A Sound Approach to Achieving the Best of Both Worlds

In building envelope designs calling for high levels of acoustic performance, there is often a potential trade-off between the conflicting requirements for controlling sound reduction and sound absorption. Sound reduction refers to the control of either internal or external noise in a building.

Typical applications include concert venues, where one is trying to avoid excessive noise levels from breaking out and buildings in areas near noisy facilities, such as airports, where one strives to achieve precisely the opposite. Sound absorption is the more common acoustic feature required by designers.

It is the control of attenuation, or internal reverberation of sound against building surfaces. A school sports hall is a very typical, everyday application requiring attention. Although most projects usually require one method of acoustic control, some still need to address sound reduction and absorption in the same envelope construction.

A typical example would be a concert venue situated close to or underneath a flight path of a major airport and with nearby residential properties. Decks are typically perforated to break up sound waves and assist absorption. However the perforated open area also allows sound to escape into the roof cavity, thus lowering reduction values.

There may also be requirements of a project where longer spans are required and  perforated deck  is unsuitable.

How, then, can these conflicting requirements be achieved at a minimal cost?

The answer is to install a plain deck with a  perforated under lining sheet, as indicated:-

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Installation of a D159 plain roof deck provides maximum spanning capability, whilst the addition of RL32/1000 perforated liner enhances absorption values with a 22% open area, and provides a more aesthetically pleasing finish. Sound is absorbed into the trough infill fillets, as for a perforated deck profile. This liner may be installed directly below the deck, or positioned under the beams to hide all support structure.

Comparison of ex works prices, based on 1000m2, indicate that there is no additional cost increase, for profiled elements, by offering an underlining system.

There would be costs for supporting zed spacers, additional fasteners and installation time. However the combined benefits of enhanced acoustic absorption, reduction and aesthetics will more than justify the modest additional expense.

Sustainable application of metal decking

As a 100% recyclable product, metal roof decking is the ideal choice when sustainability in construction is a key consideration. However, there are a number of other benefits to using metal decking in the construction of single-ply, standing seam or green roofs.

It’s incredibly strong for its weight, the fact that metal decking can span up to 12 metres allows building designers to lose much of the secondary structure.  Roof deck is fast to lay therefore reducing time on site and as large quantities can be bundled and loaded effectively, each lorry delivers a vast roof area, reducing the number of vehicles to site, not to mention all associated traffic, unloading and storage activities.  Roof deck  is a solution to the negative environmental impacts of a construction site – reducing noise, emissions, traffic congestion and more importantly our carbon footprint.

Energy use

These substantial sustainability benefits pale into insignificance, compared to the benefits gained over the life of a building, by utilising metal deck sustainable roof design. It is commonly accepted that the embodied energy in a building is approximately one tenth of the energy used in that building over a period of 50 years. The impact of including a highly insulated, well sealed metal deck roof can be a reduction in heat loss through the roof by half.

Green Roofs

However it’s not just about carbon and energy, metal deck green roofs offer far more than just that.

• Slows the run off. They reduce the amount of rain that runs off the roof and they slow down the peak rate of runoff by several hours, which in turn dramatically reduces flooding and the burden on the drainage system. The water is cleaned as it percolates through the layers.
• Habitat for wildlife. They cool the surrounding air as well as the building they are on and they provide a safe habitat for plants, bees, butterflies insects and birds.
• Feel good factor.  Green roofs look good in any work or home environment and encourage wildlife.
• Economics. Green roofs reduce the need for air conditioning and heating so they save money.
• Planning benefits. Many councils now insist on the inclusion of green roofs in building developments.

As a recent example, the UK’s largest and greenest sustainable storage facility at Adnams Brewery used a metal deck green roof with a Corus Panels and Profiles D159 under a Sky-Garden Greenroof to reduce the visual impact of the building on the landscape and to regulate the internal temperature. A drip irrigation system was installed to sustain the plants.