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Better Barriers: Meeting Thermal Performance and Controlling Air & Moisture

Posted on December 10, 2015 by Robert Baker

Panelized metal exteriors have joints. It’s just a rule of best-practice design. Yet these joints are seen by some as interruptions in the façade or roof, when in fact they are connections — the opposite, one can argue, of the word “interruption” that suggests a discontinuity.

In fact, engineered metal panel systems offer arguably the best possible continuous exterior system. Not only are they properly applied exterior to the building structure—outboard of columns, joists and girts—but they are also designed to ensure an unbroken chain of thermal control and barrier protection. Combined with controlled penetration assemblies as well as windows, doors and skylights that are engineered as part of the façade and roof system, the insulated metal panel (IMP) products provide unequaled performance.

That’s the main reason that specialized facilities designed for maximum environmental barrier control are made of IMPs: refrigerated warehouses, R&D laboratories, air traffic control towers and MRI clinics, to name a few.

But any facility should benefit from the best performance possible with metal roofing and wall panels. Consider insulation shorthand for the code-mandated thermal barrier required for opaque wall areas in ASHRAE 90.1 and the International Energy Conservation Code (IECC). For a given climate zone, says Robert A. Zabcik, P.E., director of R&D with NCI Group, the project team can calculate the functional amount of insulation needed by using either the “Minimum Rated R-values” method or the “Maximum U-factor Assembly” calculation. For IMPs, teams use the Maximum U-factor Assembly, which can be tested using ASTM C1363.

With IMPs, the test shows thermal performance values up to R-8.515 and better per inch of panel thickness, meaning that a 2.5-inch-deep panel would easily meet the IECC and ASHRAE minimums.

With metal roofing panels and wall panels, a building team can achieve needed energy performance levels with this single-source enclosure, providing a continuous blanket of protection.

The same is true for air and moisture control. In a July 2015 paper by Building Science Corp., principal John Straube wrote, “Insulated metal panels can provide an exceptionally rigid, strong and air impermeable component of an air barrier system.” He noted that, “Air leakage condensation cannot occur within the body of the insulated metal panel, even if one of the metal skins is breached, because all materials are completely air impermeable and there are no voids to allow air flow.”

In terms of water control, Straube writes that IMPs have a continuous steel face that is a “high-performance, durable water control layer: water simply will not leak through steel, and cracks and holes will not form over time. The exterior location of the water barrier,” he adds, “offers some real advantages.”

Connecting the panels at transitions, penetrations and panel joints is the key, of course. Straube notes that sealant, sheet metal, and sheet membranes are effective and commonly used to protect joints.

In my experience, these joint details are incredibly effective. They often outlast most other components of the building. Even more important, they help make IMPs better barriers that meet thermal, air and moisture performance needs. They help make metal panels one of the best choices of all.

Part III – Transparency Plus Consensus: A Win-Win for Everyone

Posted on September 30, 2015 by MBCI

It has been a long time since my last blog on this subject. This is not only because I’ve been busy but also because the landscape of green building programs in general has changed significantly since Part II, and I wanted to wait to see how things shook out before I wrote something that might be immediately outdated. If you remember, we left off in Part II talking about how LEED, the most popular green building program in the US, has not been developed through an ANSI accredited consensus process. Furthermore, the resulting lack of transparency was dubiously ironic given that LEED demands a high level of transparency from building product manufacturers min the latest version of their program, LEED v4.

We also discussed the related but more general movement for manufacturers to fully disclose all of the ingredients in their products to a third party who then compares that list to lists of known hazardous substances and disclose any matches on a product label or public disclosure for all to see. This movement has been fueled by several large architecture firms sending letters to building product manufacturers threatening to stop specifying their products unless they participate. Although most manufactures agree that there is merit to disclosure and are anxious to participate in a fair program, they have not been privy to discussions regarding the logistics of such a program nor have they been allowed to participate in any kind of a standard development governing the disclosure process. This makes manufacturers reluctant to participate, given their vulnerability in such a situation. This risk is leveraged by the fact that currently the only standards that dictate the rules of such a program are under the control of consortiums who have little to no scientific expertise and, frankly, have not been friendly to the building products industry in the past.

I also mentioned that there are alternative programs to LEED that have been developed through a valid consensus process. Specifically, the International Green Construction Code (IgCC), ASHRAE 189.1 and Green Building Assessment Protocol for Commercial Buildings (also known as Green Globes) are ANSI standards that outline the relevant requirements for anyone to view. However, the USGBC marketing machine and resulting popularity of LEED prevented wide use of these standards. Thus, they remained largely unutilized. That is until this year, when the USGBC, IgCC and ASHRAE signed a Memorandum of Understanding, promising to work together and create a favorable consensus by eliminating duplication of provisions and assigning an area of responsibility for each group to maintain separately.

Although no documents have yet to be created, it appears that the administration and enforcement provisions of the new standard will come from the IgCC, and the technical content will come from ASHRAE 189.1, both of which are consensus based. Meanwhile, LEED will require compliance with 189.1 as a prerequisite to an upcoming interim version of LEED. This approach allows an Authority Having Jurisdiction (AHJ) to adopt the IgCC as a minimum standard of construction; dropping any reference to LEED they might currently have as minimum project requirements for all buildings. This leaves LEED to evolve as a completely voluntary program going forward and push the envelope of green building, which is their core mission. Meanwhile, Green Globes remains ANSI accredited and still exists as a commercial competitor to LEED. This environment should result in a more user friendly application process, the lack of which been a ubiquitous criticism of LEED for years, because Green Globes is much more user-oriented.

So, it appears that the most popular green building programs are poised to move in the
direction of a true consensus, which is fantastic news for everyone involved. However, the creation and development of disclosure programs, which will not be in the initial technical requirements provided by ASHRAE 189.1, remains largely a one-sided affair with no seat for manufacturers at the table. Besides the contentious nature of the subject in general, there are major philosophical questions that have to be addressed before Health Product Declarations (HPDs), or any type of disclosure in general, can be brought into the main stream. That subject is beyond the scope of this blog, but I encourage you to read a very good article on the trappings of HPDs called “Disclosure: The Newest Dimension of Green Building” by Jim Hoff.

The good news is that there may be a viable alternative to HPDs on the horizon. ASTM has a current open work item to develop a true consensus based standard guiding the issuance of a Product Transparency Declaration (PTD), which has much the same intent as an HPD. As discussed in Part I, the development of ASTM standards is a highly transparent process that allows everyone, including manufacturers, to come to the table. I encourage every designer to join ASTM and get involved in this process, especially those firms who participated in the letter writing campaign, and forgo HPDs until PTDs are available.

Yes, it will take a little longer; the reality that the development of consensus based standards takes time. But just like the development of the laws that govern this country, there is far too much risk involved in getting it wrong. Instead, having these standards developed by a consensus-based process is the only way the finished product will be truly useful and meaningful.

Rooftop Solar Energy

Posted on August 18, 2015 by Brad Johnson

The “Sustainability begets resilience” blog ended with a nod to rooftop energy production. So, how will you respond when, not if, a building owner asks you about rooftop solar energy? An appropriate and accurate answer is, “The combination of a metal roof and solar energy is a recipe for a long-term, high-performance roof system,” or something like that. The fact is a metal panel roof is an ideal substrate for a solar energy system.

Installation Methods

Solar energy is the broad term for two sub-categories: photovoltaic (PV) systems (electricity) and solar thermal (hot water) systems. Besides the obvious differences, the rooftop attachment concepts for both systems are quite similar. PV panels and solar thermal panels are commonly rigid with metal frames. Attachment to metal roofing panels can be direct or include rails. Both methods use a customized clip that attaches to the metal roofing panel seam; then, metal-framed PV panels or rails are attached. The need for rails (think “purlins”) depends on the seam spacing and layout of the roof panels relative to the size and layout of the PV or solar thermal panels. Overall roof slope matters, too. Directly attached solar energy systems match the slope of the roof, which is not necessarily the optimum slope for energy production.

Structural & Performance Requirements

Other considerations include the structural load, fire resistance, wind resistance and the use of code-approved materials and components. A solar energy system adds weight to the roof. Does the structure need updating to carry the gravity load as well as any increased wind uplift loads? Adding panels to the roof will increase the sliding load (i.e., drag load) on the clips holding the roof panels to the substructure. And let’s not forget about the potential for snow retention or increased snowdrifts that will add weight.

Fire and wind resistance should be discussed with the manufacturer or designer of the PV or solar thermal system. Fire and wind design are incredibly important, and there are very specific code requirements to meet.

Layout Considerations

Rooftop layout of solar systems, especially PV, should not block drainage or impede roof maintenance. Also, clearance at roof perimeters and access to critical roof areas (e.g., drains, rooftop units) is necessary. Last but certainly not least, check with the metal panel roof system manufacturer about warranty issues regarding a rooftop solar energy installation.

While there are many things to consider when installing solar energy systems on roofs, the long service life of metal panels and the ease of installation certainly make metal roofs and solar energy a great combination!

Code Requirements for Cool Roofs with Climate Zone Specifics

Posted on June 8, 2015 by Brad Johnson

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?
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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.

Air Barriers and Vapor Retarders

Posted on May 13, 2015 by Brad Johnson

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.

When It Comes to Roofing Expertise, It Doesn’t Hurt to Diversify

Posted on May 5, 2015 by Amy Crenan

As is often the case when it comes to your investments, it’s always a good idea to diversify. This also applies to the investment of your construction expertise as a roofing contractor. Even with the mild uptick in new construction activity of late, contractors are smart to explore the additional revenue stream that can come from roof renovations and retrofits.

Most metal roof retrofit work entails adding slope to an existing flat- or low-sloped roof. According to a 2013 article in Metal Construction News, about 25 percent of U.S. commercial, institutional and public buildings are 55 years old or older and consist of flat-roof stock that has reached the end of its service life. Two years later, that percentage is surely higher.

To transition from a flat roof to a sloped roof is a good move, because it will result in lower energy and maintenance costs for years to come. It is also environmentally smart, because metal is one of the most recycled materials used in construction, and metal roofing is 100 percent recyclable at the end of its service life. A metal roofing system provides for additional insulation, as well as the installation of solar panels that reduce reliance on electricity. And in most circumstances, a new metal roof can be installed without having to remove the existing flat roof. A metal retrofit may carry a higher initial cost, but when total life-cycle cost is considered, a metal retrofit will end up being the lowest cost alternative.

A large number of buildings with flat membrane or built-up roofs require a framing system to produce an adequate slope. But this particular type of retrofit can be challenging. In general, the retrofit market is more specialized and much more technical than what roofing contractors are likely used to in the existing metal building market. At the same time, the retrofit market can be very profitable and is worth getting up to speed on.

Whether you’re doing a small retrofit project or a complete renovation, MBCI can assist you with developing a preliminary budget, estimating, engineering, as well as providing a complete set of shop drawings for your retrofit project.

Stay tuned for future posts where we’ll provide some guidelines on how to successfully navigate the design process of retrofitting a flat or inadequately sloped built-up or membrane roof. Adding this diversity to your portfolio of roofing skills will likely net a high return on investment.

Part II – Transparency in Building Products

Posted on April 28, 2015 by MBCI

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.

Metal Roofs & Walls a Big Plus When It Comes to Net Zero Energy

Posted on April 14, 2015 by Amy Crenan

Kickapoo Tribe Government & Community Building features MBCI’s CF Architectural Insulated Metal Panel

Are you familiar with “Net Zero Energy?” No, it’s not that sense of power you got from using that early dial-up Internet browser of the 1990’s (The company, by the way, is still in existence, and comes up in searches for the term Net Zero. Who knew?). The Net Zero Energy I’m speaking of is the enviable, sustainable state achieved when the creation and use of energy within the same building system are equal.

Though achievable, the cost and capacity for producing energy within a building system is greater than that of creating energy efficiency in one. The good news is that metal roofing and ,a href=”http://www.mbci.com/products/wall-products/”>wall panels are extremely useful on both sides of the equation.

On the energy efficiency side, insulated metal panels (IMPs) provide roof and wall systems with the thermal and radiative performance needed for sustainable design. Insulated wall and roof panels provide continuous insulation and eliminate thermal bridges. As building and energy codes become increasingly more stringent, insulated metal panels are an ideal choice for thermally efficient building envelopes.

Baker Hughes features MBCI’s CF Mesa Insulated Metal Panels

On the other side of the equation, a common method of generating energy is through the use of photovoltaics (PVs), and metal roofs provide the best possible surface to host a photovoltaic (PV) array. Solar photovoltaic systems and solar water heating systems can be installed on a metal roof, penetration-free, resulting in high performance with minimal risk. Both the use of IMPs and the installation of PVs on metal roofs can be used with proper designs to maximize building energy efficiency.

Of course, metal roofing, known to last 40 years or longer, is the only type of roof that can be expected to outlive the PV system mounted on it, which results in virtually zero maintenance and a very low in-place cost for the roof and PV system together. A sustainability win, a durability win, and, of course, an aesthetic win. The result is anything but a zero sum game.

Find out more about MBCI’s Insulated Metal Panels

Part 1 – The Importance of Consensus in Building Standards

Posted on March 3, 2015 by MBCI

Most people understand the purpose of a building code: To ensure the safety of the occupants and to establish the minimum accepted performance level of the building and its systems. Fewer people understand that because building codes are adopted into law by a governing body, technically referred to as an Authority Having Jurisdiction or AHJ, they are an in fact an extension of the law or ordinance that brings them into effect. Knowing that, you should not be surprised to learn that like laws, building codes in America can’t just be arbitrarily made up by somebody having the authority and know-how to do so. Instead, they must have gone through some type of consensus process in which all affected entities or their representatives have the opportunity to participate. This concept, called Due Process of Law, is central to many governmental charters such as the Magna Carta and The Constitution of the United States of America and is designed to ensure that a person’s individual rights are not unfairly taken away.

Under the US Constitution, laws are written by Congress and interpreted by judges. Members of Congress are elected by their constituents and judges are either appointed by elected officials or elected themselves. Similarly, building codes are written by consensus bodies, like the International Code Council or ICC, and interpreted by Building Officials, who are generally appointed by elected officials. The code development process used by ICC is one where any interested member of the public can participate and is guaranteed a forum to propose changes and comment on the proposed changes submitted by others using a system governed by Roberts Rules of Order. After discussion and debate, the code committee votes on the individual proposals and those that pass are incorporated into the code, guaranteeing due process. (Actually, it’s quite a bit more complicated than this but for purposes of this blog, let’s just leave it at that.)

However, building codes commonly do not actually spell out all of the requirements for buildings and building systems. More and more, the code will delegate low-level detailed requirements to a different type of document called a standard, and then brings the requirements contained within by referencing the standard in the code by name. Likewise, these standards then must also be developed through a consensus process administered by an adequate standard development body. But because all standard development bodies are structured a little differently, it is not realistic to mandate that consensus process directly. Instead, another independent body called The American National Standards Institute or ANSI, certifies standard development bodies as having a sufficient consensus processes to be deemed as meeting the incorporating code requirements for due process. Examples of these bodies are the American Society of Civil Engineers (ASCE) who develop ASCE 7, the document that determines the minimum load requirements for buildings; the American Society of Testing and Materials (ASTM) a group widely known for developing material and testing specifications for general use; and the American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE), who develops ASHRAE 90.1, the document that spells out the minimum building energy efficiency requirements. If you are an architect or engineer, all of these acronyms should sound very familiar to you.

Another acronym that you are probably familiar with is LEED, which stands for Leadership in Energy and Environmental Design. It is developed and maintained by the US Green Building Council (USGBC) and is the premier green building program in the world. Interestingly though, the development landscape changes drastically when it comes to green construction programs like LEED. You see, the USGBC is not an ANSI accredited standard developer and thus LEED is not an actual official standard, hence the use of the word “program”. How then is it possible that USGBC can have so much say in how buildings, particularly publicly owned buildings, get built? The answer is that they get around this limitation by structuring LEED as a voluntary program and then lobbying the potential owners of buildings, like the US and state governments, into using their program by executive order rather than legislating the requirement directly. If you’ve watched TV at all in the last year, particularly with respect to immigration reform, you know how controversial this approach can be. Nevertheless, it is perfectly legal in this context.

This really has not been a significant issue to date because LEED does have a consensus process (albeit not an ANSI accredited one) and LEED credit requirements have been fairly uncontroversial in past versions. However, LEED v4, the latest generation of the wildly popular green building program, changed all of that by adding credits that are less about design and functionality of the building and more about transparency with respect to building product ingredients to ensure occupant health and comfort. Let’s be clear: Most reasonable people, including building product manufacturers, don’t have a problem with increased transparency and want more occupant comfort and health. But it is how LEED defines “transparency” in version 4 has many people up in arms and they point to the hypocrisy of developing a definition to the word “transparency” during a closed-door meeting with no manufacturers at the table as what is wrong with green building as it exists today. My next blog will explore that concept further.