Several ‘Sandwich’ Roof Assemblies Mitigate Sound Transfer

We all want a roof over our heads to protect us from the cold winter months, hot summer months and precipitation year round. How much thought goes into the sound-control construction of a roof, though? Have you considered the acoustic properties of your roofing system? Admittedly, acoustics is not a topic that many roofing contractors think about. The construction of a roof, however, can have a significant impact on the sound quality of the building interior. While this may not seem important in every project, it can be a critical element of the design for concert halls, theaters, auditoria and even school classrooms.

Sound Isolation

The acoustics of a space depend on many criteria, including sound isolation, sound reflection, impact noise and sound transfer. In many cases, particularly in noisy, urban environments, there is a need to prevent loud outside noises, such as traffic, sirens and airplane noise, from entering quiet spaces. Sound isolation depends on the entire envelope of a space, including external walls, windows and roofs.

Green roofs, particularly the “intensive” version, which includes several inches of heavier-weight soil, can provide effective sound control.

Green roofs, particularly the “intensive” version, which includes several inches of heavier-weight soil, can provide effective
sound control.

Historically, roofs over sound-sensitive spaces have been built with fairly dense materials, such as concrete, which by themselves are relatively effective in blocking sound transfer. As construction methods have developed, however, more lightweight construction is being used. If thought and care are not given to the assembly, these lightweight construction methods can cause serious issues with acoustics. Rain noise, mechanical noise and other exterior sounds can all transfer readily through a thin, lightweight roofing system.

In an effort to use lighter-weight construction, a “sandwich” assembly may be used to mitigate sound transfer. Similar to an Oreo cookie, a sandwich assembly’s outer layers are comprised of a heavy, dense material, and the inner filling consists of insulation and/or airspace. The materials of this assembly can differ from concrete to roofing board, rigid insulation to fibrous insulation, gypsum board to acoustic ceiling tiles. The components can be combined in a variety of ways, each with varying levels of sound isolation.

One of the principle phrases often heard when discussing sound isolation is “mass air mass”, which refers to the separation of two bodies of mass by an air space. The greater the mass and the deeper the air space, the more sound isolation will result. For this reason, a heavy mass, such as 5-inch concrete, followed by a deep air space, such as an 18- to 24-inch ceiling cavity in which ducts are run, followed by a continuous layer of drywall ceiling will provide a high level of sound isolation. Additional steps, like adding sound-absorptive material to the air space and/or using resilient connections when supporting drywall, further improves the sound isolation of the assembly.

Sandwich Roof Assemblies

Several sandwich roof assembly approaches are possible, including:

Good: Multiple layers of dense roofing board (at 2.5 psf per board, a final density of 10 psf or four-ply is often recommended) on either side of insulation, which ideally would be a sound-absorptive fibrous fill, like mineral wool, can reduce sound transmission. This approach is similar to a “floating floor”, often used in interior spaces to isolate sound transfer from one room to another. (Equivalent Sound Transmission Class, or STC, ratings can range from low 50s to low 60s, depending on whether a ceiling is included below the deck.)

Drywall ceilings hung on resilient hangers in conjunction with a lightweight roofing system provide even greater sound isolation by virtue of the resilient connection or “decoupling” of the drywall layer from the rest of the building structure.

Drywall ceilings hung on resilient hangers in conjunction with a lightweight roofing system provide even greater sound isolation by virtue of the resilient connection or “decoupling” of the drywall layer from the rest of the building structure.

Good: Green roofs, particularly the “intensive” version, which includes several inches of heavier-weight soil, can provide effective sound control. These can be part of a sandwich approach with airspace or rigid insulation between soil and a more-dense roofing material, similar to the roofing board described in the previous example. The mass-air-mass combination is similar to the approach just mentioned, and the benefits of green roofs appeal to many building owners for a multitude of reasons, including minimizing urban heat islands and storm-water management.

Good: A 5-inch slab of normal-weight concrete (150 pcf) has a density of 62 psf. This tried-and-true method is still used regularly and often proves to be the most cost-effective method of enclosing a space. The best sound isolation will occur if this is used in conjunction with a ceiling below, but on its own it still provides a reasonable level of isolation in many environments. This isn’t technically a sandwich system unless paired with a ceiling below or a green roof above. (Equivalent STC ratings can range from low 50s to low 80s. The highest ratings require pairing a resiliently hung ceiling with the concrete, as described under “Multi-function Roof Assemblies”.) IMAGES: Threshold Acoustics LLC [Read more…]

New Cool Roof Colors in Concrete Roof Tile Product Line

The Madera 900 Tahoe Blend, which is included in the Boral Concrete Roof Tile product line

The Madera 900 Tahoe Blend, which is included in the Boral Concrete Roof Tile product line

Boral Roofing unveiled its latest offerings in its Cool Roof portfolio during the recent International Builders’ Show (IBS) in Las Vegas.

The two Cool Roof colors making their debut at IBS 2014 are the Saxony 900 Slate Charcoal Blend and the Madera 900 Tahoe Blend, both of which are included in the Boral Concrete Roof Tile product line. These new colors have been designed to accommodate the updated California Code of Regulations, Title 24, Part 6. A major revision of the energy code involves new prescriptive Cool Roof requirements in select climate zones for low-rise residential steep-slope roofs. The change has resulted in a sizable increase in the aged Solar Reflective Index (SRI) for all roofing materials: from 10 to 16 or greater.

The new additions to Boral Roofing’s color portfolio ensure that Cool Roof requirements are met without sacrificing beauty or performance. The Saxony 900 Slate Charcoal Blend, which comes from Boral Roofing’s manufacturing plant in Rialto, Calif., perfectly complements the inherent beauty in French and Tudor architectural styles. Saxony Slate emulates the distinctive appearance of natural slate, while delivering the advantages of concrete tile. The Madera 900 Tahoe Blend, which is manufactured in Boral Roofing’s plant in Gilroy, Calif., offers an authentic replication of a hand-split cedar shake roof that is flexible enough to complement any architectural style. The award-winning Madera 900 is the most affordable, authentic hand-split wood shake replacement product available with all the benefits of concrete tile.

Boral Roofing’s latest Cool Roof technology is also being showcased via a rooftop display that demonstrates the real-time thermal performance of Boral Tile compared to other roofing materials. According to Oak Ridge National Laboratory, an independent testing agency, a family in a typical single-family house could save up to 22 percent per year on heating and cooling costs compared to the standard asphalt shingle roof.* A single family house with a Boral Cool Roof System could save an average of $15 to $20 per month immediately compared to a standard asphalt shingle roof, and, as energy rates rise year over year, savings could increase up to $20,000 over 30 years.**

Boral Roofing is the first clay roof tile manufacturer in the world to receive the prestigious Cradle-to-Cradle Gold Certification for environmentally sustainable products. Boral Clay Roof Tiles have a recycled content of up to 59 percent and come in an array of rich, kiln-fired hues with unrivaled color retention. Boral Concrete Roof Tiles contain no chemical preservatives and are up to 100 percent recyclable.

*Steep-slope Assembly Testing of Clay and Concrete Tile with and without Cool Pigmented Colors, Oak Ridge National Laboratory, 2005. Results vary based on profile of tile installed, location, weather and other factors.

**Results based on a 22 square roof in Southern California with no additional energy efficient upgrades during an average annual weather pattern, annual inflation rate of 3 percent, and annual energy cost increase of 3.5 percent. Savings may vary based on location, weather and other factors. Savings estimates are based on comparison to a similar size asphalt shingle roof.

Patch a Variety of Poured Roof Decks

SECUROCK Gypsum-Concrete Patch

SECUROCK Gypsum-Concrete Patch

SECUROCK Gypsum-Concrete Patch, formerly known as PYROFILL Gypsum Concrete, is a high-performing patch solution that delivers a professional finish on a variety of poured roof decks. It features more than 500 psi of compressive strength while its fast-setting properties enable foot traffic and fasteners within four hours of application.

  • Easy application to patch many different types of roof decks such as gypsum roof decks.
  • Mill-formulated and composed of specially calcined gypsum and wood chips or shavings.
  • Provides excellent fire performance – non-combustible in accordance with ASTM E136, and it’s fire rated and approved for use in UL Roof Deck Systems (P676, P503, P207, P229, P505, P507)
  • Manufactured to conform to ASTM C317, “Standard Specification for Gypsum Concrete”