roof types. The material and installation costs of racking systems in addition to the penetration costs can often exceed the cost of the SSMR. In many cases, this means that by going with an SSMR in lieu of other roof types and eliminating the racking system for your PV array, you can save enough money on your PV installation cost to pay for your roof.
If you want to install a large PV array on a commercial building with a flat roof, you can often pay for a retrofit framing system with a SSMR that will far outlast other commercial roof types, increase your building energy efficiency and provide the perfect platform for you PV array.
With a multitude of benefits for a standing seam metal roof, coupled with the long term money savings of a PV array, it’s easy to see how solar and metal are truly the perfect combination.
Building owners and managers fortunate enough to have a metal roof know personally its durability, resiliency and reliability, not unlike that contributed to the U.S. Postal Service of yore: “Neither snow nor rain nor heat nor gloom of night …”—nor fire, nor hail nor the like—will prevent it from fulfilling its function. Those natural elements conspire to knock on the good reputation of a metal roof, to no avail. But how does a metal roof hold up against a more ominous threat… lightning?
