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Gaining traction is a hybrid roofing system combining Roxul TopRock DD Plus stone wool insulation board with a layer of polyisocyanurate foam plastic. This relatively new assembly achieves a high-performance roof at competitive cost to a traditional two-layer polyiso system with coverboard.
Roxul TopRock DD Plus is a rigid, dual-density stone wool insulation board with a bitumen-coated rigid upper surface for durability and enhanced strength. Designed for commercial and industrial low slope roof insulation applications, TopRock DD Plus is suitable for new building and re-roofing applications and is intended for use with torch, hot-mopped or self-adhered membranes. In addition to being moisture, fire and sound resistant, TopRock DD Plus is dimensionally stable, non-corrosive and offers high impact resistance. It delivers an R-value of 3.8/inch in thicknesses of 2 to 6 inches.
In addition to allowing for reduced layers and labor, a hybrid roofing system incorporating TopRock DD Plus stone wool insulation board with a layer of polyisocyanurate offers a number of clear advantages:
Thermal stability: TopRock DD Plus allows designers to keep the lower polyiso layer’s temperature closer to the designed thermal gradient, leading to greater occupant comfort and better overall energy efficiency. With lower heat flux measurements, interior temperatures and cap sheet surface temperatures than polyisocyanurate, TopRock DD Plus helps decrease peak membrane temperatures which is also thought to slow the deterioration of the membrane.
Preserving R-value: A hybrid roofing system is more effective at addressing the issue of climate-driven R-value, with stone wool offsetting the drop in thermal performance experienced by polyiso at lower temperatures. See Information sheet 502, Building Sciences Corp., 2013 for more info.
Greater dimensional stability: Unlike polyiso, stone wool products remain dimensionally stable and virtually unaffected by expansion and contraction as a result of temperature fluctuations, ultimately resulting in greater long-term thermal resistance. Stone wool is also moisture resistant, further contributing to exceptional stability which eliminates stresses on the roofing membrane and extends the overall service life of a roof.
Excellent Sound Absorption: Sound absorption is another important consideration roofing system designers must take into account. Factors such as metal roofs, HVAC units, and close proximity to airports and schools will necessitate using products with excellent sound reduction properties. In fact, building codes in some local municipalities require builders to meet strict acoustic specifications. Using TopRock DD Plus over foam plastic insulation can increase a roof assembly’s sound absorbency considerably, due to stone wool’s density and multi-directional fiber orientation.
Increased Fire Safety: Fire safety and the building codes enacted to protect occupants remain of paramount importance in building design and construction. Roofing assemblies are a component worthy of consideration in a building’s overall fire protection plan. Fire resistant materials, like TopRock DD Plus stone wool, that do not add fuel to an existing fire or contribute to toxic smoke and harmful gases, are optimal. Installing stone wool insulation over foam plastic insulation can provide valuable safety benefits.
“Stone wool commercial roofing products like Roxul TopRock DD Plus check many of the boxes that architects, designers, specifiers and owners look for when it comes to a quality roofing system,” explains Andrew Lindley, Segment Manager, Building Insulation - Roofing, Roxul Inc. “The beneficial qualities of TopRock DD Plus contribute to a hybrid roofing system that is resilient, energy-efficient and environmentally conscious. As part of a hybrid system, it offers excellent component compatibility, impact resistance, compressive strength, as well as moisture resistance and dependable thermal performance in real world conditions.It’s those top line benefits that are behind the growth in hybrid roofing system installations.”
A hybrid roofing system combining high-performance Roxul TopRock DD Plus stone wool insulation with the advantage of polyiso’s higher R-value per square inch provides a competitive option for designers looking to achieve reliable results in an industry of evolving demands and choices.
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posted: 9/7/2016
