High-Temperature (HT) Underlayment for Metal Roofs: Debunking the Myth

Facts and Logic Work Against the Popular Belief, Metal Roofs Do Not Actually Require High Temp (HT) Underlayment

At TUFFDRY, we pride ourselves on producing top-quality products and maintaining transparency with our customers. As a manufacturer dedicated to looking out for the best interests of roofers, we understand the importance of making informed decisions. This article delves into the facts and research surrounding high-temperature (HT) underlayment after deep investigation and discussions with many metal roofing manufacturers. While we encourage all roofers to conduct their own research, we want to share what we've uncovered. Lets review some facts.

Typical Roof Temperature Ranges

When metal roofs first came on the market, they were recorded to reach temperatures as high as 190°F in the harshest environments. While this is certainly hot, it is important to consider the advancements in reflective coatings and paints over the last 10 years, which have been widely adopted and, in many states, are required. These treatments can reduce the temperature of metal roofs by as much as 50°F, making metal roofs cooler than traditional oil based, black asphalt shingles, which can reach a scorching 168°F.

Standard High-Quality Peel-and-Stick Underlayment: Products like those from TUFFDRY can withstand temperatures up to 240°F (116°C) for prolonged periods. They also offer 180 days of UV protection when "drying in" a roof before the final roofing material is installed and come with a 30-year warranty.

High-Temperature Underlayment: These can endure temperatures up to 260°F (127°C) or higher. However, this increase in temperature tolerance—only about 7% more than standard underlayments—comes at a significant cost.

Given that the hottest a metal roof typically gets is around 190°F, standard high-quality peel-and-stick underlayment rated for 240°F appears more than sufficient. This temperature capability already provides a significant buffer above the maximum expected roof surface temperature.

Understanding HT Underlayment

High-Temperature (HT) underlayments are widely available in the marketplace, with most major manufacturers offering these products as part of their roofing solutions. These HT underlayments are produced by adding additional, expensive additives to the formulation, which enables the material to withstand higher temperatures. Specifically, these modifications increase the maximum temperature rating from 240°F to 260°F—only about a 7% increase in heat tolerance. However, this minor enhancement comes at a significant cost. According to industry pricing data, the inclusion of these additives drives the cost of HT underlayments up by an average of 120% or more compared to standard underlayments.

This raises a crucial question: Is this substantial price increase justified when the maximum recorded temperature for metal roofs in the harshest environments is only 190°F? Despite the marketing push for HT underlayments, there is a lack of evidence suggesting that such extreme temperature resistance is necessary for most metal roofing applications. As Roofing Contractor Magazine notes, “The cost-benefit ratio of HT underlayments often does not align with the actual thermal demands of metal roofs, which rarely exceed the capabilities of high-quality standard products.” This discrepancy suggests that while HT products are available, their necessity is questionable, especially when considering the significant cost increase for a relatively small gain in temperature tolerance.

Why Consider HT Underlayment?

Despite the apparent sufficiency of standard underlayments, HT underlayment is often marketed as a necessary upgrade. Let's explore the validity of this claim:

Perceived vs. Actual Need:

* Temperature Margins: Standard underlayment rated for 240°F already exceeds the highest recorded temperatures for metal roofs, providing a comfortable safety margin well above the maximum recorded metal roof temperature of 190°F.

* Metal Roofs vs. Asphalt Shingles: Metal roofs can actually be cooler than asphalt shingles because metal reflects more sunlight and cools down faster after sunset. This undermines the notion that metal roofs inherently require HT underlayment due to higher temperatures.

Quality and Durability of Standard Underlayment:

* Prolonged Heat Resistance: High-quality peel-and-stick underlayments like those from TUFFDRY are engineered to withstand prolonged high temperatures up to 240°F. This durability is sufficient for metal roofs even in extreme climates.

* UV Protection and Warranty: With 180 days of UV protection during the construction phase and a 30-year warranty, these products offer robust performance guarantees that cover the critical aspects of roof protection and longevity.

Marketing Perceptions:

* Marketing Gimmick: The push for HT underlayment can be seen as a marketing strategy that preys on the perception that metal roofs are exceptionally hot. In reality, with appropriate reflective coatings and ventilation, metal roofs can perform as well as, or better than, other roofing materials in terms of heat management.

Cost-Benefit Analysis

Given that high-quality standard underlayments can effectively manage the temperatures associated with metal roofs, the additional cost of HT underlayment may not be justified:

* Standard Underlayment Sufficiency: Products rated for 240°F with extensive UV protection and long-term warranties provide ample protection without the need for HT variants.

* Economic Efficiency: Opting for standard underlayment can reduce costs without compromising the performance and safety of the roofing system.

Conclusion

In many cases, high-quality standard peel-and-stick underlayment rated for 240°F is more than sufficient for metal roofs, especially considering modern advancements in underlayment technology. Products from companies like TUFFDRY offer prolonged temperature resistance, UV protection, and long warranties, ensuring excellent performance and durability.

The promotion of HT underlayment can often be a marketing tactic leveraging misconceptions about metal roof temperatures. Metal roofs, in fact, can be cooler than asphalt shingles due to their reflective properties. Therefore, homeowners and builders should carefully assess their specific roofing needs and consider the substantial benefits of high-quality standard underlayments before opting for the more expensive HT options. By making informed decisions, they can achieve optimal roofing performance while managing costs effectively.

Additional Considerations: Nail Down Synthetic Underlayment and Long-Term Implications

While standard high-quality peel-and-stick underlayment may be more than sufficient under metal roofs, it's worth considering the benefits of high-quality nail-down synthetic underlayment, such as TUFF150, as an excellent alternative. States like Florida, for example, recognize the validity of using two layers of nail-down underlayment as a viable roofing solution under the Florida Building Code.

One potential long-term issue with full-roof peel-and-stick application is that it can fuse into the CDX plywood over time. This becomes problematic if the underlayment needs to be replaced in the future, as it could lead to the need for costly repairs to the CDX itself. This is a significant concern since many insurance companies cover the replacement of only the tiles and underlayment in the event of weather damage—not the CDX, which could become a major financial burden if it has fused with the peel-and-stick material.

Moreover, some installers apply peel-and-stick over nail-down underlayment, which defeats the purpose of the peel-and-stick product. Peel-and-stick underlayment needs direct contact with the CDX or OSB to perform optimally. Instead of applying peel-and-stick across the entire roof, it might be better to consider using granulated ice and water peel-and-stick underlayment strategically in vulnerable areas, such as eaves, rake edges, overhangs, and valleys, while using a quality nail-down synthetic underlayment like TUFF150 for the remainder of the roof. This approach ensures maximum protection where it's most needed while preventing the long-term issues associated with full-roof peel-and-stick application.

At TUFFDRY, we pride ourselves on producing top-quality products and maintaining transparency with our customers. As a manufacturer dedicated to looking out for the best interests of roofers, we understand the importance of making informed decisions. This article delves into the facts and research surrounding high-temperature (HT) underlayment after deep investigation and discussions with many metal roofing manufacturers. While we encourage all roofers to conduct their own research, we want to share what we've uncovered.

Typical Temperature Ranges and Underlayment Capabilities

Metal Roof Temperatures: Metal roofs have been recorded to reach temperatures as high as 190°F in the harshest environments. While this is certainly hot, it is important to consider the advancements in reflective coatings and paints, which have been widely adopted and, in many states, are required. These treatments can reduce the temperature of metal roofs by as much as 50°F, making them even cooler than traditional black asphalt shingles, which can reach a scorching 168°F.

Standard High-Quality Peel-and-Stick Underlayment: Products like those from TUFFDRY can withstand temperatures up to 240°F (116°C) for prolonged periods. They also offer 180 days of UV protection when "drying in" a roof before the final roofing material is installed and come with a 30-year warranty.

High-Temperature Underlayment: These can endure temperatures up to 260°F (127°C) or higher. However, this increase in temperature tolerance—only about 7% more than standard underlayments—comes at a significant cost.

Given that the hottest a metal roof typically gets is around 190°F, standard high-quality peel-and-stick underlayment rated for 240°F appears more than sufficient. This temperature capability already provides a significant buffer above the maximum expected roof surface temperature.

Understanding HT Underlayment

High-Temperature (HT) underlayments are widely available in the marketplace, with most major manufacturers offering these products as part of their roofing solutions. These HT underlayments are produced by adding additional, expensive additives to the formulation, which enables the material to withstand higher temperatures. Specifically, these modifications increase the maximum temperature rating from 240°F to 260°F—only about a 7% increase in heat tolerance. However, this minor enhancement comes at a significant cost. According to industry pricing data, the inclusion of these additives drives the cost of HT underlayments up by an average of 120% or more compared to standard underlayments.

This raises a crucial question: Is this substantial price increase justified when the maximum recorded temperature for metal roofs in the harshest environments is only 190°F? Despite the marketing push for HT underlayments, there is a lack of evidence suggesting that such extreme temperature resistance is necessary for most metal roofing applications. As Roofing Contractor Magazine notes, “The cost-benefit ratio of HT underlayments often does not align with the actual thermal demands of metal roofs, which rarely exceed the capabilities of high-quality standard products.” This discrepancy suggests that while HT products are available, their necessity is questionable, especially when considering the significant cost increase for a relatively small gain in temperature tolerance.

Why Consider HT Underlayment?

Despite the apparent sufficiency of standard underlayments, HT underlayment is often marketed as a necessary upgrade. Let's explore the validity of this claim:

Perceived vs. Actual Need:

* Temperature Margins: Standard underlayment rated for 240°F already exceeds the highest recorded temperatures for metal roofs, providing a comfortable safety margin well above the maximum recorded metal roof temperature of 190°F.

* Metal Roofs vs. Asphalt Shingles: Metal roofs can actually be cooler than asphalt shingles because metal reflects more sunlight and cools down faster after sunset. This undermines the notion that metal roofs inherently require HT underlayment due to higher temperatures.

Quality and Durability of Standard Underlayment:

* Prolonged Heat Resistance: High-quality peel-and-stick underlayments like those from TUFFDRY are engineered to withstand prolonged high temperatures up to 240°F. This durability is sufficient for metal roofs even in extreme climates.

* UV Protection and Warranty: With 180 days of UV protection during the construction phase and a 30-year warranty, these products offer robust performance guarantees that cover the critical aspects of roof protection and longevity.

Marketing Perceptions:

* Marketing Gimmick: The push for HT underlayment can be seen as a marketing strategy that preys on the perception that metal roofs are exceptionally hot. In reality, with appropriate reflective coatings and ventilation, metal roofs can perform as well as, or better than, other roofing materials in terms of heat management.

Cost-Benefit Analysis

Given that high-quality standard underlayments can effectively manage the temperatures associated with metal roofs, the additional cost of HT underlayment may not be justified:

* Standard Underlayment Sufficiency: Products rated for 240°F with extensive UV protection and long-term warranties provide ample protection without the need for HT variants.

* Economic Efficiency: Opting for standard underlayment can reduce costs without compromising the performance and safety of the roofing system.

Conclusion

In many cases, high-quality standard peel-and-stick underlayment rated for 240°F is more than sufficient for metal roofs, especially considering modern advancements in underlayment technology. Products from companies like TUFFDRY offer prolonged temperature resistance, UV protection, and long warranties, ensuring excellent performance and durability.

The promotion of HT underlayment can often be a marketing tactic leveraging misconceptions about metal roof temperatures. Metal roofs, in fact, can be cooler than asphalt shingles due to their reflective properties. Therefore, homeowners and builders should carefully assess their specific roofing needs and consider the substantial benefits of high-quality standard underlayments before opting for the more expensive HT options. By making informed decisions, they can achieve optimal roofing performance while managing costs effectively.

Additional Considerations: Nail Down Synthetic Underlayment and Long-Term Implications

While standard high-quality peel-and-stick underlayment may be more than sufficient under metal roofs, it's worth considering the benefits of high-quality nail-down synthetic underlayment, such as TUFF150, as an excellent alternative. States like Florida, for example, recognize the validity of using two layers of nail-down underlayment as a viable roofing solution under the Florida Building Code.

One potential long-term issue with full-roof peel-and-stick application is that it can fuse into the CDX plywood over time. This becomes problematic if the underlayment needs to be replaced in the future, as it could lead to the need for costly repairs to the CDX itself. This is a significant concern since many insurance companies cover the replacement of only the tiles and underlayment in the event of weather damage—not the CDX, which could become a major financial burden if it has fused with the peel-and-stick material.

Moreover, some installers apply peel-and-stick over nail-down underlayment, which defeats the purpose of the peel-and-stick product. Peel-and-stick underlayment needs direct contact with the CDX or OSB to perform optimally. Instead of applying peel-and-stick across the entire roof, it might be better to consider using granulated ice and water peel-and-stick underlayment strategically in vulnerable areas, such as eaves, rake edges, overhangs, and valleys, while using a quality nail-down synthetic underlayment like TUFF150 for the remainder of the roof. This approach ensures maximum protection where it's most needed while preventing the long-term issues associated with full-roof peel-and-stick application.