Sloped, standing seam, metal roofing provides a continuous surface that is designed to shed water efficiently while providing a long-lasting and great looking roofing solution. When the roof design and shape is simple, (i.e. continuously extending from ridge to eaves with no changes or interruptions) then all of the attributes of the metal roofing can be assured by using some very conventional and well-known details for design and construction. But in the real world, there are lots of conditions that require more specialized attention to detail. For our purposes here, we will simply refer to those as “specialty roof conditions.”
What types of roofing conditions warrant the special attention? Most are associated with changes in the shape or surface of the roof, say where the ridge line is interrupted or offset. Others could be a means to accommodate a roof feature such as a dormer, a dutch hip type of roof, or the intersection between a ridge and a parapet wall. Some might be related to the design of a valley, particular if it is a “dead valley” that doesn’t drain directly to the gutter but stops short, as around a dormer or elsewhere. Or some could be the result of some special conditions created by the roof design such as cascading water over an edge or heavy snow accumulation conditions. There are certainly many others too, but the point is that any of them are a potential source of water leakage and building damage if they are not properly addressed.
Above is an example of a special roof transition created by MBCI.
Most metal building manufacturers not only recognize the importance of such specialty roof conditions, but they also have lots of experience in developing very workable solutions for them. The key for success is found in the fundamental principles of properly overlapping (i.e. “shingling”) all materials to allow water to drain smoothly away where it is intended without getting diverted to places where it shouldn’t go. That means the metal roofing panels need to be cut, fit, and installed properly, but it also means that flashing, sealants, and fasteners need to be installed correctly too, all regardless of the slope of the roof. To communicate ways to achieve better results in the field for specialty roof conditions, manufacturers like MBCI make step-by-step details available for installers. The significance of using and following these details can not be overstated since they are a key component in getting a weathertightness warranty from the manufacturer.
As an example of how this might play out on a specific building, let’s look at a dead valley that occurs because a gable roofed dormer is installed in the main area of a roof. The first thing to recognize is that multiple layers of materials are involved in the transition around the dormer, all of which need to be installed in the proper location, following the proper sequence, and with the proper connections. A step-by-step process as detailed by the manufacturer might look like this:
Step 1:
With the substrate in place (rigid insulation over a metal deck), a special width panel will likely need to be installed and serve as the collection area for the dead valley to drain into. Then, plywood spacers and nailers are installed, and the main lower valley area is covered with “rubber” (EPDM) flashing.
Step 2:
Secure continuous eave trim over the plywood nailers and add and offset cleat on top to receive roof panels, all secured with tri-bead tape sealer and fasteners as shown.
Step 3:
Install extended valley trim across the valley with an offset cleat on either side secured as shown.
Step 4:
With all of the prior steps in place, then the installation of upper panels can begin to interface with the edge of the dead valley.
Step 5:
Continue cutting and installing panels to fit over and drain into the dead valley, which then drains without interruption onto the special width panel and the roof.
By following step by step details from the manufacturer for this or other specialty roof conditions, then the likelihood increases that everyone involved in the project is both proud and satisfied with the end results. The key is to start at the beginning with the proper planning and preparation by communicating with the manufacturer about all roof conditions that require special attention like this example.
Energy codes and increasing energy costs have prompted the installation of more roof insulation into metal buildings in recent years to make them more energy efficient. That is fundamentally a good thing and metal building manufacturers have developed ways to accommodate a variety of building enclosure packages that increase energy performance while still being engineered to meet the structural requirements of the building. This allows the whole building envelope to be designed and fabricated so it works as a complete, coordinated system.
Insulation helps maintain a comfortable interior temperature in your metal building during the winter and summer months.
The metal roofing or metal building suppliers typically don’t design the insulation systems. However, it is important to include them in the discussions or make them aware of what type of system is to be installed. It is not uncommon for a metal building to be ordered with the design stipulation of “insulation by others.” In that case, coordination is needed between the person ordering/designing the insulation system and the metal building manufacturer or roofing supplier. Since there are a great many variables in the way that insulation can be provided, it is not appropriate to think that the design of structural systems (purlins and roof bracing) and cladding systems (clips, fasteners, and metal roofing profiles) will necessarily accommodate all the same insulation in all conditions. Rather, unless the specific details of the insulation system being used in the building are communicated effectively at the time of the order, the manufacturer can not assure compatibility of the systems used with the insulation system that is to be installed.
In order to understand some of the variability in the options, let’s look at some of the common ways that metal buildings are or are not insulated.
Uninsulated Roofs:
Buildings that do not have any heat or air conditioning in them may not need for an insulated roof. This could be true for outdoor shelters, some agricultural buildings, or vehicle storage buildings. However, uninsulated metal roofs have the potential for “roof rumble” as they move due to thermal expansion and contraction, wind, or weather as there is no insulation to mask or deaden this noise. Absence of insulation can also lead to condensation during certain times of the year if temporary heat is added to the building. This condensation builds up and can drop or fall onto whatever is below. Many times condensation issues are mistaken for roof leaks when in fact it’s a mechanical design issue of the building envelope that’s not been properly addressed. If neither sound nor potential condensation are a concern, then there’s no problem. But if either or both need to be avoided, then some basic level of insulation may be prudent.
Over the Purlin Systems:
One of the most common insulation systems for metal buildings and/or open framing systems is to simply install rolls of blanket insulation. In this case, fiberglass insulation with a reinforced liner is draped over structural beams and purlins. The rolls are supplied to length by the insulation supplier based upon the roof structural layout and the required “R” value necessary for the building envelope in thicknesses that can vary from 3″ to 12″. Is is this thickness to be installed over open framing that the metal building/roofing supplier must be made aware of. Based on this thickness, the panel profile can be verified to determine if it can be used as well as confirmation of the correct clip heights and screw lengths for installation. Keep in mind that the supplier will offer a guide to the installer based upon insulation thickness. As insulation can vary by manufacturer, it will be up to the installer to make adjustments as needed in the field to ensure proper placement and hold modularity of the steel system. (See Respect the Module: Metal Roofing Panels are Modular for Good Reason)
Cavity Fill Insulation Systems:
When higher “R” values are required for roof insulation, a single layer over the open framing system may not be sufficient. When that occurs, the designers of the building envelope may need to employ the framing cavity to add more insulation. There are also variation on the cavity fill approach.
One means is to simply introduce a second layer of unfaced blanket on top of the faced insulation. Sometimes referred to as a “sag and bag” approach, here the first layer of insulation over the purlins is ordered to accommodate larger amounts of drape between the roof structure to permit another layer of unfaced insulation to be added on top. This increases the insulation thickness between the purlins but keeps it thin enough to be compressed to accommodate the roof panel installation. For coordination purposes, the thickness of this upper insulation over the purlins needs to be known by the building manufacturer so the clips and fasteners can be properly sized. Likewise, the amount of insulation draping between the purlins needs to be known to determine if purling bracing or other accessories may potentially interfere with the insulation installation.
Other types of cavity fill system may include a faced batt or face roll insulation with long tabs, which are secured to the tops of roof purlins and nest fully into the purlin cavity to fill the space more effectively. This helps in eliminating greater compression of multiple layers of insulation on top of the purlins and permits an additional layer of unfaced insulation on top of the roof structures and/or a thermal spacer block. This system may also require some intermediate banding to support the insulation between the primary supports.
A liner system may be installed that employs a continuous vapor retardent material. This liner is secured to the bottom of the roof structure and additionally supported with metal banding allowing the cavity to then be filled with unfaced insulation between the purlins. More unfaced insulation can also be added on top of the purlins as well. In all of the cases where cavity fill systems are used, it is important to advise the building manufacturer/roof supplier which type is being used to ensure proper panel clip heights and screw lengths. This is important because these systems can and will interfere with the roof structural bracing making them more difficult to install. The metal building supplier may be able to offer bracing alternatives or remedies to eliminate some or all of the bracing that would otherwise be in the way when installing the roof insulation. There may also be suggestions on how to avoid impeding or penetrating the vapor barriers which could lead to condensation issues. Overall, it is best to discuss and coordinate all of these items ahead of time.
Rigid Board/ Composite Systems:
In this insulation approach, rigid foam insulation board is used to achieve the sought after energy performance. Commonly, these use metal deck panels over the roof structure thus supporting the insulation and a vapor retardant material on top of the deck. The insulation and the metal roofing can then be secured to the framing substructure or to the metal deck itself, which means the details of attachment need to be reviewed and engineered to avoid adverse affects on the roofing system.
Minimum decking gauge, clips spacing and clip screw lengths should be considered as well as associated adjustments to labor costs.
Spray-on Insulation:
All of the above systems typically require attention to providing additional air and vapor barriers and proper cutting and fitting during installation so as not to cause unwanted infiltration or to prevent condensation from occurring. For these reasons and more, some people will consider the use of closed cell spray-on foam insulation, which can continuously provide all of these features in one product. It can also be installed after the roof is completed and structure is weathertight.
Any corrosion of the panel due to adhesion of the insulation is not covered by the panel.
In the case of metal buildings, spray-on insulation is typically applied in the field onto the inside face of installed roof panels and sometimes wall panels too. There are, however, a few concerns with this approach in metal buildings. First, if conditions are not right and the panels are not properly prepared, then the spray foam can, in fact, trap moisture between the insulation and the metal components it is sprayed onto. That can lead to corrosion of the metal or deterioration of the insulation. Secondly, not all spray foams on the market are intended for this type of use so they don’t always adhere well to some metal panels, meaning it could become loose and fall away. Finally, continuous spray foam in this application will not always be able to expand and contract at the same rate that metal does. In some cases, that could mean that the foam suffers from differential movement causing it to break or lose adhesion.
For all of these reasons, be certain to research all options before considering or selecting a foam spray-on insulation that will not negatively impact your roof performance. If a foam insulation is preferred, it may be worth considering the use of insulated metal panels (IMPs) that are designed, engineered, and fabricated to be compatible with metal building construction.
Recognizing all of the above variations and options, the key point to remember about insulating metal buildings is the importance of communication between those designing and ordering an insulated metal building and those who are manufacturing and fabricating it. To find out more about the best ways to do that, contact your local MBCI representative.
Many metal roofing installers may think that their years of experience on the job is enough. But even for those who have been putting up metal roofs for a long time, the truth is that if they haven’t put up a particular brand’s roof before, they need to go through that manufacturer’s installer training and get certified. There are several reasons for this.
More and more, architects are starting to specify that an installer must be certified by the manufacturer of the product being installed.
Installers need to know the proper technique and protocols—for a particular manufacturer’s product! After all, you don’t make any money by going back and fixing leaks.
There are many other standing seams that are very similar to those that MBCI sells, and while they may look similar, there will be a number of small differences, such as the way panels are notched or the way sealants are put in. Even the way companies test panels can be different. For instance, if you have a Florida or Dade County approval or an FM approval, that’s all tied into the way the roof system is tested. So, if someone has a project where one of those things is required, it is imperative to make sure the installer is using that brand’s system of doing things, down to every last detail. These are some of the things covered in certification courses.
Certification Courses and Installer Training
At MBCI, we offer a three-day course that covers all of our standing seam panels, and have a separate two-day course for insulated metal panels, which provides advanced installer training in metal roof installation through classroom lecture and hands-on application in a variety of MBCI’s products, assembling roof systems on a mockup to reinforce what was learned from the presentations. Courses take place once a quarter in different locations throughout the United States.
In terms of who should attend certification courses, generally speaking, it’s the person from the company who will be doing the actual work since a certified installer needs to be on the roof any time any work is being done on the roof. He or she is the one we train. And that installer is tied back to the company in order for them to receive certification. That company has to have workman’s comp and general liability insurance. If the certified person leaves the company to go elsewhere, the first company needs to certify someone else.
The Bottom Line of Certification
From a bottom line perspective, it’s important for companies to be proactive in making sure there is always someone on their team who is a certified installer for the products they use—or might use. Not only will they learn tips and tricks for proper installation, but it will also avoid a situation where you have a job, the panels are being delivered the next week and you realize you need someone to be certified. Maybe it’s three weeks until the next certification opportunity. You’ll want to have all that settled before you need it.
Just because you’ve been installing roofing for 30 years, doesn’t mean installer training and certification isn’t necessary. Our best advice is to come to the class and learn all the little idiosyncrasies about whatever manufacturer’s roofing panels you’ll be installing. This is a case where even a little knowledge goes a long way.
One of the most misunderstood aspects of a metal roofing system is the proper use of a vapor barrier. There are many sources of information about this topic – some of which are based on science, some based on anecdotal field experience, and some based on journalism. Here, we will try to break it down to the basic principles that can be used to understand the latest options for a metal building roof system today.
What is Vapor?
The observed science tells us that water can take three forms, depending on temperature and its ability to interact with other things around it. Water can be a liquid that we drink, solid ice that we can skate on, or a gaseous vapor that is part of the makeup of the air we breathe. We can’t see water vapor in the air but we can feel it – we call that humidity. High humidity means a lot of water vapor is in the air, typically coupled with higher air temperature – and both can make us feel uncomfortable and “sticky.” Low humidity means the air is dryer – more typical in lower-temperature air – but this may also be uncomfortable for our breathing, skin dryness, etc.
Why is Vapor a Concern?
As long as the gaseous water vapor stays in the air at a moderate or comfortable level, there is no real concern. However, since water vapor responds quickly to temperature, it can turn back into water as soon as it encounters a surface that is cold enough for it to make the transformation. We know this phenomenon as condensation, and anyone who has seen a cold drink collect water on the outside of a glass on a humid summer’s day has experienced it. It is the same phenomenon that shows up on the surface of windows in a building when there is a big difference between inside and outside temperatures. We know that the amount of water vapor (i.e., humidity) present and the air temperature can both be variable at any given time, but there is always a predictable point at which water vapor will condense and form water drops – this is called the dew point. When vapor in the air encounters a temperature at or below the dew point, condensation occurs.
What Does This Have to do With Metal Roofing?
Metal roofing systems and condensed moisture are not a good combination. If airborne moisture seeps into a metal roof assembly, finds a cool surface, and condenses on any surface there, it likely won’t be visible from inside or outside of the building. That trapped water can then cause rust and corrosion of metal parts, resulting in real damage. It can also collect and saturate building insulation, rendering it ineffective. If enough water condenses, it can cause visible staining or grow mold, causing concerns for people inside the building.
Vapor barriers are used in metal buildings to reduce the rate at which vapor can move through a material.
Do Building Codes Address This?
Absolutely – they require that the building be protected from the possibility of damage caused by water vapor. Since the concern is to restrict the flow of airborne moisture in relatively warm air from reaching a cooler surface to condense on, they call for something to be installed on the “warm” side to prevent that flow. For most buildings across the United States, the warm side is the interior face of the roof and walls. However, if the building is kept cold as in a refrigerated warehouse or storage building, then the warm side is likely on the exterior. The same is true in southern climates where warmer, humid air is the exterior condition and cooler interiors are common.
What is the Best Solution?
Manufacturers of insulating products have been involved in addressing the best ways to provide not only insulation to keep building temperatures warmer, but also vapor barriers to restrict the flow of airborne moisture. After literally decades of trying different types of vinyl and polyethylene facings over fiberglass insulation, most have realized that those membranes simply don’t provide enough protection to be effective. Instead, most are now offering a choice of laminated facings over the insulation that can be installed so they are exposed to the appropriate warm side of the roofing system. These fairly sophisticated laminations include:
Polypropylene-scrim-kraft consisting of layers of white or metalized polypropylene, fiberglass reinforcing, and white kraft paper on the order of 11-30 lb. weight
Polyprolene-scrim-kraft consisting of aluminum foil, fiberglass reinforcing, and 30 lb. kraft paper
Vinyl-reinforced polyester
All of these latest advancements in vapor barriers can provide comparable, high levels of protection, but their selection can depend on a variety of other building factors. Therefore, it is always best to engage an architect or engineer in the design to review the needs of the entire building to select the most appropriate, specific solution for an given project. It will also be important that all seams, connections, and penetrations of the vapor barrier are addressed in the design and construction, which are similarly best addressed by an architect or engineer to assure there are no breaches in the protection provided by the barrier.
The movement of the construction industry to create buildings that are more sustainable throughout their life cycle continues to be a fundamental part of a well-designed and well-constructed building. This comes from the building owners who are expecting it, designers who are more skilled at achieving it, construction companies who have incorporated it into their workflows, and manufacturers who have invested significantly in it. These sustainability efforts include the design, fabrication, and construction of pre-engineered metal buildings across the country.
A number of different certification programs (LEED, Green Globes, The Living Challenge, etc.) promote and can independently certify buildings as meeting different levels of “green” or “sustainable” designs. And the recently released International Green Construction Code has been adopted by a number of localities to codify green design and construction. While the details of these programs vary, they all address some fundamental aspects of buildings, and all apply to metal buildings.
Building Site Impacts:
Shop fabrication of metal buildings means the onsite work can be focused to stay close to the building footprint. Once built, the roofs of metal buildings can further reduce site impacts. For example, metal roofs provide an excellent opportunity to collect rainwater so it can be used for non-potable purposes, such as landscaping or toilet flushing. Further, by specifying metal roofing with a high Solar Reflectance Index (SRI) value, the roofing remains cooler than a dark-colored roof and reduces the so-called “heat island effect” surrounding the building.
Reduces Energy Usage:
Metal buildings can also be designed and constructed to create an energy-efficient building enclosure. The Metal Building Manufacturers Association (MBMA) publishes an Energy Design Guide for Metal Building Systems, available at www.mbmamanual.com, which can help in the process. As MBMA points out, builders can “select the best balance of high-performance roof and wall insulation (including fully insulated metal panels), windows and doors, and foundation insulation that works best and saves the most energy and money when considering all the project requirements.” A metal building with a sloped roof can also be the ideal base to support solar panels that can provide an onsite source of renewable energy for the building to capitalize on.
Responsible Material Usage:
The construction industry has become attuned to looking at the impacts of materials over their full life cycle, and this includes the metal building industry. The MBMA has taken the lead on preparing an industry-wide Life Cycle Assessment (LCA) (http://www.mbma.com/Life_Cycle.asp) that includes primary structural steel frames and secondary structural steel (purlins and girts), along with roof and wall products used in metal buildings. MBMA has also prepared Environmental Product Declarations (EPDs) based on the LCA and industry-wide product category rules. By using this information, designers, building owners, and constructors can determine the environmental impacts of metal buildings from the extraction of raw materials through manufacturing and preparation to ship to the construction site (“cradle to gate”). The fact that steel products of all types contain a significant percentage of recycled material, and can be again recycled at the end of the service life of the building, helps present a more sustainable picture of steel than does some other building products. Further, the shop fabrication of components helps eliminate construction waste on the job site.
At MBCI, we take LEED project documentation seriously and issue only project-specific documentation for USGBC submittals, so please contact your sales representative for LEED documentation on existing contracts.
Indoor Environmental Quality:
The interior spaces of buildings are generally considered sustainable when they protect the health and well-being of the people who use the building. In the regard, metal buildings provide some advantages over others. First, many of the metal building components can be pre-finished before ever arriving at the site. This means that onsite finishing, which can release harmful volatile organic compounds (VOCs) or other substances into the air, are notably reduced or eliminated a the building location. Further, the structural flexibility offered by steel construction means that windows, doors, and skylights can be appropriately spread throughout a building to provide natural daylight and exterior views, which have been shown to have great benefits to the people who work in, visit, or otherwise use the buildings.
Overall, it is the full interaction of all parts of a building, including the owners and users of a facility, that will determine the final sustainability of any building. Nonetheless, it is clear that metal buildings can be a great place to start on the sustainability path. To find out more about metal products and systems that can help your next building be more sustainable, contact your local MBCI representative.
Are you involved with a building project along the Gulf Coast of Texas in which metal roofing or siding is involved? If so, obtaining a building permit may be subject to compliance with the Texas Department of Insurance (TDI) Windstorm Inspection Program. Here is some information that can help.
What is the TDI Windstorm Inspection Program?
In 1987, the Texas Legislature enacted HB 2012 with a requirement to mitigate losses to structures due to hurricanes along the Texas Gulf Coast. On January 1, 1988, the Texas Department of Insurance (TDI) began administrating the Windstorm Inspection Program in support of this legislation. The program is centered in Austin, with four other field offices also located along the Gulf Coast.
Where does the TDI Windstorm Inspection Program apply?
The Windstorm Inspection Program applies to all commercial and residential structures located primarily along the Gulf Coast of Texas. TDI has designated specific areas as catastrophe areas, also known as Texas’ First Tier Countries. The affected countries include Aransas, Brazoria, Calhoun, Cameron, Chambers, Galveston, Jefferson, Kenedy, Kleberg, Matagorda, Nueces, Refugio, San Patricio, Willacy and certain cities east of State Highway 146 in Harris County (La Porte, Morgan’s Point, Pasadena, Seabrook, Shoreacres).
Designated Catastrophe Areas
What is the Texas Windstorm Insurance Association?
The designated catastrophe areas often use Texas Windstorm Insurance Association (TWIA) as the insurer of last resort for the wind and hail portion of their building insurance. To qualify for wind and hail insurance through TWIA, all new structures plus any alterations, additions, or repairs to existing structures (including re-roofs or roof repairs) located in the designated catastrophe areas must be constructed and inspected according to the building specifications adopted by TDI.
How are Building Permits Affected?
All building work needs to meet the requirements of the adopted building codes in Texas (currently the 2006 version of the International Building Code and the International Residential Code). However, in addition to the codes, the TDI requirements must also be complied with in the designated countries. This is similar to other parts of the country that experience severe weather events (e.g., Dade County, Florida) where additional requirements above the code have been instituted for safety reasons. At the time of building permit application, evidence will need to be shown of TDI compliance in design documents; therefore, many times the local TDI office is contracted first and an application is submitted (Form WPI-1). Then, during construction, a TDI certified inspector (usually an engineer) will inspect the work, as will the regular building inspectors. Compliance will need to be shown with the TDI requirements (Form WPI-8) in order to obtain final sign off and a Certificate of Occupancy.
What Building Products are Approved for Use?
In order to be compliant with TDI standards, building products must be independently tested and shown to be able to withstand different levels of severe weather. For products like metal roofing and siding, the testing needs to include the method of attachment and the substrate type (metal, wood, etc.). Product evaluations are available by product type (such as “Exterior Coverings” for metal siding or “Roof Coverings” for metal roofing) and then by manufacturer all by either contacting a local TDI field office or on TDI’s website: www.texas.gov/wind/prod/index
Metal building panels, whether for roofing or walls, are manufactured with a long-lasting and durable finish of different types and in many colors, allowing the panels to hold up and look great for decades. However, once they get to the building they may need to be cut to fit a field condition, or they may need to be cleaned either during or after installation for any number of reasons. Innocently doing either, without understanding that doing it the wrong way could compromise the integrity of the finish, can be disconcerting at best or warranty-buster at worst. Here are a few tips for the proper cutting and cleaning of metal panels.
Cutting Metal Panels:
Field cutting of panels is certainly allowed and acceptable to manufacturers and is common, particularly at framed openings. However, there are two things to pay attention to here:
Cutting Method: If field cutting is required, the panels must be cut with nibblers, snips or shears to prevent edge rusting. Do not cut the metal panels with saws, abrasive blades, grinders or torches. Abrasive saw blades, grinders and torches can leave irregular or rough edges that are no longer coated or finished, thus causing rust and corrosion.
Corrosion on this panel edge is due to an abrasive saw blade cut.
Cutting Location: All cutting of metal will produce fine particles, or swarf, that will fall from the cut. If this swarf falls on the roof, it can cause permanent staining and, if enough of it accumulates in one place, it could rust completely through the metal roof panel. Therefore, never cut metal panels on the roof or over other metal panels. It is best to cut the panel down on the ground where the swarf can be captured and disposed of.
Accumulated swarf from cutting is staining this metal panel.
Cleaning Metal Panels:
Metal panel manufacturers will usually provide information and directions for cleaning. A typical set of cleaning recommendation follows, based on a progression of cleaning levels—start with number 1 and work your way down the list for tougher jobs.
For simple cleaning, water and mild detergent will often be all that is needed. However, bleach should never be used, since it can change the finish color or interact disastrously with certain metals.
For water-soluble dirt or other deposits requiring more complete cleaning, a solution of hot or cold water mixed with detergent is appropriate. In a container of water, use a 5 percent solution of commonly used commercial (non-industrial, non-bleach) mild detergent, so as not to have any deleterious effect on the painted metal surface. Use a cloth or a soft-bristle brush for application of the cleaning solution, followed by an adequate rinse with clean water. Alternatively, pressure-washing with a 40° tip is also an option.
For non-water-soluble deposits such as tar, grease, oil and adhesives, a solvent or alcohol-based cleaner may be required. In this case, since most organic solvents are flammable and/or toxic, they must be handled accordingly. Generally, keep them away from open flames, sparks and electrical motors. Use adequate ventilation, protective clothing and goggles, and read the manufacturer’s Material Safety Data Sheet (MSDS) of any solvent used for any other specific safety details. The following are among the cleaners recognized by manufacturers for this type of non-water-soluble cleaning:
Alcohols
Denatured alcohol (ethanol)
Isopropyl (rubbing alcohol)
Solvents
VM&P naptha
Mineral Spirits
Kerosene
Turpentine (wood or gum spirits)
Regardless of the level of cleaning required, never use wire brushes, abrasives, or similar tools that will abrade the surface coating and leave scratches or other finish damage and lead to corrosion. Further, keep in mind that any misuse or abuse of any of the acceptable cleaning agents will automatically void any manufacturer’s warranty for the affected surfaces.
By using the tips above to properly cut and clean metal panels, installers can avoid the problems of corrosion, staining or other surface damage. Thus, the integrity and beauty of the finish is maintained without any impact on the warranty. To learn more about metal panel finishes, cutting, cleaning and warranties, contact your MBCI representative.
On a very basic level, specifiers can look at a climate zone map and get an idea of the metal roof panel best suited to a specific geographic region. The issue, however, is actually much more complex. One must know that overlooking any detail could result, not only in less-than-ideal performance, but also in costly project fail, often related to the project not meeting required energy codes or other standards. With this in mind, an important initial question to consider is how to select metal roof panels that conform to new and fast-changing energy codes and their designated climate zones.
To begin making wise considerations, the architect must know what codes are in play. For instance, is it IECC or ASHRAE 90.1? Which year of the code/standard? Are there additional local code requirements? Even if a state adopts a particular energy code, it doesn’t necessarily mean that all jurisdictions will adopt the code at the same time. Along with this, some local jurisdictions may have their own or additional requirements. To be successful, it is imperative to know what the regional project goals and requirements are. This will require research prior to specifying the metal roof panel and its assembly.
Using IECC and ASHRAE 90.1 for Energy Code Compliance
Three of the basic metal building roof panel types are single-skin standing seam, screw-down and insulated metal panels (IMPs). When using the tables in IECC and ASHRAE 90.1 for metal building roofs it must be remembered that these tables are based on single-skin standing seam roof panels and purlins that are 5′ on center. The tables provide the required R-values and/or U-factors based on climate zones, along with other assembly requirements noted with each tables. In the Appendix of some versions of ASHRAE 90.1, there are allowances for modified roof assemblies, including screw-down metal roofs.
DOE-Developed Climate Zone Map
Often, in certain climate zones, the required R-values and U-factors may be so stringent that the logical first consideration is to use insulated metal panels. IMPs are a great choice for offering high insulation properties in a top-of-the-line product and the R-values and U-factors are readily available for use in compliance calculations.
Keep in mind when deviating from the prescribed assemblies in IECC and ASHRAE 90.1, calculations will be required to show compliance, along with modeling and/or the use of approved compliance software, such as COMcheck.
Making Informed Decisions
Selecting the right metal roof panel is an important step to achieving energy code compliance. Even though energy codes can be complex and are constantly evolving, by making informed metal roof panel selections you will add to the overall success of your project.
Top Five Tips:
Know your code. Find out what energy code is required for your project.
Know your zone. Requirements vary by climate zone. Identify your project’s climate zone.
Understand your options. Deviating from specified assemblies will require approved proof of compliance.
Choose wisely. Research the properties and assembly requirements of any metal roof panel. Use this information in conjunction with energy code requirements to make wise choices.
Call with questions. Call the manufacturer with questions before you get too far down the road.
Described in their most basic terms, R-value is a measure of heat resistance, while U-factor (also know as U-value) is a measure of heat transfer (heat gain or loss). The lesser known K-factor is simply the reciprocal of the R-value of the insulation divided by the thickness. What they all have in common is a relationship to the effectiveness of insulation material in resisting heat flow through a roof or wall element. There are different ways that this would be spec’d from a manufacturer to an architect or engineer. While the terminology might be familiar, the specifics are not always as clear cut as they seem. Understanding the differences will allow architects to make smart and effective choices to suit a given project’s needs.
Let’s consider some of the variables that might have an impact on what to look for and which metric to spec. As means of illustration, put yourself in the shows of a fiberglass or insulation supplier. You have a product, you know what it’s rated to, you know what the performance capability is, it’s been spec’d out to you—and you submit the bid based on those factors. But at that point you inevitably lose control over how the specs would actually get implemented. For instance, the architect may take that spec and incorporate it into a wall where it’s not used the most efficient way. This may not even be the result of a mistake; it could just be that other project elements have taken over.
Choosing the right insulation for the project can provide the building significant energy savings.
A good example would be stud walls. The fiberglass insulation supplier might indicate a given R-value, such as R-19. This would be the heat resistance value. The architect might spec and submit that bid to supply x number of square feet of that insulation based on that R-value. However, it could be cut or delivered in rolls and designed to fit between the metal studs. Metal studs are much more conductive than insulation and they provide an alternate path for the heat to flow through the assembly, almost irrespective of what the R-value and insulation is. Given these factors, the architect might have to make tradeoffs.
Choosing U-Factor
Because of all the variables encountered with R-value, U-factor is actually more recommended and reliable, and it more appropriately meets code requirements.* The concept of U-factor relates to the heat transfer coefficient but is described in the code as total heat flow per unit area through the assembly inclusive of all the short circuits as it is planned out to be built. So, an architect or engineer would know the stud spacing, the cladding material, the interior finish material and the R-value of the insulation. With that information in hand, one can go to a textbook, ASHRAE 90.1 or the ASHRAE Book of Fundamentals and find the U-factor for the assembly. It is this U-factor that is actually compared against the code requirements. It’s a better way to spec because it already takes into consideration all those things that come into play and encourages the use of suppliers (such as MBCI) that staff people who can help do those calculations or give assistance as opposed to saying, “I need R-19” and then wind up with a building that’s bridged or has more short circuits than anticipated—and having the building not perform as needed. This, in essence, is the key difference between R-value and U-factor.
A Word About K-Factor
As for K-factor, as noted this is the thickness of the insulation divided by the R-value. Its intention is to spec out an insulation when you’re not entirely sure what thickness it will be at the time you spec it out. This is fine for design-build scenarios but not a good practice for a hard bid. Bottom line: U-factor is most often the most reliable choice.
*Note: The code defines U-factor as discussed but underlying heat transfer theory may describe U-factor as 1/R-value. Insualtion suppliers might invert it and make it an R-value (but doesn’t take all the variables into consideration). Therefore, an architect would be advised to specify a “U-factor in compliance with ASHRAE, ” which includes thermal bridges, joints, etc.
Once upon a time, a “standard warranty” was indeed the industry standard for weather tightness warranties in the metal roofing realm. To make a long story short, this meant that manufacturers supplied a “manufacturer’s standard warranty” based on an initial review of the details to ensure that the roof could be properly installed but left it up to others to ensure that the details were followed. If the roof was not properly installed and resulted in a leak then the manufacturer’s warranty did not cover it. At this point, the project had been closed out and the installer was long gone, sometimes even out of business. The owner, architect, general contractor, installer and manufacturer were then at odds with each other leading to dissatisfaction and frustration all around.
Warranty Evolution
In the mid ’90s, the Single Source or Day One warranty was born and quickly caught on throughout the metal roofing industry. Generally, this warranty required that the roofing contractor come to the manufacturer’s training course to be trained in the proper installation of their roof system(s). In addition, the manufacturer typically required inspections at the beginning, middle of the roof installation with a final inspection just before the crew demobilized from the project. Once the warranty was issued, the manufacturer was responsible to the building owner from the date of substantial completion for the weathertightness of the roof. To be sure, there are still terms and conditions to the warranty, just like with any type of product warranty. For instance, the warranties don’t cover leaks caused by natural disasters or damage caused by other trades on the roof. These warranties provide very good coverage and the best part is that the inspections greatly reduce the chance of a leak in the first place, which is what any building owner would want.
Chain of Lakes Elementary School featuring Hunter Green SuperLok® Metal Panels
There is an overwhelming agreement on all sides that the evolution toward the Day One warranty has been a good thing for the industry. It has forced installers to do things right from the outset and has compelled manufacturers to come up with good, clear details for some of the more complex architectural elements that architects want to use such as dormers, hips, etc.
Conclusion
Manufacturers all want their roof installations to go smoothly, to look good, be trouble-free and perform as expected for many years. To that end, they are willing to work with specifiers, roofing contractors and others to provide assistance, training and job specific help as needed. To ensure that the roofs are properly installed, the specifiers and contractors need to work together with the manufacturers to ensure good communication about the requirements for the specific project and what each party needs to make the project successful.
