The weather has an impact on everyone and every project.
There are weather-related design considerations to consider whether your project is in a region with 100-plus-degree temperatures, several feet of snowfall, or somewhere in between.
Designing a standing seam metal roof based on the weather it will experience helps make sure the roof doesn’t break down or fail too soon because of the environment. Furthermore, it safeguards the property owner’s or client’s often significant investment.
This article will cover some of the most important considerations for warm and cold weather climate design. Before we start, you might want to read through the list of things to consider when designing for hot and cold weather. This could help make sure that all design angles are taken into account.
Considerations for Metal Roof Design in Warm Weather Climates
Cool Metal Roofing System
Installing a cool metal roofing system is one of the first main design considerations for a property exposed to extreme heat.
Cool metal roofing refers to painted or coated metal products that reflect sunlight to dissipate heat. Cool roofing ensures heat is adequately transferred from the metal’s surface, allowing the cooling system to use less energy to keep the indoors at a comfortable temperature. According to the Green Building Alliance (GBA), installing cool roofing can result in a 7% to 15% reduction in total cooling energy costs.
Despite popular belief, cool metal roofing is not a specific type of metal; rather, the “cool” properties depend on the paint system used during the coating process. Innovative solar reflective pigments are used in the cool metal roofing paint/resin formula.
You should also ensure that the metal has the following:
- Solar reflectance
- Solar Reflectance Index
UV Exposure Protection
Another critical aspect of installing a metal roof in a warm climate is selecting metal products coated in a paint system that can withstand excessive UV exposure.
Unfortunately, fading is to be expected on a metal roof, especially if it is consistently exposed to the sun and high temperatures. However, this does not imply that the fading or degradation of the metal’s paint system must be excessive.
You should choose or specify metal with one of the following paint finishes:
- Polyvinylidene fluoride (PVDF)
- Silicone-modified polyester (SMP)
Reading the warranty documents is one of the best ways to determine how long the manufacturer expects the paint system to last, especially when exposed to UV. This includes all inclusions, exclusions, and other special circumstances. Most reputable manufacturers put their paint specs online so you can see how the coatings worked when they were tested in harsh weather.
Installing a fire and combustion-resistant roofing material is critical in areas where hot and dry weather conditions can lead to fires. Building with fire-rated materials can help prevent buildings from catching fire and spreading to other structures.
When it comes to standing seam metal roofing, look for metal that has been tested under the UL 790 standard and has a Class A (the best/highest fire rating). “Roof coverings are effective in severe fire tests,” a Class A rating means. Roof coverings of this class provide a high level of fire protection to the roof deck under such conditions, do not slip from position, and are not expected to produce flying brands.”
Uplift Resistance, Hail Resistance, and Location-Specific Codes Have All Been Tested
Along with being resistant to fire, a standing seam roof system needs to be tested to ensure it can withstand weathering events that can damage a roof. In hot weather, this can include wind (hurricanes, tropical storms, tornadoes, and so on), hail, and rain (wind-driven rain). Furthermore, you may live in a state, county, or municipality with regional codes and testing requirements.
Let’s take a closer look at some extreme weather events and the testing standards to determine if your project is in an area where it might occur.
Wind and Wind Uplift Testing (UL 580 & UL 1897)
Standing seam metal roofing assemblies tested to UL 580 are ideal for properties where hurricanes, tornadoes, and other high-wind events are a risk. This standard assesses the wind uplift resistance of a metal roofing system, which includes the panels, accessories (fasteners, clips, and underlayment), and structural support frame. The test applies positive and negative pressure and is a pass or fail test conducted in three UL 580 sequences; if the system can exceed Class 90, it is then subjected to a UL 1897 test until it fails:
- UL 580 Class 30
- UL 580 Class 60
- UL 580 Class 90
- UL 1897 test
Hail & Impact Resistance Testing (UL 2218)
In areas where hail is a concern, always ensure that the roof system you install complies with the UL 2218 industry standard. This test determines how resistant a metal panel is to being punctured or failing when it comes into contact with hail or other small debris.
The final classification ranges from Class 1 to Class 4, with Class 4 being the most durable and least likely to fail when in contact with objects.
Rain And Water Intrusion Testing (ASTM E1646) / Wind-Driven Rain Testing (TAS 100)
ASTM E1646: In warmer climates with heavy rainfall, choose a panel system with a passing ASTM E1646 water penetration rating. After reaching the predetermined air pressure, water is sprayed on the panels for 15 minutes. After determining the volume of ponded water, the amount of water infiltration through the panel is measured. This is a pass-or-fail test in which any water entry into the system will fail.
TAS 100: TAS 100 is a less common rain-related test standard that measures how a roof system performs in the wind and wind-driven rain conditions. TAS 100 is a region-specific test that varies significantly from project to project. Check the building codes in your area to see if this test is required.
Proximity to the Coastline or Large Body of Water
Another factor to consider in warm-weather environments is the property’s proximity to water, particularly a coastline or saltwater environment. All properties located within a certain distance of a saltwater-containing coast should use an engineered aluminum roof system rather than a Galvalume system. Aluminum can withstand saltwater corrosion and rusting better while providing a substantial paint warranty.
Considerations for Metal Roof Design in Cold Climates
Snow Shedding And Retention Systems
In areas where cold weather is typical, snow is by far one of the most significant property concerns. When it comes to snow accumulation on a roof, the primary concern is the safety of those who live in, enter, and leave the building. Furthermore, you want to minimize any damage that falling snow can cause to the property below, such as windows, doors, cars, plants, etc.
This is why it is critical to design your roof system with the proper snow-shedding or retention system for your roof.
In regions where snow accumulation is a threat, roofs should always be designed with a steeper pitch or slope that allows for snow retention over doorways, walkways, garages, and other areas where people and property can be damaged.
Several snow retention systems to choose from are warranted and match the design of a roof. In addition, snow retention and shedding systems can be installed without ever penetrating the surface of the roof, which is always recommended for standing seam metal roof systems.
Ice Dam Prevention
Another concern in cold climates is the possibility of ice dams forming on the roof’s eave. Fortunately, ice damming is less likely to occur if you use a standing seam metal roof for your project.
Standing seam metal roofs, a type of metal roofing, are designed to allow water to run freely off their surface, reducing the likelihood of ice dam formation. Furthermore, in some cases, you can completely avoid the formation of ice dams by ensuring that your entire roof system has proper ventilation.
Furthermore, if ice damming is a concern, always use an ice and water shield type of underlayment beneath the panels. This will help to keep water out of the structure.
Underlayments Designed for Cold Weather
When it comes to the underlayment, there are several factors to consider, especially in colder climates.
Ice & Water Shield Underlayment (h3)
To begin, we recommend using a full ice and water shield underlayment, a waterproof membrane product that protects vulnerable roof areas from water and ice damage. Valleys, eaves, hips, penetration points, and any other roof area susceptible to water or ice intrusion are examples of such areas.
If you use synthetic underlayment, the roof pitch should be at least 3/12. Nonetheless, we recommend using an ice and water shield in conjunction with the synthetic in the aforementioned vulnerable areas.
Many underlayments have minimum outside and surface temperatures that must be met in order for them to be installed appropriately. For instance, ice and water shield products have a peel-and-stick adhesive backing that risks not adhering to the roof deck if installed at temperatures below 40 degrees.
Always double-check the minimum installation temperature and any other temperature constraints that may affect your underlayment choices.
Slope & Substrate Requirements
Always check the minimum slope requirement for the underlayment you specify, regardless of the environment. Some underlayments, including ice and water shield, may not go as low as you think. It is critical to read and follow the manufacturer’s instructions.
The same goes for ensuring that your project can use the underlayment on the roof deck substrate. Not all underlays are suitable for metal decking (B-deck), concrete, etc., but most can be installed over plywood or OSB decking.
Proper Structural Support
Another essential safety measure to consider when it comes to roof snow buildup in colder areas is having the proper structural support underneath the standing seam metal roof.
People often forget that snow is water and that water is heavy. So, when designing a building’s roof, ensure it has enough snow load capacity to handle the weight of water and snow. This is true if you have a system that keeps snow on the roof, allowing it to run off safely over time.
If you want to ensure the structure can withstand the weight, it’s best to work with a structural engineer.
Proximity to the Coastline or Large Body of Water
The same principles apply to cold-weather coastal properties to hot-weather metal roofing concerns. Any property located within these coastal saltwater distances should install an engineered aluminum roof system rather than a Galvalume system:
- Within 400 ft of a coastline with a marsh
- Within 800 ft of a coastline with a large bay
- Within 1500 feet of a coastline with breaking surf
Final Thoughts on Metal Roofing and Weather
Weather can significantly impact your design projects that use a standing seam metal panel system. However, if you know what to look for based on your location and weather patterns, you’ll be well-equipped to design a long-lasting metal roof that will satisfy you and your client.