Full Cover Roofing : articles

Solar roof shingles are one of the most difficult shingles to locate today. One of the greatest benefits of solar roof shingles are they permit the house owner to have the kind of roof they want. Solar roof shingles can be utilized in a variety of ways. The kind of shingles purchased will decided by the homeowner’s taste.
 
Solar roof shingles can be manufactured by a number of different companies, but are hard to find in many retail stores.  This is because the manufacturing costs of the shingles can make the price of solar roof shingles much more expensive than some other types of roof shingles.  Many homeowners choose to order their roof shingles directly from a manufacturer instead of trying to find the one that they want located in a store nearby.

Many of the homeowners that have purchased solar roof shingles are very pleased with the way that they work.  The homes are very comfortable and the shingles are very attractive once installed on the home.  The shingles can either be installed by trained professionals or installed by the homeowner as a do it yourself project.  These shingles are easy to take care of and can be easily maintained to keep the roof shingles looking new.
 
You will want your solar roof shingles to continue to look as new as the day you installed them, regular maintenance is required to keep them in great condition. If you have to climb on roof, it is advisable not to walk on the roof too much because the weight can cause the solar roof shingles to weaken.

Is roof repair something you are going to have to deal with soon? You might want to take a look at these very useful tips. Roof repair of a flat or angled roof is not a simple task. Take notice of this relevant information.
 
Roof Repair Requires the Right Supplies On Hand
 
Before you try working on any roof you want to make sure that you have the proper roof repair supplies on hand. This is important because the last thing that you want is to get all the way up on the roof only to realize that you are missing something that you need. Now there are a few basic pieces of equipment that you almost always need when it comes to roof repair.
 

A hammer for one, which is almost always necessary, whether you are working on shingles or fixing a hole in the roof, but there are also other equipment and supplies that you will need and which are going to vary depending on what sort of job it is that you are going to be working on.
 
One of the best tips for roof repair involves chasing leaks. This is one of the most common reasons for problems on roofs and why contractors are called in to work on them. There can be many different reasons for a leak, including that there is a hole in the asphalt shingles, or that there is a hole in the top of the underlayment.
 
Chasing a leak is not always as easy as it may seem to be, and as most contractors will tell you that they have experienced. When you are working on flat or low-slope roofs, you want to make sure that you inspect any roof drains near the leak area and if you find that they are plugged or draining slowly, then they are probably the reason for the leaks.

Depending on the angle and the type of roof you are working with will determine what kind of repair will be required. It is a good idea to learn as much as possible so you can. Knowledge will also keep you and anyone else on the roof safe.

Since tin roofing material is mainly used on factories, warehouses and stores, it does not mean that it cannot be used on a home. Typically tin roofing materials are installed on commercial buildings such as factories and stores. Even though this may be the norm, it can be installed on homes. Although there are problems using tin roofing material on your home such as: 

* High Cost of Insulation
* Costly Sound Proofing
 
If you don't quite like the tin roofing material you could also use roof shingles, they are not as expensive as clay tiles, but they have their problems too as they cannot be put onto flat roofs. Even though a roof is classified, as flat it isn't really, it has to have a gradient of at least five degrees for the rain to run off towards the outside boundaries of the house.

 Council Has A Say
 
Whatever choice of material you chose, it will have to be decided on before the plans are submitted. The council will be able to tell you also if you are allowed to use tin roofing material in your area or if all have to be hidden out of eyesight from the road. Since the council does play an important roll in the choice of roofing, but there are ways to get around things at times, if your budget is limited.
 
Before you renovate your home, you should keep in mind the type of roof on your home. For example, if your home is installed with tin material and you want to use clay, you will most likely to get new trusses that can handle the extra weight. If your renovation includes adding on additional rooms, you need to find out if you have enough carrier beams to support the trusses.

Tin roofing material has to be painted regularly and or maintained, checked for leaks as the material is not as hard wearing as clay tiles. It would also be more expensive to replace a whole sheet of tin roofing material than it would having to replace one clay tile, unfortunately if you can afford to have the trusses plans changed and done to be able to put clay tiles on do so. The best part about having clay tiles on your roof is that it dramatically increases the value of your home too if you ever wish to sell.

Unfortunately time and weather will age and deteriate a roof. A roof is an important part of a building. Avoiding repairs can cost big cash. Fixing problems as soon as you find them is the best way to avoid unnecessary additional costs. Leaks cannot only damage the roof but any items you may have in the building such as costly equipment or inventory.
 
Stop Damage in its Tracks and Hire a Roofing Contractor
 
Hire a  roofing contractor before the damage gets too severe! For instance, water damage can cost your business a whole lot of money and worse; it can delay production of your products and also hamper delivery schedules. The only real problem in regard to hiring a good commercial roofing contractor is the vast numbers of them that are willing and able to do the job for you.

To ensure that you are able to pick the right  roofing contractor for you roofing problems it makes sense to first research a few prospective contractors. You need to factor in more than just the price angle and look also at their reputation, quality of work, previous works, and current workforce. This of course means spending a few hours investigating a few prospective commercial roofing contractors in detail; you should not mind these initial efforts because in the long run they will save you plenty of money, time and effort.
 
You need to also establish whether a  roofing contractor is licensed to ply their trade and for this it pays to check the local area’s building code enforcement’s professionals from who you will be able to ascertain whether a contractor is licensed or not. Next, you need to ascertain whether the contractor carries general liability as well as worker compensation insurance cover. Also, don’t forget to get the commercial roofing contractor to provide you with copies of insurance certificates as well as check with their insurance provider to verify that the policies are still in force.  

Selecting a competent residential roofing contractor is just as important as selecting a competent commercial roofing contractor. In selecting either type of contractor, it is important to do your homework. Best price does not mean best value. Choose a contractor on quality, not solely on low price.

Wouldn’t it be great if over time your roof could stay new looking? Unfortunately the rain, snow and sun can quickly fade the color of a roof. Luckily, you can lessen the damaging effects of weather on your roof with special roof cleaning products. Roof cleaning products are so efficient that they can bring back the new looking roof you once had. These helpful tips will help you restore your roof to its former new look:
 
Treat Your Roof Algae to Prevent Discoloration 
Roof algae are one of the main causes of roof discoloration. Algae spores are often carried by the wind and deposited on roofs. Once these algae spores find a good place to settle, they begin to multiply and cover a portion of your roof.
 Their presence may not be that noticeable if your roof is colored black but if your roof happens to be white or other bright colors, you are in for trouble. Black algae strain on white composite roof is a terrible site. It ruins the beauty of your roof. To get rid of the black algae stain, buy roof cleaning products and start treating your roof. No, you should not buy those strong roof cleaning chemicals. Roof algae are not really that tough to remove that you need some strong roof cleaning products to get it off your roof. Just buy one of those mild to moderate strength roof cleaning products and you will be able to solve your roof algae problems.

What if the algae come back, what should you do? Some places in the country are more prone to algae than the others. If you live in a place that is prone to algae, no doubt the algae will keep coming back to your roof. In this case, the only solution is to apply roof cleaning products on your roof at regular intervals. You may apply roof cleaning products on your roof once a year to the algae from building up on your roof.
 
You May Need to Hire a Qualified Roof Cleaner   
The only time you really need to contact a professional roof cleaner is when you do not get the desired outcome after using roof cleaning products yourself. Don’t be disappointed that you have to call a professional roof cleaner. Sometimes a professional is your best option. A professional roof cleaner will have your roof in like new condition fairly quickly.

Completed in the spring of 2008, the cool and green roof demonstration/research project of Ann Arbor, Mich.-based architecture and design firm A3C took place atop its UrbEn Retreat. The project was implemented with the assistance of Firestone Building Products and in collaboration with Prof. Moji Nawab of the University of Michigan’s Sustainable Design Research Lab. The planting of 2,500 plugs in the loose-laid portion of the green roof was completed in May 2008 with the assistance of a dozen local master gardeners.


The Subjects

The roof consists of three different types of membrane roofing. The south end and northwest corner of the roof are 60-mil black EPDM. The northeast corner of the roof is a specially coated TPO, and the center section of the roof is a green roof with a 60-mil white TPO roof membrane and a 45-mil slip sheet/root barrier. Four and a half inches of closed-cell polyurethane was installed on top of the wood decking with a top layer of a half-inch paperless gypsum product on the insulation. The combined R-value of the roof is R-30, which is 50 percent more than the current ASHRAE prescriptive requirement for the state of Michigan.

he EPDM in the northwest corner was divided into four strips. The northernmost section was left black, while the next section to the south was coated grey. The next southern section was then colored buff, while the southernmost section was coated white. The roof coating material is designed to absorb less invisible “near-infrared” radiation (NIR), creating a cooler roof with a higher solar reflectance. These cool coatings lower roof surface temperatures, reducing the need for cooling energy.

While research studies on the thermal performance of cool roofs have been done for Minnesota and Maryland, we are not aware of any done in Southeast Michigan that take into consideration the local lake-effect weather, which results in only 2.5 days of clear sky per month during a typical winter. The 2007-2008 winter was colder and snowier than our typical winters, but it also had a few more clear-sky days. It was also our intent to study the differences between cool roofs, and between cool roofs and green roofs of varying depths during a full year.

Live Roof/Hortech provided a 4-inch pre-vegetated tray system, and Xero Flor provided a 2.5-inch mat system. We worked with Jorg Breuning of Green Roof Services in the design of the extensive and semi-intensive loose-laid systems. Atwell Hicks’ William Knighton assisted with plant selection.


Data Collection

A total of eighteen sensors were installed so each area could be monitored, and each area has a primary and backup sensor. Sensors are installed just under the membrane, just above the deck and just below the roof structure within the conditioned space. Data is collected at 4-minute intervals. This data is regularly downloaded and converted to spreadsheets to allow both numerical and graphical comparison. (See Figures 1 and 2.)

Data from the first day of summer 2008 showed the outdoor temperature went from 60 degrees in the early morning to 75 degrees during the afternoon. It was a partly cloudy day, as evidenced by the spikes in the temperature. During that time, the temperature under the black roof membrane added 23 degrees of additional heat versus the outdoor temperature, going from 60 degrees to 98 degrees. The grey and buff roofs had temperature highs of 85 and 80 degrees. The white roof reduced the thermal load to basically the outdoor temperature, resulting in only a 5-degree rise in temperature.

Under the shallow green roof adjacent to the cool roof strips, the temperature went from 60 to 68 degrees — never adding a thermal load at all. It actually helped keep the building cool. Similar results were seen in spring and fall as well. The winter chart shows that the green roof did help keep the roof warmer than the cool roof. This is probably in part due to the snow, which accumulates on the roof and the green roof acts as a thermal mass between the snow and the roof membrane.


Results

After a full year of recording the performances of the different cool roofs and different-depth green roofs, we found that the green roofs performed better than the white cool roof with regard to cooling. But because of the amount of insulation, the thermal load due to the roof was negligible between the cool white roof and the green roof. That said, we would always recommend a green roof if budget or structure allowed. Green roofs provide a wider range of benefits beyond thermal performance — including stormwater runoff quality and quantity, and extending the life expectancy of the membrane roof — as well as intangibles like aesthetics. Green roofs can also act as a desirable gathering spot, especially if you have a gathering/meeting spot overlooking the park-like green roof as we do in the UrbEn Retreat.

As green building strategies evolve to keep up with increasingly stringent building energy codes and standards, so do cool roofs. A roof, as any other building component, can be selected to best serve a particular purpose, such as weather resistance or thermal regulation. Cool roofs are optimally designed to minimize the transfer of heat from the sun to the interior of a building.

A cool roof is defined by the radiative properties of the roof’s outer layer, or more specifically, by its solar reflectance and thermal emittance properties. Solar reflectance is a measure of the portion of initial solar radiation that is immediately reflected off the roof surface back in the atmosphere without heating the roof itself. Thermal emittance is a measure of the solar energy that the roof re-emits, or re-releases into the atmosphere as infrared light, after being initially absorbed. The remainder of the solar energy, that which is neither reflected nor re-emitted, is transferred to the building as heat or is convected by ambient breezes into the surrounding atmosphere, heating the surrounding air. The amount of solar energy transferred to a building can therefore be influenced by the roof design and construction. (See Figure 1.)

Thanks to advances in materials technology, white roofs are no longer the only type of cool roof available. Cool color pigments have been developed to efficiently reflect solar energy (light) in the Near Infrared (NIR) spectrum, whereas standard colors tend to absorb NIR energy. The NIR spectrum is invisible to the human eye, so two seemingly identical colors in the visible spectrum can perform differently in the NIR spectrum. With vast color and material choices, selecting an aesthetically pleasing roof design while maintaining cool roof performance is now possible.


Beyond Energy Bills

In addition to reduced building energy consumption from diminished air conditioning requirements, cool roofs have numerous indirect benefits, including cutting greenhouse gas emissions, alleviating the urban heat island effect, reducing smog, as well as various public health benefits.

Cool roofs reduce greenhouse gas emissions by conserving electricity and reducing power plant production demand incurred from air conditioning use. Creating electricity not only wastes a great deal of energy in the conversion process, but also produces CO2, particulate matter and other air pollutants.

Cities can be 2 degrees to 8 degrees warmer than surrounding environments due to the large areas of dark surfaces, consisting mainly of roads, parking lots and dark-colored roofs. The extra heat absorbed through dark surfaces during the day is convected away by ambient breezes, raising air temperature averages; this phenomenon is referred to as the urban heat island effect. Cool roofs help mitigate the intensity of the urban heat island effect by reducing heat absorption and transfer to the surrounding air.

Lower ambient air temperatures resulting from cool roof applications also reduce the production of smog, a process accelerated by warmer temperatures. Reduced greenhouse gas emissions and smog production benefit public health by reducing the prevalence of asthma and other respiratory health conditions aggravated by air pollution.


Codes and Programs

As building technologies improve, building codes and programs have evolved to enforce strategic green building design and construction practices. The following section provides an overview of some cool roofing codes, green building programs, rebate programs and tax credits. For more information, please visit www.coolroofs.org.

Two primary organizations, the International Code Council (ICC) and the American Society of Heating and Air- Conditioning Engineers (ASHRAE), have developed National Model Energy Codes. These codes are not mandatory or enforceable until a jurisdiction adopts the documents as part of regulation or law. In the United States, many states and jurisdictions have adopted these codes, while others like California have developed their own.

Cool Roofs in Energy Codes: California’s Title 24, The California Energy Commission’s Building Energy Efficiency Standard, includes a cool roof prescriptive requirement. A new version goes into effect on Jan. 1, 2010. It includes prescriptive requirements for low-slope and steep-slope roofs and for residential and non-residential building applications. The table in Figure 2 provides a brief overview of Title 24 requirements, but please note that there are many exceptions. For more information, please visit www.coolroofs.org or the California Energy Commissions Title 24 Web site, www.energy.ca.gov/title24/.

Green Building Programs: In 2009, the U.S. Green Building Council updated their Leadership in Energy and Environmental Design (LEED) program. LEED 2009 includes several structural changes to the rating program as well as changes to individual credits. LEED 2009 includes new point allocations for the various credits. There are now a total of 100 possible points for a given project (as opposed to the 69 points possible in previous versions). The cool roofing credit is still worth a single point and is available for every LEED program offered, including LEED for Schools, LEED for Existing Buildings, LEED for Core and Shell, and LEED for Homes.

Rebate Programs: As the green building movement sweeps the country, more utilities across the United States are providing incentives for cool roofs. States with current utility rebate programs include Arizona, California, North Carolina, South Carolina, Colorado, Florida, Idaho, New Jersey, New York and Texas. Please check with your local utility company if they have a cool roof rebate program in your area.

Rating Programs: The Cool Roof Rating Council (CRRC), an independent nonprofit organization that has developed and administers a third party rating system for the radiative properties of roofing materials, provides unbiased and credible ratings that are available online in the Rated Products Directory (www.coolroofs.org/products/search.php).

The CRRC does not set minimum requirements for solar reflectance and thermal emittance. It is up to the code bodies, green building programs, and utilities to set and define cool roof minimum radiative property requirements. The U.S. Environmental Protection Agency’s ENERGY STAR hosts a Reflective Roof Program that provides an ENERGY STAR label recognized by consumers as an indication of energy-efficiency.

Manufacturers can choose to rate their products with ENERGY STAR as long as they meet ENERGY STAR’s minimum specifications. (See Figure 3.)

Tax Credits: Through Dec. 31, 2010 the IRS will provide a tax credit for ENERGY STAR metal and asphalt roofing products. The tax credit is for 30 percent of the cost of the roof, up to $1,500. Please visit the ENERGY STAR Web site (www.energystar.gov) for details on how to receive a rebate.



CRRC as a Resource

CRRC ratings include both initial and three-year aged ratings for solar reflectance and thermal emittance. For three years, the roofing material is exposed to natural weathering conditions on three test farms representing three key climate zones (hot/dry, hot/humid, and cold/temperate) to determine aged product performance. The CRRC also has a mandatory random testing program for all rated products in the directory to ensure accurately reported ratings. Currently, there are over 1,390 rated products in the directory.

Nationally recognized, CRRC ratings are often either required or recommended to meet cool roofing standards for building codes and programs.

California’s Title 24 requires CRRC ratings, while other jurisdictions including Austin, Dallas, Houston, Chicago and the state of Florida have cool roof building codes with minimum radiative properties that reference the CRRC. Both draft ASHRAE Standard 189.1 and LEED 2009 now reference the CRRC.

Advances in technology now allow cool roofs to come in a variety of colors and materials, no longer limiting aesthetic and architectural design preferences. Suppliers, manufacturers, and architects using the CRRC directory and educational resources now have access to a wealth of product information that can make cool roofs a viable option for achieving a green building vision. Therefore, when looking for an effective energy saving building strategy, consider a cool roof.

New Jersey’s Atlantic City Convention Center is the largest single roof-mounted, grid-connected solar system in the United States. At almost 500,000 square feet, the project is a huge investment for the city, which wasn’t about to gamble on its new roof. Facility managers wisely chose to enhance their energy saving investment with a durable and highly reflective TPO (thermoplastic polyolefin) roof membrane.

Reflective roofs like TPO can enhance the energy efficiency of solar roofing systems by up to 20 percent by reducing rooftop temperatures. In addition, GAF’s Freedom™ TPO is self-adhered and does not require the use of solvent-based adhesives or hot asphalt, making the Atlantic City project that much “greener.”

The convention center roof is also unusual in that most solar installations require that the existing roof be torn off. However, that wasn’t an option in Atlantic City. The dynamics of the convention center roof and the extra cost of a tear-off would have put the project way over budget.

The existing roof, a 12-year-old granular surfaced modified bitumen also manufactured by GAF, was performing well and subject to yearly evaluation and maintenance. However, at some point during the 20-year life of the solar system, this roof would have to go.

“We explained that the convention center would be responsible for a very difficult tear-off sometime in the future,” said Herb VanGent, eastern area manager of field operations for GAF. “To its credit, the facilities team chose to recover with the reflective TPO membrane.”

In addition, there were concerns about the effects of a tear-off on the building’s lightweight concrete deck. “If we tore off the modified bitumen, we would have disturbed or damaged the underlying deck,” said Frank Moore, AIA and president of roof consulting firm ARMM Associates Inc., Cherry Hill, N.J. “Fortunately, we found that the building was easily able to handle the additional weight of a second roof system and the solar panels.”


Installing the New Membrane

Thomas Company Inc., a full-service roofing and sheet metal contractor based in Atlantic City, was chosen to install the new membrane. Roofing crews first power washed the surface of the modified bitumen roof and secured a 3/8-inch gypsum cover board over the existing membrane with Olybond500 insulation adhesive.

OlyBond500 is a dual-component, low-rise polyurethane foam adhesive manufactured by OMG Roofing Products of Agawam, Mass. It is designed to attach insulation to roof decks without noxious odors that may disturb building occupants. The foam is also low in VOC content and meets Factory Mutual (FM) I-90 wind uplift standards required by the State of New Jersey for the convention center project. In addition, GAF-supplied Drill-Tec Impact Locking Nails used to enhance wind resistance around the perimeter of the roof.

“Thomas Company did a great job installing the Freedom TPO membrane,” said Moore. “There wasn’t even one blister or lump in almost 500,000 square feet of new roofing, and the GAF membrane went down very smoothly. We also found that the TPO membrane and cover board were adequate to handle the additional roof traffic and maintenance required for the solar system.”

After the membrane was adhered to the gypsum cover board, Pepco Energy Services of Arlington, Va., installed nearly 13,500 monocrystalline solar panels, covering almost 85 percent of the 480,000-square-foot roof.

The solar system required several thousand penetrations through the new TPO membrane. Initially, engineers considered caulking the penetrations, but again the convention center made a safer bet. It allowed GAF to provide custom-made TPO flashings for all the penetrations.

“We really felt the custom-made flashings were needed to provide longevity for this roof,” VanGent said. “Also, these details were required for our 20-year, NDL warranty.”

Architect Moore was also concerned about the wind resistance of the panels themselves. His firm helped design a four-bolt system for attaching the solar panels into the lightweight concrete deck. The resulting detail offered 4,000 pounds of pullout resistance per panel and a watertight seal for the TPO membrane.

Moore also questioned the impact resistance of the panels to debris from seagulls at the seaside location. “We needed to ensure that the panels, which are angled at 12 to 15 degrees, would hold up to strikes from anything dropped by gulls or other shore birds. We found that the panels were up to the task and able to sustain these impacts.”

Today, the 2.37-megawatt rooftop solar power system produces up to 26 percent of the convention center’s annual electricity requirements.

“Since the roof was going to house a solar array system, the owners wanted a white, reflective roofing system which would help to minimize rooftop temperatures for better performance of the solar panels,” said Jim Hagel Jr., senior project manager and estimator with Thomas Company.

Thomas’ roofing crews also did their part by adhering to a tough deadline. Roofing work started at the end of July 2008 and needed to be completed before freezing temperatures set in. Thomas had the roof membrane installed by Nov. 1, effectively beating an early New Jersey winter by a nose.

“We were very pleased to be involved with this historic project. You don’t get the opportunity to install a roof of this magnitude or importance very often, so when they come along, they are always special.”

Common sense tells us that a low-slope reflective roofing system should improve a building’s energy efficiency and save money on energy costs versus a black roof. After all, in full sun, the surface of a black roof may experience a temperature rise of as much as 90 degrees Fahrenheit, reaching mid-day temperatures of 150-190 degrees. A white reflective roof typically increases only 10 to 25 degrees above ambient temperature under the same conditions.

But how can you get a quantitative analysis of the potential energy savings for your building without performing a detailed building energy simulation? Simpler Web-based tools exist that can help architects, specifiers, roofing contractors, building owners or facility managers assign an estimated value on the annual energy savings that can accrue during the life of a typical commercial white reflective roof versus a non-reflective black roof.

ENERGY STAR’s Roofing Comparison Calculator is one such tool, equipped with a user-friendly functionality that anyone on the building team can use with ease. Developed by the U.S. Environmental Protection Agency as part of its mission to accelerate the market penetration of energy-efficient building technologies, the calculator analyzes several key variables, and is a highly recommended exercise when contemplating a change from a black roof system to an ENERGY STAR-rated white one, or determining the savings when considering among alternatives on a new building.

The calculator automatically balances cooling savings from a light-colored roof with minor increases in heating costs — sometimes referred to as the heating penalty — that could accrue by not having a dark roof in the winter. (Many buildings with black roofs have de facto white roofs at least part of the winter due to snow cover.)

Savings from installing ENERGY STAR-labeled roof products will depend on the geographic location and climate where it is installed, existing insulation levels in the building, the type of roof it replaces, the type of roof installed, and how efficient the HVAC system is. Roofs that are lightly insulated, i.e., roofs with 1 inch of insulation or less, will see the greatest savings. The following inputs are evaluated:

• Building Details — The building’s age, use and number of days of operation per week.

• HVAC — Efficiency ratings of the building’s HVAC system, factoring in the system’s age and rigor with which it is maintained; use of ENERGY STAR-labeled products can be noted. With many air conditioning units already absorbing massive amounts of solar energy from rooftop locations, a surrounding cool roof can do much to reduce the strain on the system over time.

• Roof Details — R-value of the insulation; solar reflectance value of the existing dark roof; that same value for the reflective material being considered, and the square footage of the air-conditioned roof area.

• Energy Prices — Electricity/natural gas costs for the area; if this data is not at hand, the U.S. Energy Information Administration (www.eia.doe.gov) generates average energy prices by state.

• Building Location — City and state only; needed to generate cooling and heating degree day calculations from the nearest National Weather Service facility. These indices express the difference between a reference value of a comfortable 65° F/18° C and the average outside temperature, leading to the number of “degree days” the temperature variations are likely to result in heating or air conditioning decisions.

The heating and cooling degree day information generated from this exercise can be moved into other calculators for insulation, which are also available online. ASHRAE 90.1, the national model energy code for commercial buildings, sets forth the degree to which a project’s insulation may be reduced (by climate zone) if a cool roof is installed.

It’s hard to ignore year-after-year energy savings on a roof system that will be a part of your building for many years. ENERGY STAR-rated cool roofing systems are an easy choice to save on cooling costs and reduce energy consumption.

Few people doubt the value of using sunscreen to protect against sunburns and skin-damaging ultraviolet rays. Now a wide range of products are available that essentially act as sunscreens for roofing systems. As legislators, architects and building owners embrace the idea that building design has a huge impact on energy consumption and sustainability, increasingly they are recognizing that white coatings offer big benefits with few drawbacks.

A white coating consists of a binder (usually an organic polymer or silicone polymer) that is blended with pigments and other additives that provide several benefits. First, white coatings protect roof membranes with a chemical barrier and reflect sunlight, contributing to longer roof life cycles. The second benefit, of course, is that the reflection of solar radiation can result in significantly lower air conditioning costs.


California Leads the Way

California is noted for taking the lead in environmental legislation, particularly in clean air and energy conservation. Recent legislation in California underscores the merits of using white coatings on commercial buildings to reduce energy costs. California Title 24 legislation is exemplary for its support of white coatings. Exempting buildings with high-reflectance roofing from energy audits makes sense because white coatings dramatically decrease the need for insulation and air conditioning.

Alleviating solar heating loads directly affects peak electricity requirements. Peak electric loads are often the basis for the price of electricity because they establish the energy generating needs of a region.

California Title 24 legislation requires a detailed energy audit on a new building, to show that solar heat is dissipated or removed in an energy efficient manner, e.g., through insulation and climate control systems, unless the building uses highly reflective roofing with reflectance values above 0.70. Hence, Title 24 sends a strong message to building designers: The best way to cool a building is to divert the solar energy before it raises temperatures.


Longevity Is Important, Too

California lawmakers deserve applause for encouraging the use of white coatings to reduce energy costs. But lower energy use is not the only benefit that accrues from the use of white coatings. White coatings can extend the life expectancy of many different types of commercial roofing systems simply by avoiding the high roof temperatures associated with exposure to the sun.

The technical term for exposure is “insolation,” and it is measured in terms of the rate of solar radiation received per unit area (typically expressed in Watts per square meter). Under very clear skies, up to 1,220 W/m2 of solar radiation reaches the rooftop. Imagine ordinary household hair dryers every 10 feet in both directions of a two-dimensional array: that is the intensity of the sun’s energy incident upon a rooftop. Heavily insulated roof systems block this heat from penetrating the building as heat; however, in summer months, convective heat transfer to the surrounding air and radiant heat transfer are inefficient. Consequently, the heat has nowhere to go and roofing membrane temperatures can soar.

For commercial roofing systems made from organic materials, high temperatures can shorten the life of the roofing system. Rubber as well as other synthetic polymers and especially asphalt, is susceptible to damage at these elevated temperatures. Roof temperatures can rise above ambient air temperatures by as much as 90°F. Meanwhile, the rate of degradation of the roofing materials begins to accelerate at modestly elevated temperatures, for example at 140°F. Significant damage can begin to occur at these elevated temperatures, causing both short-term and long-term performance issues.

As temperatures rise to the peak of this range, degradation of roofing systems increases exponentially. Lighter and hence more volatile organic compounds may evaporate into the atmosphere, and chemical reaction rates with water, oxygen and contaminants also increase. As a result, roof life expectancies are shortened. A rule of thumb for thermal aging is that service life is cut in half for every 18°F increase in temperature (weighted and averaged over time).

Most people appreciate that white coatings result in savings on cooling costs, but enhanced roof longevity, especially in northern states, can be another major benefit that results in at least as much savings. Without white coatings, roof temperatures can skyrocket in the summer months, especially for buildings in northern climates, because they typically have a lot of insulation to help keep in the heat during the winter months.

The inverse correlation between insulation thickness and roof life is well documented by roof asset management firms. Since ripping out the insulation every summer is of course impractical, white coatings are one of the best means available to counteract the deleterious effects of high heat levels and enhance the prospects for a long-lasting roofing system.


The Future Is Now

Reflectance is measured according to strict standards. A perfect reflector would have a value of 100 percent for all wavelengths of light; when just one value of reflectance is given, it usually represents an average value weighted according to intensity across the solar spectrum.

With the growing recognition of reflectance as an important design parameter, reflectance values are being thoroughly measured across the entire solar spectrum (including infrared wavelengths) and accurate values for specific materials and coatings are becoming readily available.

The beauty of a white coating is that the pigments, such as zinc oxide (ZnO) or titanium dioxide (TiO2), scatter a large fraction of the incident photons back into the sky, optimized for reflection in the visible and near- infrared bands. Metal-oxide pigments used in white coatings scatter light by the same mechanism that light is scattered with by the water droplets in a cloud, or fog; the scattering is due to the tiny particle size. Except for the small particle size, these materials would be transparent to light, because the metal atoms are oxidized, i.e., the valence electrons of the metals are held by the oxygen and do not interact with the incoming photons.

Most white coatings have a very high reflectance across all visible wavelengths and also have a high reflectance for near-infrared radiation (NIR). Typical reflectance values averaged over these wavelengths are in the neighborhood of 70 percent or 80 percent.