Code Requirements for Cool Roofs with Climate Zone Specifics

There is still a lot of discussion—some agreeable and some not so agreeable—about the necessary color of our rooftops.  One side of the discussion revolves around keeping the surfaces of our built environment “cool,” so there’s a movement to make all rooftops “cool” by making them white, or at least light-colored.  Those on the other side of the discussion claim that cool roofs are necessary to reduce a building’s energy use.  Cool roofs can be a really good idea, but let’s not mix up the reasons why cool roofs matter—are we cooling the urban areas (that is, reducing urban heat islands), or are we saving energy costs for individual buildings? Cool Roofs
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The average building height in the United States is less than two stories, but “white roofs” are mostly desired in dense, urban areas…and how many buildings here are less than two stories?  Tall buildings are typically found in dense, urban areas, with shorter buildings dominating the fringe urban areas.  In the suburbs and rural areas, one- and two-story buildings are more the norm.  So we have a mix of building heights in the United States, but the conflict is that the “cool roof” focus is often where the tallest buildings exist.

And unfortunately, a cool roof on a 20-story building isn’t going to reduce its energy use, especially if the code-required amount of insulation exists on that roof.  Rather, reducing energy use of a 20-story building hinges on the energy efficiency of the 20-story-tall walls—R-value of walls, percentage of windows, and solar blocking eaves, just to name a few items.  Conversely, the energy efficiency of a one-story big-box store comes down to its roof.  And for these buildings, roof color definitely can make a difference.  However, our building codes don’t differentiate based on building proportions, but only on geographic location—and that’s problematic.  But as designers, we can improve on the code requirements.

The 2015 International Energy Conservation Code provides specific information about cool roofs, which are required to be installed in Climate Zones 1, 2, and 3 on low-slope roofs (<2:12) directly above cooled conditioned spaces.  There are two ways to prescriptively comply with this requirement: use roofs that have a 3-year-aged solar reflectance of 0.55 and a 3-year-aged emittance of 0.75.   Notice that initial (i.e., new) reflectance and emittance are not specified; long-term values are more important.  The second method to comply is to have a 3-year aged solar reflectance index (SRI) of 64.  SRI is a calculated value based on reflectivity and emittance.  It’s important to understand why a cool roof is desired and to make appropriate design decisions.

To locate metal roof products that meet the IECC requirements, go to http://coolroofs.org/products/results and use the search function to narrow your results or view our finishes’ SRI ratings on our Cool Metal Roofing page.

Reroofing and the Building Code

Reroofing is and always will be the predominant project type in the roofing industry.  Roughly 70-90% of all roofing projects (depending on the year) are performed on existing buildings.  Understanding the reroofing requirements in the building code is critical to proper design and construction.  And fortunately, the reroofing requirements are not all that complicated.International Building Code

The 2015 International Building Code, Section 1511, Reroofing provides the building code requirements when reroofing.  Reroofing projects are divided into two types: recovering and replacement (which includes full removal of the existing roof).

Metal panel reroofing projects must meet the same fire, wind, and impact requirements for roof systems for new construction; however, they do not need to meet the minimum slope requirements (¼:12 for standing seam; ½:12 for lapped, nonsoldered and sealed seams; 3:12 for lapped, nonsoldered, non-sealed seams) if there is positive drainage.  Also, reroofing projects do not need to meet the secondary drainage requirements (i.e., installation of emergency overflow systems is not required).

The requirements for metal panel and metal shingle roof coverings are in Section 1507.4, Metal roof panels and Section 1507.5, Metal roof shingles of the 2015 IBC.  These apply for new construction and reroofing, and include information about decks, deck slope, materials, attachment, underlayment and high wind, ice barriers, and flashing.  The 2012 IBC has the same requirements; the 2015 IBC added new language about deck slope and attachment requirements for metal roof panels.  Nothing was changed for metal roof shingles.

In general, recovering is only allowed if there is one existing roof in place, except if a recover metal panel roof system transmits loads directly to the structural system (bypassing the existing roof system).  This provides a great advantage for metal panel roofs!  The existing roofs do not need to be removed, but new supports need to be attached through the existing roof (typically a metal panel roof) directly into existing purlins.

If metal panels or metal shingles are installed over a wood shake roof, creating a combustible concealed space, a layer of gypsum, mineral fiber, glass fiber, or other approved material is required to be installed between the wood roof and the recover metal roof system.

Good roofing practice is codified in the reroofing section of the IBC; contractors who design and install a recover or replacement metal roof are legally required to follow locally adopted code requirements.  And, of course, all metal roofs must be installed according to the manufacturer’s approved instructions.

Air Barriers and Vapor Retarders

Air Barrier Vapor Retarders

Building design and code requirements are readily becoming rooted in building science, which is the study of heat, air, and moisture movement across the building envelope.

Reducing the heat energy transfer (which is bi-directional based on geography and climate) is why insulation is used.  And arguably more important is the need to reduce airflow (aka, air leakage) across and through building envelopes.  This airflow often includes a lot of heat and moisture; therefore, buildings’ HVAC systems work hard (and use energy…and cost money) to make up for the heat and moisture gains and losses in order to maintain proper interior temperature and humidity levels.  Environmental Building News, in an article titled The Hidden Science of High-Performance Building Assemblies (Nov. 2012) , stated “Air infiltration and exfiltration make up 25%-40% of total heat loss in a building in a cold climate and 10%-15% of total heat gain in a hot climate.”  This is why the model codes are now mandating air barriers.

The 2012 International Energy Conservation Code (IECC), Section C402.4, Air leakage (Mandatory) provides the requirements for air barriers in new construction.  Prior to 2012, building codes did not include air barrier requirements.  The first step taken in the IECC was to mandate air barriers in Climate zones 4, 5, 6, 7, and 8 (locations north of the Mason-Dixon Line, in a broad sense).  Climate zones 4 through 8 are heating climates, where the largest potential for heat loss occurs.   The IECC provides three ways to comply; air barriers requirements can be met through material, assembly, or whole building testing.  A blower door test, used to test a whole building, seems to be the most common way used to show code compliance currently.  The IECC included a list of materials that prescriptively meet the code requirements for air barrier materials; sheet steel and aluminum are on that list.

Three years later the 2015 IECC went a step further.  Section C402.5, Air leakage—thermal envelope (Mandatory) extended the requirement for air barriers by mandating their use in all climate zones in the United States except zone 2B, which is a hot/dry zone.  Climate zone 2-dry includes only southwest Arizona, southwest Texas, and a small part of Southern California.  Essentially all new buildings in the United States are required to have air barriers, and sheet steel and aluminum remain prescriptive air barriers.  It’s important to know that when reroofing, the air barrier requirements do not apply.

The IECC is available for purchase on ICC’s website:  www.iccsafe.org.

MBCI Welcomes Insurance Institute of Building & Home Safety to Witness In-House Testing

To ensure our products perform as expected, MBCI conducts a variety of tests at our onsite laboratory in Houston, Texas. On April 16, MBCI and our parent company, NCI Building Systems, welcomed several researchers from the Insurance Institute of Building and Home Safety (IBHS) to our Houston headquarters to witness ASTM E1592 testing on MBCI’s standing seam roof panel Double-Lok. This test is designed to evaluate the structural performance of a standing seam roof system under uplift loading experienced by roofs during wind events.IBHS, NCI and MBCI at MBCI Testing Facility

IBHS conducts research to improve loss prevention-related design practices and better understand the risks of insuring buildings and homes.  IBHS’s facilities include a full-scale wind tunnel in South Carolina which recently tested a 30’ wide, 50’ long building by our sister company, Ceco Building Systems, using the same standing seam roof system used in the E 1592 test.  IBHS’s researchers joined our testing to observe how manufacturers test their own products so they may develop design-related loss prevention strategies which can help reduce insurance costs for consumers of metal roofing.

NCI’s Senior Research and Development Engineer Mark Detwiler, who was present at the testing, said “[IBHS] indicated that the test they witnessed reinforced that the industry rigorously tests their roof systems. They also noted that the failure mode they witnessed was consistent with what they have seen in their loss investigations, meaning that the test yields realistic, predictable results.”

Learn more about Double-Lok, ASTM E1592 testing and IBHS and their research efforts.

Part II – Transparency in Building Products

Transparency in Building Products

A huge buzzword in the building products industry these days is transparency.  The green building movement, which has previously focused on high-performing buildings with a strong emphasis on energy efficiency and fossil fuel use reduction, has increasingly put its cross hairs on occupant exposure risk in the last few years.  Although that change alone is probably enough to start some controversy, how this new emphasis is being implemented is really fueling the fire for new arguments.  If you read our last blog, Part I – The importance of consensus in building standards,  then you should be familiar with how building codes are developed in a consensus-based forum in which all affected parties have some say.  However, many of the movers and shakers of the green building movement have bypassed that forum by folding the requirements they want to emphasize into voluntary programs of their own creation.  At the same time, they lobby owners and building officials to carry some level of compliance to these programs, offering a benefit of being able to say their buildings or communities are “green” by displaying plaques on the façade or being listed on a website.

Although that tact seems fair on the surface, it really puts a lot of power into the hands of self-proclaimed experts to decide on the definition of “green” they want to use for their program. As we discussed in Part I, the ANSI consensus process requires policy-making organizations to transparently prove their competence in subjects they affect with their policy.  Furthermore, they also have to publicly announce the formation of a committee (called a “Call for Committee”) they designate to create and maintain this policy.  They must also allow members of the public to submit curricula vitae for consideration to join the committee without necessarily being a member of the organization.  This introduces a mechanism to balance the power the committee is usurping by having control of the policy going forward.  Unfortunately, no such mechanism exists for many of the authors of voluntary green building programs and the negative aspects of this are particularly pronounced in the area of building product transparency.

One of the most common ways green building programs administer transparency is through the use of a “red list,” which is essentially a list of banned substances.  Using California Proposition 65 or Europe’s RoHS as a model, many of the NGO-based programs related to buildings have some type of requirement that aims to reduce or eliminate the use of ingredients that could possibly be harmful to building occupants.  In many instances, these same NGOs offer third-party listing programs that a building manufacturer can join and have their products declared as meeting the requirements.  Many people see this as a conflict of interest since an NGO, typically funded through donations, is in a position to act as a gatekeeper, allowing in only those companies or industries that support the NGO financially or align themselves with the NGO’s agenda.

But there is a deeper, more disturbing aspect:  Although the list itself may start out as a publicly accepted and scientifically based enumeration of toxic ingredients, NGOs often add other substances that are not known, or in some cases, even suspected, to be toxic in order to dissuade architects from specifying certain products or deploying certain construction methods.  Quite often, the NGO will develop the red list in closed discussion forums where manufacturers have no ability to provide evidence to substantiate that their products are indeed safe.  At best, a manufacturer can ask the NGO to consider exceptions or modifications.  But ultimately, a manufacturer has no assurance that their case has been adequately considered because they are not allowed to attend the forum.  Sadly, this is what passes for transparency in green construction more often than not lately.

This lack of due process came to a head in 2013, when members of congress began to express concern that LEED, the green building program used by the military and the General Services Administration, was not an ANSI-based standard.  In response, the GSA formally announced that they would take public comment on the subject and decided nine months later that they would continue to specify LEED but other ANSI-based programs would be considered going forward as well.  Meanwhile, the military announced that they were developing their own standard, distancing themselves from LEED.  This quelled the discussion for a while and allowed other, even hotter subjects like healthcare to take the spotlight.  But concern lives on that the lack of transparency in the development of LEED and similar programs is leading the public down a dangerous, politics-as-usual road.

However, the news is not all bad.  There are several organizations that use an ANSI-based process to develop and maintain their programs so that the requirements can readily be incorporated into public policy.  ASHRAE, ICC, and a newcomer in the U.S., The Green Building Initiative, have all invested the tremendous amount of time and effort it takes to develop their standards in an ANSI-based public forum, and their respective programs offer a building owner or code official a great alternative to vague voluntary programs subject to interpretation by self-proclaimed experts.  We will explore several of those options in our next blog.

Standing the Test of Time: New Study Reveals 55% Al-Zn Alloy Coated Standing Seam Roofs Last 60 Years

The majority knows that metal roofs are durable, but it wasn’t until recently that a study showed the longevity of low-slope unpainted 55% Al-Zn alloy coated steel standing seam roofing (SSR) systems- 60 years. With the service life of a commercial building being 60 years, according to LEED version 4, this means that essentially the metal roof system described above, and commonly referred to as Galvalume® metal roofs, does not require replacement. To put this into context, by comparison most non-metal roofs require at least one replacement during the same period. This study also reveals that the longevity of a 55% Al-Zn alloy coated standing seam roofing system far surpasses the typical warranty period granted, which is 25 years. Basically, this is a game changer and we, manufacturers, are thrilled!

Technical Director of MCA Scott Kriner said, “This study is a breakthrough for the metal construction industry because it finally provides third-party, scientific data that backs up the long held stance that 55% Al-Zn coated steel standing seam roofing systems are very durable, economic and can be better for the environment.”

Let’s take a closer look at the study. The Metal Construction Association (MCA) and Zinc Aluminum Coaters (ZAC) Association sponsored it. The study involved three independent consulting firms testing 14 buildings in five climate zones. The variety of structures and climates allowed them to analyze how Galvalume metal roofs perform in a range of temperatures, humidity and precipitation pH, or acidity, levels. All of these can affect the metallic corrosion rate of roof panels, their sealants and components, and that’s what the consulting firms analyzed.

Here were some of their findings:

  • First, the sealant life is the primary deciding factor in establishing end-of-life for Galvalume metal roof systems. In certain structures analyzed that were 35 years old, the sealant was considered “entirely adequate and without issue.” Based on the sealant performance, the study conservatively projected the lifespan of such roof systems to be 60 years.
  • Secondly, although a Galvalume metal roof is moderately maintenance-free, all roof systems require a periodic inspections and maintenance in order to achieve such long lifespans.
  • Thirdly, while the roof system as a whole was projected to last up to 60 years, components may need to be replaced during this period. The cost of replacing components, however, is considerably less than 20% of replacing an entire roofing system, which is the value deemed by this study as excessive to the point of constituting the end of service life for a roof system.
  • Lastly, the study unveiled that even on areas typically most susceptible to corrosion, such as panel profile bends, there was an absence of significant rust after 35 years; even at its most vulnerable areas, a Galvalume metal roof system performs well.

So what does it mean for architects and building owners? Speaking from a purely biased manufacturer’s prospective, specify and purchase more metal roofs! All jokes aside, this study displays the appeal in selecting a metal roof because it reduces the maintenance costs of the building. It also changes and increases the accuracy of Life Cycle Cost (LCC) or whole building Life Cycle Assessment (LCA) associated with Galvalume metal roof systems by providing tangible research as opposed to previous calculations based on roofing professionals’ opinions. To find out more information or to download the full report, visit http://www.metalconstruction.org/index.php/education/technical-resources.

Separating Fact from Fiction: Let Your Meter be Your Guide

Being a building scientist is kind of like being a librarian. You have to separate fact from fiction. Case in point: The Green Building Movement. I’ve been a building designer for 20 years and I have never seen the kind of change and repositioning of building science in the time that I’ve seen in just the last five years. And of course, with that come agendas, minutia, politics and confusion. It’s unavoidable. So, when people ask me about green building, I feel the duty to encourage them to stick to what is tangible and measurable and try to stay out of speculation. Yeah, ok, that’s pretty obvious advice. But it cuts deeper than that because you actually have to track meaningful, FACT-BASED metrics.

Consider the regional material credit in LEED. The purpose of that credit is to avoid burning fuel to transport raw materials to the project site. So, if the final manufacturing location of a product is within a 500 mile radius of the project and you can prove that the material used in the product was extracted and/or harvested from the earth within that circle as well, you get credit for using it.  But does that truly guarantee the minimum carbon footprint? Most products used in buildings have been through a long and complex supply chain of co-mingling and transportation between intermediate points and the simplistic criterion of only considering the end points of that chain isn’t going to guarantee any level of performance, so why track the metric?

At the other end of that spectrum is energy use. This is NOT the same as energy efficiency, mind you. The definition of efficiency is the amount of work done divided by the amount of resources consumed to achieve that work. If my efficiency is 1, then I’ve wasted nothing. If it’s zero, I’ve wasted everything. It seems like a good metric to use, but it isn’t always obvious what number to use in the numerator (that’s the top number in a fraction, by the way) which makes efficiency somewhat subjective as a metric.

Electricity use on the other hand, is an absolute metric. You use electricity and have to pay for it. You have a meter to tell you how much you’ve bought. That’s a pretty convenient thing because you don’t need a fancy computer with wireless controls and bells and whistles (which use electricity, by the way) to print a graph of your electricity usage. All you have to do is get up off your derriere and look at it.  (Yes, it is unfortunate that meters are outside but you need the sun exposure to produce Vitamin D anyway.)

So when it comes to things like roof top solar, the subject of my last blog, the energy you make directly offsets the energy you use. The meter “spins” slower or even backwards (net-metered solar installations use digital meters, but whatever) and at the end of the month, less electricity is used.  Simple, predictable and efficient; there is no question what your impact is.

Now when it comes to energy used for climate control, you are in a quandary.  The energy you use is going to be highly dependent on the outside conditions, so how do you account for that? Well, the fact of the matter is that weather, although it varies quite a bit from day to day and year to year, follows a very consistent pattern over time and some things you can do will always make a difference.

Most commercial buildings are under insulated. We know that from studies conducted over many years by the government. The reason is simple: Commercial buildings are not usually built by the electricity bill payer, so the motivation to invest in things like extra insulation and insulated windows is not there. Therefore, if you should inherit a commercial building for your business, before you move in, you should probably peel back those ceiling tiles and tap on that glass to see what is between you and the outside world.

Should you discover that you need a little extra help, there are some great products on the market these days and one of them is spray-foam insulation. However, if the building is old enough and needs a new exterior finish on the roof or wall anyway, consider an all-in-one solution like an insulated metal panel. This product combines one of the most durable exterior materials around – coated steel – and the same great insulation performance as the spray-on foams without the special equipment. Plus, the excellent air barrier performance minimizes air infiltration. And here is a tip: Roof or wall, choose an exterior color that fits your climate. Consider using lighter colors in the south and darker colors in the north.  That can make a substantial difference if the building is under insulated. The poor meter won’t even know what hit it.

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