The greenest roof is improving the one you already have
By Jennie Morton | View the original article here
An existing roof doesn’t need solar panels, vegetation, or a certain membrane color to be environmentally friendly. A truly sustainable roof has the best possible performance for the longest period of time.
“Thermal properties and service life are key attributes for a sustainable roof system,” says Jim Kirby, vice president of sustainability for the Center for Environmental Innovation in Roofing. “These directly affect energy efficiency and longevity. Fewer replacements are better from a material, energy, and waste perspective.”
Poor drainage, deferred maintenance, and infiltration issues can cut your roof’s service life in half and significantly increase your energy bill. Stay on top of repairs and strategic improvements to extend the life of your roof, avoid unnecessary replacements, alleviate grid demand, and conserve resources.
Perform Preventive Maintenance
The best way to extend your roof life is to keep its condition in good shape. “With routine inspections and repairs, you can easily get 20 years or more out of your roof,” says Ted Michelsen, president of Michelsen Technologies, a roof consulting firm. “But if you defer maintenance, your roof’s life could drop to only 10 to 15 years.”
Let’s say your building is expected to last 80 years. With good maintenance, you will have three roof replacements. But if the service life is shortened to 15 years, you will end up reroofing five times during the same period – a 40% increase in replacement costs over the building’s life simply because you’ve been lax about upkeep.
Roof construction can have serious environmental impacts as well. Excess replacements consume raw materials that could be conserved otherwise, thereby increasing your carbon footprint. Each premature demolition also adds thousands of pounds of bulky, potentially hazardous waste to landfills. Reports vary by region, but construction and demolition materials can account for up to 36% of solid municipal waste, finds the EPA. And not all roofing materials can be salvaged through recycling programs.
Durable roofs keep their integrity through routine repairs. These yearly maintenance costs pale in comparison to the price of a replacement – a matter of investing pennies vs. wasting dollars.
“Annual maintenance costs are about 1% of the cost of new roof,” Michelsen estimates. “You could be spending 10 cents per square foot on yearly upkeep rather than $10 per square foot for a replacement.”
Regardless of system type, any maintainable roof should have proper drainage, good access, control of rooftop traffic, and a design that enables repairs, says Michelsen. It should also have supporting documentation whenever possible, such as original design specs, a complete leak and repair history, and the warranty.
A proactive maintenance plan includes ongoing inspections to evaluate the roof’s condition. The purpose of these assessments is to uncover failure conditions and repair them before they become a reality, Michelsen explains. You should also evaluate existing repairs to ensure the fix hasn’t lost its viability. A good rule of thumb is to inspect twice a year, such as before and after winter, as well as after major storms.
You should also look for damage whenever there’s been work done on rooftop equipment, he adds. Contractors may inadvertently cause damage by leaving debris, such as leftover screws and nails. Poor detailing from installation or repair work may also compromise the assembly, and even heavy foot traffic can result in wear and tear.
Other issues to look for include holes, flashing defects, animal activity, and organic debris such as leaves and sticks. If your roof is on a newly acquired property, make sure to evaluate existing repair work. If your maintenance history is incomplete, be on the lookout for temporary patches or evidence of former repairs.
You may also encounter damages that are specific to your roof type:
BUR – Blisters are common in these systems and can’t be ignored as they only worsen over time. Displaced or damaged surfacing may also occur.
Modified Bitumen – These roofs also suffer from blisters. This issue is often seen in pre-2004 roofs, says Michelsen, because manufacturers at the time weren’t recommending high enough temperatures to achieve a good bond. If they lack proper surfacing or the surface layer has been worn away, the membranes could become exposed.
Single Plies – Look for open seams, displaced ballast materials, splits, or cuts. You may also find surface damage caused by UV degradation. Raised fasteners are another issue. Causing the membrane to be worn away by foot traffic or working their way loose, they can penetrate through the membrane.
Metal Roofs – These systems are subject to seams popping open as well as backing out fasteners. For those with a galvanized finish, corrosion can be a big problem, cautions Michelsen. The condensate from copper coils rapidly strips off the finish, leaving the steel exposed and prone to rusting quickly. Adequate piping is needed to carry away air conditioner condensate.
Ballasted Roofs – Ballast holds the roof down and protects against wind movement, but it’s not uncommon for it to shift over time. It’s important to have ballast in its proper place so the roof maintains even loads, Michelsen notes. Otherwise the system is at risk of collapsing if the ballast drifts to one spot and the load weight exceeds structural capacity. PageBreak
As repairs are called to your attention, it’s critical to address them in an appropriate time frame. Sitting idly on an active repair or corrective measure only leads to deferred maintenance and more costly problems down the road. Any leaks or defects allowing water into the building should be addressed immediately, stresses Michelsen. If you find a vulnerability that has the potential to fail or cause a leak before the next inspection, take care of it within six months to a year. Flaws that aren’t leaking but are too difficult or expensive to fix, such as ponding water or slope issues, should be reserved for when you reroof.
Repairs should also take precedence over patches, which are only temporary measures that don’t address the root issue. Duct tape, for example, can help stop an immediate leak in a membrane tear, but it certainly won’t keep water at bay permanently.
“Repairs, however, remove wet and damaged materials and ultimately restore the roof to its original condition,” Michelsen says. “Depending on the type of defect, you may make a corrective repair to prevent a vulnerability from reoccurring or improve a defect to prevent a future failure.”
These proactive approaches can include adding water barriers under expansion joints or two-part counterflashing. If drainage is an issue, modifications may be necessary for piping. Equipment supports should also provide enough space for repairs and inspections, notes Michel-sen. A proper flashing job, for example, should have penetrations that are spaced apart by at least 12 inches.
Also be conscious of your warranty, which may limit who is allowed to perform repair work. It can also restrict what revisions are permitted on the system in the first place. Even if your proposed repair qualifies under the warranty, make sure you are able to provide proof of maintenance to maintain your coverage.
Conduct Leak Testing
The source of leaks is one of the most difficult issues to track down. Moisture intrusion can occur on an ongoing basis without any visual clues until a major failure occurs, such as the classic case of water pouring on an employee’s desk.
The pathway of the leak can also be challenging to establish without tearing into the roof itself. And as moisture seeps into the building, it comes in contact with wood, steel, and other materials, resulting in damage that can compromise structural integrity.
“Ponding water can also pose a real problem, as sunlight hitting the standing water can degrade the membrane,” explains Kirby. “Getting moisture off your roof is fundamental to the longevity of your membrane.”
In addition to regular roof assessments, leak inspections are a valuable way to address this vulnerability. These inspections should be done whenever water infiltration has occurred or soft areas in the membrane appear, says Matt McElvogue, P.E., associate principal for Building Exterior Solutions (BES), a building envelope consulting firm. The goal is to determine the source of the water infiltration, how much propagation has occurred through the roof system, and whether penetration has reached into the deck or compromised any other structural components.
“Even if there isn’t any evidence of water issues, a leak inspection should be conducted every five years as a precaution and after any storm damage that may have caused or worsened leaks,” recommends Russ Raymond, associate principal and registered roof consultant with BES.
Roof replacements are also the perfect time to schedule a leak inspection, he adds, particularly as some testing can be done more easily when parts of the assembly are exposed. It’s an opportunity to uncover hidden moisture issues or take the time to address existing ones. Otherwise you could be covering up problems that may shorten the life of your new roof down the road.
Due to the technical nature of leak testing (see sidebar at left), these inspections are typically performed by a contractor, consultant, or even your roof system manufacturer. To support the process, be prepared to provide supporting documentation of the roof’s past and current condition. Records should include repair history, inspection data, tenant complaints, and overall property condition assessments. Particularly with warranties, this evidence will help you prove that the roof has been maintained according to the manufacturer’s guidelines.
“Any leak reports that facility managers collect are also valuable,” McElvogue notes. “We can often correlate those to weather reports and see what kind of conditions occurred when a leak started. Some leaks only occur in certain instances, such as when wind is blowing one direction or if there’s ponding or wind-blown rain.”
If the leak inspection hasn’t been conducted properly or thoroughly, however, you could be pushed into a premature reroof. Unless you have a catastrophic failure, there are many repair options for leaks that will restore the roof’s integrity.
“Our philosophy is to preserve as much of the existing roof as possible. Don’t be pressured into an unnecessary roof replacement when there’s plenty of undamaged assembly that could be reused,” cautions Raymond. “Retrofits such as coatings, liquid flashings, overlays, and one-way venting allow wet or damaged materials to be resurfaced instead of replaced.”
Such was the case for a recent roof renovation of a hospital building in Texas, which had a modified bitumen roof over a concrete deck. During the renovation, it was discovered that moisture coming through the roof deck was causing blistering and delamination. Other parties involved with the project recommended full replacement, but Raymond’s firm found that the roof could be salvaged with a venting system.PageBreak
This was determined by using an IR survey to detect moisture content. The test cuts also revealed delamination between plies, as well as between plies and the cover board. Only isolated moisture was detected during plastic sheet tests.
The venting system was mechanically attached to the structural deck through installed base and cap sheet. New plies were mopped and a cap sheet with limited vents was installed. The solution preserved the existing assembly while allowing the blisters to be repaired and trapped moisture to release over time. The owner was also able to avoid replacement costs, as well as the associated demolition waste.
Insulate for Energy Savings
While maintenance preserves the existing condition of your roof, you may need to take additional measures to improve its thermal performance if it’s subpar to begin with.
According to Kirby, the ideal installation includes a double layer of insulation with adhesive or fastener attachment of the bottom-most layer. If your roof wasn’t designed with this in mind, there are a variety of retrofit opportunities to increase your roof’s R-value.
“Insulation is the main driver of efficiency in roofs and ultimately trumps roof color,” Kirby says. “Once you have the right amount of insulation, roof color doesn’t have much impact on internal energy use.”
He uses the analogy of winter coat colors. A thin black jacket may absorb a little solar heat but still lacks adequate insulation to keep you warm. Conversely, a well-insulated white coat won’t absorb much sunlight but will nonetheless keep the cold at bay. If both jackets are properly insulated, however, the color will have little bearing on comfort.
When evaluating the thermal performance of your roof, look for areas that enable heat transfer through convection or conduction. Metal fasteners and gaps larger than a quarter inch in board joints are common culprits that reduce insulation value. To minimize thermal bridging, use non-metal fastener plates.
“You can also install a cover board over fasteners. It doesn’t provide much insulation, but it will separate the metal fastener from the underside of the membrane,” Kirby explains. “Spray foam insulation is another option that eliminates fasteners altogether.”
Air infiltration can also wreak havoc on your energy consumption because it’s laden with moisture that carries heat energy.
“Air leakage is as important to thermal resistance as insulation,” notes Kirby. “Air infiltration and exfiltration make up 25 to 40% of total heat loss in a building in a cold climate and 10 to 15% of total heat gain in a hot climate.”
Adding air barriers along penetrations and transition locations can help both thermal and moisture issues. It’s also important to adjust your ventilation system after sealing measures to avoid sick building syndrome or any other ventilation issues. You can even use a blower door test to determine if the building meets code requirements for tightness.
“The insulation layer should be designed as a system and account for skylights, drain sumps, roof hatches, and HVAC units,” Kirby stresses. “The mechanical system in the building should be sized appropriately based on the roof’s actual R-value. This is critical because mechanical systems are designed based on the expected thermal resistance of the envelope. If it’s less than anticipated, then equipment could be undersized and subsequently stressed.”
Keep in mind that commercial buildings consume approximately 20% of all energy in the U.S. As heating and cooling remain the top drivers of energy efficiency, the roof can make or break your thermal performance.
“There are roughly 2.5 billion square feet of roof replacements each year,” says Kirby. “By increasing the energy efficiency of roofs to current code-mandated levels, we could potentially save over 700 trillion BTUs in energy.”
Jennie Morton is senior editor of BUILDINGS.
Earn Points for Your Roof
Are you considering green certification? Beyond obvious roof credits like heat island effect, there are many other creative ways to secure points with your roof system while improving energy efficiency and reducing environmental impacts.
Living Building Challenge
Under this certification, the roof is considered a holistic opportunity to improve building performance. These credits fall under renewable energy (rooftop solar panels or wind turbines), net-zero energy (daylighting, thermal performance), and water conservation (rainwater harvesting). It also rewards efforts to address chemicals of concern, material sourcing, embodied carbon footprint, waste management (construction and demolition waste), and beauty (such as a vegetated roof).
This program offers roofing-related credits for heat island effect, energy performance, renewable energy, construction waste management, and materials reuse. With the right system, you may also be able to make the case for recycled content, stormwater management, VOC limits, daylighting, and thermal comfort.
This rating system offers criteria for energy performance, renewable energy integration, watershed features, low-impact materials and systems, heat island effect, daylighting, minimal consumption of resources (reuse of existing buildings), material durability and disassembly, waste management, thermal comfort, and air and vapor barriers.
This certification is focused solely on roofs. It places a heavy emphasis on energy management, such as high R-values, thermal practices, durable insulation, hygrothermal properties, roof surface thermal contribution, and air barriers. It also looks at energy systems such as solar and wind turbines, as well as daylighting opportunities. Another key component is durability and maintenance, including drainage and moisture management, traffic protection, wind uplift resistance, and installation quality.
Leak Testing Methods
On your own, leaks can be difficult to fully explore. You may see ponding water or have a drip on an employee’s desk, but tracking down the path of moisture intrusion through the assembly requires expert help. A contractor or consultant may use the following methods to test for leaks.
Destructive – Takes apart portions of the roof system to see how it is constructed and what its current condition is. Like removing drywall to find a leak or mold, it is sometimes necessary to physically confirm moisture intrusion through sight and touch. This is typically reserved for small areas of the roof or cores and is one of the more expensive analysis options.
Non-Destructive – Looks at water signatures using indirect methods, including thermal imaging, radio frequency/dielectric, electrical potential/resistance, and nuclear/radioactive. These options provide a visible or audible indication of suspect areas and some can cover large sections of the roof. While the nature of this testing generally avoids damage to the roof, it also limits how far into the assembly problems can be detected.
Direct (Water Testing) – Replicates leak conditions by spraying water on suspect areas, which provides direct feedback about leak sources. Watching water interact with drains, flashing, and expansion joints can provide valuable clues. Infiltrating water, however, can cause disruptions and further damage.
Matt McElvogue and Russ Raymond, Roof Moisture Surveys and Leak Investigation