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Are You Considering Adaptation in Your Roof Design?

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Your Roof Designs Are Resilient and Sustainable – Great Job! But Are You Considering “Adaptation” in Your Planning?

In a recent article, I discussed the difference between sustainable and resilience as pertaining to low slope roofing. Both words are often considered as describing “good” attributes of roofing and are sometimes assumed to be essentially the same. There have been and continue to be industry discussions about the environment and climate change; sustainability and resilience are sometimes just assumed to address environmental and climate change concerns in ways that are “good.” But sometimes, these words are used without really appreciating whether or not they are essentially the same, different, or in some way linked.

As discussed in the article,

Sustainability is the capacity for:

  • Human health and well being
  • Economic vitality and prosperity
  • Environmental resource abundance

So, the building designer who wishes to incorporate sustainability in their material choices might ask:

  • Are materials safe for humans and the ecosystem?
  • Is this design energy and resource efficient?
  • Is a material available or will its use today cause a shortage in the future?

In short, the building designer concerned with sustainability generally asks if materials are safe, are readily available, and do no harm to the environment.

In contrast, Resilience is the capacity to:

  • Overcome unexpected problems.
  • Continue or rapidly bounce back from extreme events.
  • Prepare for and survive catastrophes.

So, key questions for the building designer are:

  • Can a structure be occupied and functional after a severe storm or some other extreme environmental event?
  • Will occupants be able to function in the absence of utilities?
  • What reduction in occupational capacity is acceptable after an extreme environmental event?

The building designer concerned about a building’s resilience wants to maintain a building’s operability and functionality as much as possible after a damaging natural event such as an extreme storm.

Could Future Extreme Weather Events Get Worse? – The Case for Adaptation

Basic physics tells us that carbon dioxide absorbs infrared energy, i.e., heat. In other words, carbon dioxide in the atmosphere is partly responsible for absorbing heat both from the sun and what is re-emitted from the earth’s surface. Actual measurements have informed us that carbon dioxide levels in the atmosphere are rising. Taken together, these two statements suggest that global temperatures are rising, something that has been experimentally observed, as shown by NASA GISS (National Aeronautics and Space Administration Goddard Institute for Space Studies) below:

Another important observation is the changing nature of the built environment. A growing percentage of the world’s population are now urban dwellers, as shown by a chart from the United Nations Population Division:

Spatial Information Management and the Current Rapid Processes of UrbanizationScientific Figure on ResearchGate. 

There are several important consequences of urbanization:

  • Food, water, and power delivery to large urban areas is very complex and disruption affects far more people, possibly in more disastrous ways, than in rural populations.
  • Urban areas are highly reliant on complex fuel, transportation and communication networks. The resilience of these networks is harder to maintain than their simpler counterparts in rural areas.
  • The urban heat island, UHI, effect is a verified phenomenon whereby urban areas are significantly warmer than surrounding areas, especially during summer periods.

As the world’s population becomes more urban, cities become more populated, increasing the UHI effect as shown in this graphic:

Courtesy of the Cooperative Institute for Meteorological Satellite Studies,
Space Science and Engineering Center (SSEC), University of Wisconsin-Madison.

UN Habitat has stated that “The effects of urbanization and climate change are converging in dangerous ways.” An example of what this could mean is shown below for New York City:

According to researchers at Columbia University and the Goddard Institute for Space Studies (GISS), while New York City experienced 7 days above 90°F in 1900, by 2080 most of the summer could be above 90°F with 17 to 50 days exceeding 95°F.

While extreme weather events can create direct challenges to the building envelope, such as high wind and flooding, there is also the indirect challenge due to electricity supply outages. Super Storm Sandy, which impacted the north-east region in the fall of 2012, not only caused significant damage to buildings, but also resulted in widespread loss of power to the New York urban region.

Electrical power outages, in turn, lead to a loss of building heat or air conditioning which can reduce or prevent functional business operations in affected buildings. Furthermore, as witnessed during the Super Storm Sandy event, elevators become inoperable, water in tall buildings ceases to flow due to pumps being inoperable, and trains and communications can be disrupted because of the lack of electricity. In short, urban regions are particularly sensitive to the loss of electricity. As can be seen in the following chart from the Energy Information Agency, significant weather-related electric grid disturbances have been increasing for many years, in tandem with increased extreme weather events.

Administration, Energy Information U. S. [data]: assembled by Evan Mills, Lawrence Berkeley National Laboratory.

Future Challenges for the Built Environment

Summarizing the challenges that might be faced by the future built environment, it would appear that:

  • Data suggests that extreme weather events are increasing. As such, buildings could be expected to face higher wind loads, greater frequency of large hail events, and flooding, amongst other challenges.
  • The built environment infrastructure might see increasing power outages, leading to significantly reduced functionality.
  • Urbanization is increasing, putting more of the built environment at risk of extreme weather events and power outages.

Adapting to Future Change

About ten years ago, it was recognized that reflective roofs are an adaptation strategy to long term global warming. Reflective roofing returns some of the sun’s energy back into space, lowering heat flux into buildings and helping to reduce the urban heat island effect. This is a strategy that will not only continue to be effective in the future but will become more important. However, while reflective roofs are now widely specified, they are still only a little more than 50% of the market for new and re-roofing projects each year.

Beyond reflective roof membranes, there are now efforts to develop membranes that not only reflect the sun’s energy but that can actively cool a roof’s surface. A little recognized fact is that reflective roofs do radiate heat back into the sky during the night, lowering the roof’s surface temperature to below that of the surrounding air. However, an Australian team at the University of Technology, Sydney, has shown that it is possible to lower a roof temperature significantly below ambient temperatures during the day, as shown in the following chart:

A. R. Gentle and G. B. Smith, A Subambient Open Roof Surface under the Mid-Summer Sun

The team’s experimental roof materials have been shown to radiate back more heat than they absorb from the sun. While this work is still in the research phase, it is a good example of how building envelope technology could adapt to changing needs. As urban heat islands become hotter, this is an example of adaptation to a roof membrane that could actively cool.

Already, in the area of improved thermal insulation, vacuum insulated panels are starting to become available. These offer a step change in the insulation value per inch (R-value per inch).

Picture credit ORNL

While true vacuum insulated panels might not be totally practical due to handling issues, researchers at the Oak Ridge National Laboratory have already improved on the concept and have prototypes of versions that show a potential for surviving the typical construction environment.

For high wind events, the means to improve wind resiliency is known; fully adhered assemblies typically have higher wind uplift resistance than mechanically attached systems. Taking this to its logical outcome, if all the layers are adhesively attached then the assembly becomes monolithic as shown in the following schematic:

By including a vapor retarder into the assembly, air movement up into the system is blocked, thereby further countering uplift forces. With only the bottom layer of insulation being mechanically fastened, the system is essentially monolithic with loads being spread across the assembly.

As discussed earlier, two major lessons from the aftermath of Super Storm Sandy were that both electric power and water were cut off for an extended period afterwards. The lack of electricity affects many things including heat and lighting. Lack of heat is best addressed by making sure that buildings are designed beyond code, which in the future could include the use of vacuum insulated panels described earlier. Lack of interior light could be addressed through greater use of passive lighting techniques. These include louvers that can direct light, light tubes, and skylights, as shown here, in the GAF World Headquarters atrium.

For water, rainwater harvesting systems are already in use in some areas of the US, for example Virginia. More widespread use of these and consideration of other approaches to capture water such as blue roof systems, with an example shown here,* would be adaptive towards future power outages.

Energy Resilience

Loss of grid electric power is a major challenge for urban infrastructure. While rooftop solar installations on commercial and industrial buildings is increasing, they do not provide power to a building in the event that the grid goes down unless supplemented with storage. When storage is added, such systems become the basis of microgrids, which are able to operate even when grid power is absent. Microgrids typically operate at the neighborhood level, but single buildings installed with solar and energy storage can operate as nanogrids.

Conclusion

As weather events become more extreme, today’s solutions for improving resiliency of the built environment may not be sufficient. Also, the growth of urban areas and increasing electric grid outages could compound the operability of commercial and industrial buildings. Fortunately, ways to improve the toughness and resiliency of roof assemblies are available today, with further possible improvements being identified. Increased use of solar power coupled with storage could ensure improved resiliency in the face of grid issues.

*Trade and company names or company products referred to herein are intended only to describe the materials and products discussed. In no case do these references imply recommendation or endorsement, nor do they imply that the particular products are the best available for the purpose discussed.



There are 14 comments

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  1. Scarlett Denton

    Hello,
    Thank you for sharing this. This Article is very useful. According to statistics, roofing is one of the most important jobs in the world. We all know the importance of having a “Roof over our heads” and we often neglect our Roof Sheeting, Skylights Accessories, and Guttering until it is too late. Since roofs are, by nature, exposed to the elements, the roofs will have to change in order to minimize the problems in different Climates. Thank you so much for sharing this blog.

    • Thomas J Taylor, PhD

      Thanks for the kind response. Yes, our climate is becoming less predictable and extreme weather events are occurring more frequently. This needs to be considered for today’s roofing designs.

  2. Julian Regina

    Dr. Taylor! You make some wonderful points! We’ve been trying to talk customers into adaptive roofing options for many years now. I feel it’s only recently that it’s taking off. I think more and more people see the benefit of having a sun light in the house for a little extra cost. The health benefits that an adaptive roof can create are very much worth the cost!
    Keep preaching the good word!

    Cheers!

    Julian

    • Thomas J Taylor, PhD

      Julian – thanks for the kind comments. Yes, as extreme weather events increase and climate becomes less predictable, we need to be thinking ahead about what tomorrow’s roof designs need to accomplish. It sounds as if you’re already on that journey. Take care, Tom

  3. Sean Chase

    Thanks for this enlightening article. We are getting more and more of hail-damaged roof repair projects than in the past years that’s why we don’t do temporary repairs but also look at the durability of the newly-paired roofs while educating our customers. This is what we tell to our customers about hail-damaged roofing so they can decide for a better roofing design or replacement:

    * When your roof sustains hail damage, it’s likely to lead to structural deterioration, which can cause nightmarish leaks into your home (and further damage to the interior).

    * A metal roof can get pretty badly dinged-up during a hail storm… but unless the hail actually penetrated the metal, however ugly it is, many insurance policies won’t cover replacement (non-penetrating dings can be considered “cosmetic”).

    * The hardest-hit part of your roof will likely be the ridge cap, which can’t be seen from the ground, and where the hail impacts the roof directly.

    * Hail will damage shingles, even if just at the edges, in a way that requires replacement.

    * Granules knocked off your “asphalt” shingles by hail stones can significantly reduce the shingles’ effectiveness… those granules help block the harsh UV rays and slow the roof’s deterioration. Any cracks caused by the hail, of course, are also highly detrimental.

    * Hail often damages only one side of a roof… especially in Colorado, where high winds often accompany hail storms. So it’s possible you don’t really need a complete roof replacement.

    • Thomas J Taylor, PhD

      Sean – you make some great comments. The article was addressing the commercial roofing side, but as you point out, the same issues face residential steep slope roofs as well. I realize you are talking about dealing with issues after a severe weather event – but when roofs get designed we need to be looking to what might happen down the road and “adapt” our designs to an evolving future.

  4. Rob Cooper

    “However, while reflective roofs are now widely specified, they are still only a little more than 50% of the market for new and re-roofing projects each year.”

    So how do we encourage more adoption at our level as the local installer? I’d love to see more of these going up, but I think we need to do a better job of educating the property owner on the long-term cost savings as well as the environmental impact of a reflective roof.

    Great article as always Thomas, thanks for sharing!

    • Thomas J Taylor, PhD

      Rob – thanks for the comments and the great question. So, why aren’t reflective roofs specified more? There could be several reasons, for example there has been modeling of energy savings done by a competitor that has claimed that absorptive roofs (i.e. non-reflective) are necessary to avoid a so-called heating penalty in the winter. Turns out, that modeling was done assuming electricity was used for heating – not a common option in the north! For a better analysis take a look at our blog on energy savings. Also, there has been misinformation about condensation risks with reflective roofs, which we have debunked here. We just have to keep plugging away at the message and continue to educate the building community. Kind regards.

  5. Geomembrane liner

    If you are dealing with roof designs, it is better to adapt it according to the kind of environment you are living in. The traditional roof designs were according to need. In hill stations, houses have sliding roofs. This adaptation can help a lot to tackle with many things. Thank you very much for sharing this!

    • Thomas J Taylor, PhD

      You are right that one needs to look closely at the local environment and adapt designs to that. However, the larger issue is that all of our environments are now changing and we need to consider what the future might bring – especially relative to extreme weather events. Thanks for checking in with us.

  6. Jakov

    Thanks for sharing this informative article! We’re glad to read that improvements are being readily and actively made/discussed. Adapting to the current global climate is something all roofers need to consider.


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