IGUs. A sound acoustic solution?

sound and noise acoustic control with IGUsInsulating Glass Units (IGUs) or double glazing, have been a popular solution to control noise, but they aren’t the only, or even the best solution in many cases. The aim of this article is to explain how acoustic problems are identified, assessed and provide solutions to properly address them.

Acoustics

The acoustic performance of façades is becoming more important in building design, and not surprisingly is included as part of the Green Star rating process. Although it is a small part, it’s raising the profile of sound reduction and the need to find better solutions to the increasingly worsening noise problems in today’s society.

To better understand how to mitigate sound, it is beneficial to have an awareness of a few key ideas; how sound is transferred, the way different noises are measured, know about the principles to minimise the variety of sources and coordinating appropriate solutions. Prior knowledge makes finding a solution a lot quicker and easier when you are consulting a professional.  Using advice to compare test results, it is imperative to know the difference between glass only and window system results if you want sound acoustic solutions.

Determining sound factors

Noise sources in the vicinity of a project need to be identified to best determine the most efficient glazing solutions. Look for risk sources, some examples of which are below;

  • Traffic noise from vehicles – cars and/or trucks
  • Trains
  • Planes and flight paths
  • Trams
  • Boats
  • Entertainment venues
  • Industry – a warehouse, factory plant, a truck depot up the road

For each source, be aware of the proximity and direction it will be coming from.  Future changes that will affect sound transfer must also be considered – empty or older blocks that will be used for building development, planned roads and motorways to be constructed, or a feature that may be removed to expose the project to heightened noise distribution. This information will be assessed by an acoustic engineer or glazing contractor looking at the requirements of the project.

The two main properties that contribute to disturbance from noise are the frequency and intensity level at various frequencies, or volume. Both influence the selection of appropriate glazing systems for a project.

Frequency

Sound travels as sound waves (variations in pressure) that have different frequencies. When the sound wave hits an object, this will be absorbed, transferred or reflected dependant on the properties of the object and the frequency of the sound. Below is a table that describes the frequencies associated with different noises;

Frequency distribution

Volume

The inherent volume or loudness of noise is measured in decibels (dB). Following is a table that gives you an idea of how loud different noises are;

comparison of sound

 Acoustic fact:

The human ear cannot distinguish a change in noise level of 3dB or less.

Different types of glass will assist deadening the various frequency and sound levels. To decide what the best solutions are, the window systems need to be comparable.

Measuring how much a glazing system suppresses noise

The current standard unit that is used to nominate the amount of acoustic insulation achievable is the Rw. An Rw rating is applied to many products to compare its capability to reduce sound against similar products. However, the nature of glazing systems means that frequency plays a large part in the transference of sound. So correction factors are applied to the Rw and expressed as Rw(C, Ctr).

Using Rw Data results:

When looking at results, ensure you understand what the Rw rating applies to.  Glass only data will give you just that – a figure for the glass.  It will not be comparable with a whole of system framing. Glass only data has a higher figure, and misrepresents the effectiveness of the desired glazing solution.

Rw

The Rw, or weighted sound reduction index, is a material or system’s ability to reduce sound transferring through to the other side, of a window or wall. As a rough guide, an increase of 1Rw reduces the sound perceived on the other side by about 1dB.

Rw(C, Ctr)

The correction factor for the Rw takes frequency into account. Medium to high frequency noise like conversation, and faster traffic (travelling more than 80kmh) are nominated as the C number. Low to medium frequency sound like urban traffic and planes flying overhead are the Ctr figure.
If a project has a requirement of Rw = 32(-1,-4), then the Rw = 32, the Rw+C = 31 and the Rw+Ctr = 28. The noise frequency distribution determines the correction factor figure to be used. If the predominant noise source affecting a project is traffic noise, being a low frequency problem, the Rw+Ctr figure is used. In this case, the figure to achieve is 28. If a window system is rated at Rw30(-2,-2), the Rw+Ctr = 28, therefore achieving the above requirement. The Rw number should always be used with correction factors.

Testing the Acoustic Performance of Glazing Systems

Testing is done by accredited organisations in an acoustic laboratory. The testing space consists of two rooms of known acoustic properties separated by a wall with a high sound insulation. The rooms are constructed of thick block work with the entire laboratory sitting on airbags to isolate it from ground vibration. An opening is made in the wall for the glazing system. One of the rooms is set up as a source room, and one is the receiving room. The difference in noise level measured between the rooms is used to calculate Rw, C and Ctr figures that are attributed to the system tested.

Acoustic Solutions

There are several acoustic principles that are applied to the design of glazing systems to obtain the best performance to guide you in choosing the optimal glazing products.

Glazing design

Keeping sound out is like keeping water out – any gaps provide a path by which the acoustic efficiency of a system is reduced. Even the smallest crevice or notch out of a system makes a difference. Glazing systems can be riddled with gaps – good systems minimise these as much as possible. Testing is the only way to know how any system will perform.

Product selection

Restricting sound penetration is only as good as the barrier’s weakest point. Opening or operable parts of a façade are the hardest places to control sound, but improvements in technology are minimising the issue. With changes in door design to allow for access according to AS 1428, it is good to be aware these points are made weaker, acoustically.  With glazing developments, there are solutions to help minimise this issue.

Window systems with a positive closing force are more effective at blocking out sound. Awning windows and hinged doors generally perform better than sliding windows and doors.

Acoustic seals can be used to improve glazing performance and achieve a better Rw rating. The only way this can be accurately assessed and used for compliance, is if the glazing system is tested with the acoustic seals.

An air gap between the glass panels in a glazing system can provide a degree of sound reduction dependant on the size of the air gap. Typical IGUs with an 8, 10 or 12mm air gap, the improvement is marginal. Larger double glazed air gaps are much more effective, with 50mm being the “sweet spot” with only marginal improvement beyond this. These large air gap systems are generally the best performing of any glazing system.  Jockey sash systems can also be used to create large air gaps but have size restrictions and may cause internal condensation issues.

Laminated glass can provide equivalent or better performance than a standard air gap IGU. Typically the thicker the laminate, the better the acoustic performance. Specifically designed acoustic interlayers are now available that provide an increase in performance in standard interlayers

Looking for assistance with acoustic design

Window fabricators can help you understand the acoustic performance that their products provide. If you are aware of the nature of noise pollution in the vicinity of your project, then it’s a matter of matching the correct products to minimise this problem. Look for new technology becoming available to better deal with the increasing noise issues in today’s society.

When using window acoustic data, ensure you are discussing whole of window system data. There is a lot of glass only data available, but it’s the frame that is typically the weakest acoustic point of a glazing system. The glass only data will not give you a proper representation of noise control.

5 Points to Remember

  1. Understanding Rw(C,Ctr).
  2. Gaps in Systems = sound transfer. Minimise these weak points, especially in operable glazing.
  3. Larger air gaps in between glazing layers helps acoustically.
  4. Familiarity with latest technology in sound reducing products like acoustic seals and interlayers.
  5. Test results need to be comparable. Look at whole glazing systems, not glass only test results.

Helpful Links

For further information on the subject, please refer to the suggested following resources:

Capitol Apartments

The Capitol ApartmentsCapitol Apartments has been recently constructed at 35 Peel St, South Bank, Brisbane, QLD. It is a 10 storey building designed by Kowalski and built by TMF. This project is situated in the busy west side of South Bank, along some major traffic routes – one being Queensland Rail train tracks and rail bridge.  It is an ambitious project considering its location, and had very stringent guidelines to achieve before it was allowed to be constructed.

Strict Design Criteria

The main aspect of design took into account the proximity to the adjacent train line. Acoustics is an obvious problem, but the location of the railway tracks are within a stones throw, literally. As such, protection of the railway tracks from litter being thrown onto the lines is of critical importance. Accompanying this, the architects designed a building with many differing glazing requirements to achieve a cohesive up market residential property. This building is to be used as furnished apartments for long or short term accommodation for people in the South Bank area. With venues like Rydges and other large hotel names in the vicinity, a boutique, stylish result needed to be achieved. The Capitol Apartments The initial design phase required the windows to comply with acoustic standards, or the apartment would not get approval to be built. G.James were the only glaziers that could beat all the ratings required, and provide evidence via testing that these results were guaranteed. The design initially specified opening sizes to be built to, but to ensure quality, it was actually done as a measure and fit job. As such, the lead times were brought down dramatically in the manufacture and installation scheduling required to meet the builders time line, which G.James achieved.

Design Resolution

To accommodate the requirements to protect the tracks from litter, all windows to the railways (northern) elevation were fitted with fixed Crimsafe screens. The balconies are set up as an Alfresco area, and the Lismore designed version of the 445 sliding door system was used for the operable windows overlooking the tracks and the city, with a fixed light beneath. The Lismore design, allows the sliding door to be operated from the inside, allowing the Crimsafe screen to be fitted and fixed externally. This alfresco area also helps protect the interior from noise pollution. The Capitol Apartments Bedrooms were fitted with jockey sashes to provide an adequate acoustic barrier, and living spaces had IGUs (as well as the alfresco area) to protect it from railway traffic noise. Both use the 451 system. Some balconies also have 136 Double Hung IGUs incorporated into their design. Other areas use differing glazing suites including the 165 slider vents to wet areas, 265 awning windows, 651 shop front with IGUs in the gym on level 1 with a 476 hinged door.  The main entry was a 475 auto sliding door, and the 477-300 bi-fold system with a lowlight under in  650 framing are a suitable finish in the restaurant. All framing not done on the railway elevation used various types of SGUs to suit the look required. The Capitol Apartments We have released a project map to provide the location and a summary of works.  Keep an eye out for the Capitol Apartments on this map…

Project Update: Queensland Institute of Medical Research

QIMR Herston Rd Entrance

Transforming an existing medical research facility in Herston, QLD to align with the surrounding complex.

Queensland Institute of Medical Research Phase 3, or QIMR ph. 3, is the refurbishment of the Bancroft Centre. It is located just outside Brisbane’s CBD next to the Royal Brisbane Women’s Hospital.

The Bancroft Centre, owned by QIMR  is contracted to be built by Watpac. The project is designed by a joint architectural venture between Wilson and Wardle architects.

G.James’ Role

This project initiated as a design and documentation contract, in which G.James were required to advise and recommend the design of glazing works, survey the existing building and detail the information via formal drawings. Due to the positive contributions and coordination of this aspect of the project, G.James were awarded stage 2 – the supply and install of the glazing works.

The Bancroft Centre

The Bancroft Centre is a 14 storey concrete building with feature beams and columns criss crossing the building dividing up the individual windows and balconies spread across the elevations. At ground level, a large lobby window and sub station louvre is also part of the upgrade.

The medical research undertaken at the centre is highly sensitive. In the pursuit of the solutions being investigated, the building will be partially occupied by the client throughout the construction process. This will affect parts or entire floors at different stages. Close coordination of on site works, monitoring clients requirements and ensuring safety for all, dictates progress.

External Refurbish

The basic concrete structure remains, with the southern concrete face being removed and extended out towards Herston Road. The extensions are supported by a grid work of steel with concrete platforms. The face lift is to extend down the western side to the existing balconies and on the eastern side to the recently erected QIMR central building.

The architectural intent is to create a look that reflects the existing Clive Berghofer Cancer Research Centre (CBCRC) located on the other side of the QIMR central building. To do this:

  • The main façade on the curtain wall is being replicated as much as possible.
  • The visible rendered sheer walls are being covered with Alpolic cladding to wrap around to the front of the balconies and underside of the soffits in a similar fashion to the CBCRC building.
  • Glazing in the balconies and lobby were replaced to reflect the more natural colour scheme and full height layout of the CBCRC.
  • Louvres are being modernised and/or introduced to cope with the needs of the buildings updated research capacity, the design of which is in keeping with the other QIMR buildings.

G.James has followed stringent processing and approval of the glazing samples and design to ensure these principles are followed adequately.

Design: Energy and Acoustic Efficiency

Renovations on old buildings require them to be upgraded to meet the latest energy efficient guidelines. To accomplish this, the Bancroft refurbishment required higher performing windows than the original.  Another important design element to consider was that the Bancroft Centre is situated at what is now one of Brisbane’s busiest intersections.

Fronting onto Herston Road, a stones throw from Bowen Bridge Road, bus ways and the Inner City Bypass, shows the heightened necessity for acoustic protection.

The main curtain wall façade utilises the 651 series with highly efficient IGU’s made from Solarplus engineered glass with an acoustic laminate internally to assist with noise deadening. The visible features of the curtain wall replicate that of its neighbour providing a plaid pattern of greens and silver that provide the desired sister building effect.

The balconies use 450 framing with 475 door systems for the balconies’ hinged and sliding doors. A custom solution was introduced with laminated glass incorporating a thick 1.14mm acoustic laminate and energy tech inner lite working together for maximum efficiency and sound protection.

An environmental advantage to being involved in the design of the cladding, minimised the wastage by designing the cladding widths to suit what was commercially available. Approximately 85% of the panels could be made to their natural width.

Unusual Design Elements

The lobby or main entry spans a height of two stories. It has concrete features penetrating through the facade. This required some innovative design to incorporate these obstacles while maintaining the ability to replace the existing framing in a short turn around of a week. 650 framing was used in the lobby to achieve this.

The curtain wall is usually lifted into place by a mini crane positioned on the building.  It is dedicated to the curtain wall install.  On QIMR however, a tower crane had been fitted on site to accommodate phase 2 construction, and is also being used for phase 3.  This meant that fixing the curtain wall had to be timed in between other site deliveries and other uses required of the crane.

This has been a unique project with G.James contributing very early in the design process to assist in setting our the buildings requirements for our own and adjacent works. The achievements so far have culminated with smooth progression though out the project with the mutual assistance and close coordination between Watpac and G.James.

Looking ahead

G.James role at the Bancroft Centre is to be finalised approximately mid 2013, and the entire project to be competed by mid 2014. Tours of the QIMR facilities are available to the public. You can book a tour on the QIMR website.

Newington College – Sesquicentenary Building Project

The new curtain wall at Newington College

G.James has recently finished work on the Sesquicentenary Building Project at Newington College in Bankstown, Sydney. The bulk of this project comprises two new combined buildings – The Lawrence Pyke Science Centre and The Tony Rae Resources Centre Library. The project was designed by Budden Nangle Michael & Hudson Architects, and builder A W Edwards was contracted to construct it.

Foyer to the building.G.James’ work on the project comprised the design, supply and installation of windows, doors, curtain walls, glass walls, glass canopies, a glass greenhouse, aluminium cappings and soffits– utilising our 850-500, 651, 451, 475 and 476 Series frames. Jockey sashes from our 150 Series were required for most windows, and some windows also featured curved heads. G.James’ Sydney Commercial Façades division carried out the work on this project.

Noise Reduction

Acoustic laminate was used extensively throughout the project to minimise disruption to classes from external noise. Typically 12.76mm acoustic laminated glass was used externally and 10.76mm clear Low E coated ccoustic laminated glass was used internally in jockey sashes and internal skins. This was an important consideration as Newington College sits directly below the approach flight path into Sydney Airport with approaching aircraft flying very low directly above the school.

Curtain Wall Glazing

Curtain wall glazing.Four “curtain wall” sections were defined by the Architect and included in G.James’ scope of work. Two of these were fabricated as 850-500 Series structural glazed curtain walls. The Stair glazing used the 850-500 Series structural glazed frame as a window wall fitted between steel horizontal supports. Coloured back glass was used to infill between the frames and hide the steel. Jockey sashes and secondary frames were used behind these frames to create large cavities for acoustics. On one curtain wall an additional 850 Series frame was used as an internal frame to provide the nominated 400mm airspace.

Dual skinned Curtain Wall

The most prominent feature of the building is the final curtain wall  – pictured at the top of this post. This is a dual skinned arrangement with the outer skin built out from the building by a metre with three horizontal steel trusses. The glazed height of this wall is approximately 9.4m and is glazed with pieces of glass each approximately 4.7 m high by 2m wide – weighing a hefty 300Kg. This glass is supported by glazing channels top and bottom, and also by 15mm annealed glass fins vertically. The internal glazing skin comprises G.James’ 450 Series frame fitted with the flush face to the inside and incorporating jockey sashes fitted in-line with the fixed glass for access and maintenance. The metre wide cavity between the glass is ventilated and includes 600 mm wide horizontal and vertical automated tracking sun shades installed into this space by another contractor.

G.James has also supplied and installed soffit linings below this glazing, metre wide cappings over the cavity, and also to the other curtain walls. Several glazed awnings and a glazed greenhouse were also completed.

Official Opening

The buildings will be officially opened in July as part of the 150th anniversary celebrations at Newington College.

Aluminium conveyor rollers

High Tensile Tubes

Among our extensive range of aluminium extrusions, G.James produce a range of high-tensile strength aluminium extrusions for use as roller shells. Whilst not a new product for G.James, these have been subject to increased interest due to the growing mining industry – aluminium rollers can be an excellent choice for conveyor idlers in mining applications. They are available in a range of diameters –  4″, 5″, 6″ & 7″ (101.6mm, 127mm, 152mm, 178mm), and can be cut to short or long lengths as required.

Why Aluminium?

Aluminium roller shells result in significantly lighter rollers than those using steel shells. Their relative lightness means they require less power to run, and their reduced weight decreases the likelihood of strain injuries when being manually handled.  Aluminium is also corrosion resistant – a distinct advantage when dealing with corrosive materials such as coal or salts. Although steel is a harder material, aluminium still offers great wear resistance. All good things do however come to an end – even at their end of service life, aluminium rollers have the advantage of increased scrap value compared to alternative materials.

Manufactured to fine tolerances

Given the intended application, our roller shell extrusions are manufactured to extra stringent tolerances. Our roller shell extrusions are straight to within 1mm/3000mm, and typically offer a better TIR (total indicated runout – degree of roundness)  than steel rollers. This roundness helps to reduce noise – which is an advantage in already noisy environments where OH&S places an onus on noise reduction. Manufacturing tolerances for our range of roller shells are tabled below.

External Diameter (mm) Weight (kg.m)
101.60±0.40 2.681
127.00±0.40 4.492
152.00±0.40 5.894
152.40±0.40 6.275
152.40±0.40 7.478
178.00±0.40 8.876

  • External Diameter: Distance across the tube. (measurement 1 in the diagram above).
  • Max Ovality: Maximum distortion from round – ie. the variation between the tube at its thinnest and thickest measurements.
  • Wall Thickness: Distance from the exterior surface to the interior surface (measurement 2 in the diagram above).
  • Wall Thickness Eccentricity: Difference between the thickness of the tube at a given point & the thickness at the point opposite (ie. measurements A & B in the diagram).
  • Weight: Weight per metre of roller length.

Companies that use G.James for High Tensile Rollers

The following companies use G.James extrusions in their production of rollers:

Who to contact

For further information on our range of aluminium extrusions please peruse our online extrusion catalogue or contact Extrusion Sales on (07) 3877 2833.