There’s little debate that material selection has a significant impact on roofing project outcomes. Choosing the right components, however, takes awareness of the available options. And when it comes to selecting cover boards, there are several reasons to consider a perlite solution, especially when hot systems are being considered.
Perlite 101
Perlite is a naturally occurring siliceous volcanic rock that takes the appearance of small, air-filled “bubbles” when crushed and super-heated. Perlite’s low weight, durability, and low thermal conductivity make it a popular material in many industrial applications, including roofing.
“It’s certainly a product with many advantages,” says James Kopaska, Product Manager at Johns Manville. “Perlite cover boards are a different product than wood fibre alternatives, so it’s difficult to make direct comparisons, but perlite certainly has attributes that make it superior in many applications.”
Certainly, perlite’s composition and weight make it an installer-friendly choice, but other factors make perlite cover boards a safe and reliable option.
Fire-resistant: Fires arising from torch-on installations are growing in frequency. What’s more, these incidents have spurred stricter regulations and insurance changes. As such, one of the most significant benefits of perlite cover boards are their fire-resistant properties. Compared to wood fibre cover boards, perlite alternatives boost a far lower flame index and will not sustain combustion.
Low absorption: When water gets into a roofing system during installation, it will find a way out. This can lead to gassing, membrane blistering, and other performance issues. A significant benefit of perlite cover boards, however, is that they have very low absorption properties, meaning they take in less water and less asphalt, thereby offering a more adhesive solution.
Cool under stress: Despite its light-weight nature, perlite material can take the pressure. During John Manville’s compression testing, for example, perlite cover boards have been shown to withstand significantly more pressure to deform by 10% (30 to 60 psi), compared to some wood fibre cover boards which state a 14.5 psi to deform by the same amount. This high-compressive strength provides a better substrate for the membrane and additional puncture and foot traffic resistance, which are desirable features for any membrane system.
Smoke development: Smoke isn’t always a welcome sight in more sensitive projects such as hospitals or schools. To that end, perlite material does not produce smoke during installation even when applied at higher temperatures. This makes them an ideal choice in projects where smoke reduction is key.
Eco-forward: Perlite is manufactured using perlitic aggregate and typically upwards of 40% recycled content which makes the board a more sustainable choice. This is different than wood fibre which relies on trees for the base production. Moreover, manufacturing waste can be easily fed back into the process.
Ease of installation, high fire resistivity, higher compression strength, lower moisture absorption, and low combustibility are some of the high-performance factors that make perlite cover boards a worthy consideration for roofing projects. And while the choice of materials will vary by each project, there is a benefit to recognizing what perlite can bring to the job.
Johns Manville premium perlite cover boards have been trusted by contractors, specifiers, and consultants since 1951. For more information, visit our Website.