Design Wind Speed and Warranty Wind Speed
July 10, 2019
We’ve already discussed wind uplift design in a previous SpecTopics post (FM 1-90 vs. ASCE 7); this post will help you understand how those wind speed numbers relate to wind speed warranties. 

To calculate wind uplift for a roofing project, you’ll need to determine the building type and local wind speed. In gathering this information, some designers look at the American Society of Civil Engineers’ ASCE 7 Wind Maps for their area, see a number like 90- or 120-mph, and think that is the wind speed their building will encounter. Therefore, they specify the same speed for their warranty (i.e. 120 mph local speed means I need a 120-mph wind speed warranty). Rest assured, this is not the case.

ASCE 7 maps have contours with the local speeds in 10 mph increments. ASCE 7-2005 and ASCE 7-2010 were relatively straightforward; most of the U.S. was in a 90-mph zone. However, in 2016 ASCE deemed it necessary to have separate maps for each building risk category (Category I, II, III, and IV).

This increased the wind speeds for most of the country, especially for projects with increased risk categories.
Naturally, designers saw this increase and thought that since the local wind speed was increasing, they needed to ask for increased wind speed warranties. (i.e. 130 mph or more). Again, this is not the case.

It’s true that warranted wind speed is the limit of 3-second peak gust recorded at the weather station nearest your building project, measured at 10 meters above the ground, during a weather event that affects your building project. But to achieve wind speeds over 90 mph, a cyclonic windstorm (tornado, hurricane, etc.) is generally necessary.
  
If your building experiences a cyclonic windstorm, there will be flying debris, broken glazing, and other envelope breaches that could cause roof failure (over-pressurizing the building, detachment of decking from structural components, etc.). This would not be covered under a roofing warranty, regardless of the wind speed coverage.

Keep in mind that a roofing warranty assumes that the building remains intact, the decking remains solid, the inside pressure of the building is generally equalized, and foot traffic is limited to maintenance and inspection of rooftop equipment. It is not building insurance. Like fires and vandalism, critical weather events such as tornadoes and hurricanes are covered by the building owner’s insurance carrier.

Choose a warranted wind speed that makes sense for you and your client, but you don’t need to match that with your local wind speed. You’ll just be paying more for something you don’t need.

Always verify your need for increased warranty wind speed before inquiring about matching your local wind speed with the warranty.

Contact Craig Tyler at [email protected] with questions.
January 8, 2020
Air and Vapor Barriers for Roofs

In 2012, the International Energy Conservation Code (IECC) introduced the continuous air barrier requirement for new commercial construction. This meant that air and vapor barriers were now required for walls, and they must be tied to both the roofing assembly and the foundation. For years, many architects and designers only utilized an air and vapor barrier on the roof deck for high-humidity occupancies, such as swimming pools or food processing facilities. But the new requirement meant taking a hard look at the needs of all buildings and what a roof assembly could do for the building envelope. A single-ply membrane, as stated in the IECC and as tested utilizing the ASTM E2178 standard, qualifies as an air barrier and can satisfy the requirement for an air barrier on any given project. So why would you consider adding an additional air and vapor barrier to the roofing assembly? There are a couple of very simple reasons: Reason 1: Air Intrusion. While a properly installed roofing system will not allow air leakage (e.g., conditioned indoor air from exiting the building thermal envelope), it does allow air movement within the roof assembly. As the single-ply roof membrane is on the top of the assembly, indoor conditioned air can infiltrate into the roofing system and travel into the layers of insulation or cover boards. Why is this an issue? See Reason 2… Reason 2: Moisture Migration. Adding a deck-level air and vapor barrier is a great solution to prevent air intrusion and moisture migration. This also allows the wall air and vapor barrier to be tied together at the deck level, which allows the roof to be replaced more easily in the future. The contractor will not be modifying the continuous air barrier when re-roofing, as the roof is no longer that barrier. Carlisle SynTec provides many options for deck level air and vapor barriers: VapAir Seal MD for steel deck construction, direct to deck; VapAir Seal 725TR for Concrete Decks; VapAir Seal Flashing Foam for sealing around penetrations such as pipes; Go to the Air and Vapor Barriers Product Page on the Carlisle SynTec website for more information, specifications, and details. Contact Craig Tyler at [email protected] with further questions.

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December 18, 2019
Cold Weather Installation Tips Part 2 - Membranes and Insulation

As discussed in the previous SpecTopic, "Cold Weather Installation Tips Part 1 - Low-VOC Bonding Adhesives and Primers", specifying and handling of building envelope products is challenging during the colder winter months. Single-ply membranes and rigid insulation boards need some extra consideration, as they can be adversely affected by outside temperatures. For starters, all membranes will need time to "relax" after being unrolled from the original packaging; this applies to EPDM, TPO, PVC and KEE HP. It is also suggested that membrane widths be limited to a maximum of 10 feet for adhered roofing systems. Treat flashing products and accessories as you would adhesives and primers, by utilizing heated storage enclosures or "hot boxes". This practice is strongly recommended when ambient temperatures are expected to fall below 40°F for an extended period of time. In all applications, but especially in cold conditions, insulation and underlayments must be stored so that they are kept dry and protected from the elements. Insulations should be stored on a skid, covered with a breathable tarp, and weighted to prevent wind damage. In winter months, ice and frost can form on the membrane. This can be difficult to see and can remain on the roof well into the day, especially on white membranes. This can be especially hazardous when working near the edge of the roof. Additionally, frost on metal edges and copings can create a very slick surface and cause ladders to slide and shift. Never step onto a metal coping when it is frost- or snow-covered. So for your next cold weather specification for single-ply membranes and rigid board insulation, include some installation precautions as mentioned. Contact Craig Tyler at [email protected] with further questions.

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December 4, 2019
Cold Weather Installation Tips Part 1 – Low-VOC Bonding Adhesives and Primers

As temperatures fall and winter approaches, specifying and handling building envelope products – especially adhesives and primers – becomes a concern. Low-VOC adhesives and primers contain more water than standard adhesives and primers and can be adversely affected by outside temperatures. When specifying a low-VOC bonding adhesive or primer for a winter installation time frame, make sure to include information in the specification regarding cold weather application. This should include heated storage enclosures, or "hot boxes", for jobsite adhesive storage. This practice is strongly recommended when ambient temperatures are expected to fall below 40°F for an extended period of time. Adhesives and primers should be stored in locations where temperatures are between 60°F and 80°F. While working with adhesives, they should be rotated in hot boxes to ensure the temperature of the product stays above 40°F. Adhesives may appear gelled or lumpy when left for extended periods of time at temperatures below 40°F. If this occurs, return the material to room temperature for a minimum of 24 hours prior to use. In all applications, but especially in colder conditions, make sure you achieve the proper coverage rates for the adhesive or primer being used. Following coverage rates for Low-VOC adhesives and primers allows proper flash-off and reduces the trapped solvents which could lead to membrane blistering. For applications in very cold temperatures, Flexible FAST™ Adhesive may be necessary. Flexible FAST is a two-part polyurethane foam adhesive which is spray-applied and used with a fleece-backed single-ply membrane. The advantage of this system is that it can be sprayed using 15- or 50-gallon drums of Part A and Part B, which can be heated using drum or band heaters. This allows the material to stay warmer during application and lowers the minimum application temperature to 25°F. So for your next cold weather specification of Low-VOC adhesives and primers, include some installation precautions as mentioned. Contact Craig Tyler at [email protected] with further questions.

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