Bushfire Risk, Assessment and Glazing Solutions

Australia has a love hate relationship with bushfires. It has been so much a part of the natural history here it has become an endemic part of existence; without bushfire certain plants wont propagate, although the rest of anything living, fears it. It’s just one of the many parts of the Australian lifestyle that needs to be taken in a serious light – and be prepared for.

Assessing Bushfire Risk

There have been major developments in ways to protect in the case of bushfire – from household escape plans, to continuing technology in fire fighting strategies and more recently since dramatic fire events, building design. Australian Standards have developed AS 3959, and as part of that, a system that determines your Bushfire Attack Level or BAL. In the BAL, it gives a provision for products in the building industry to be rated according to their resistance to bushfire attack.

The BAL rating for your situation can be determined by referring to AS3959 or guides provided by your local services. NSW Rural Fire Service has a comprehensive user guide as an Application Kit to the BAL for reference. You will attain one of six rated categories. Your risk is assessed by looking at type and proximity of vegetation, and the slope of the land your property is on. Your calculated BAL rating is used to select building products. Products will be rated with the same figures, offering protection for that level of BAL rating.

BAL Rated Glazing Options

G.James Glass & Aluminium has developed a BAL manual to guide people through making the right decision when looking at glazing products. It outlines the G.James glazing suites that should be used for buildings in the following high risk categories:

  • BAL 19
  • BAL 29
  • BAL 40

The G.James BAL manual outline the glazing system, glass type, hardware, gaskets and mesh requirements for the individual systems according to your BAL rating. As an example, if you have a rating of BAL 29, and need a double hung window, we will suggest you use the following:

The 136 Series Double Hung Window with a minimum of 5mm toughened glass, standard mohair, glazing vinyls and other hardware, and external screens require a fire retardant spline with aluminium or steel mesh with an aperture of less than 2mm. This is an example only, and you need to confirm details with G.James staff that can ensure these are the products you need for your individual situation.

Your selection of glazing should not be limited. G.James have BAL glazing solutions for sliding doors, louvres, double hung windows, fixed windows, hinged doors, bifold doors, awning windows, casement windows and sliding windows. When you talk to G.James personnel, they can guide you through the options.

Requirement for Buildings

There is no requirement to alter existing building materials, but if you plan on building or renovating, you will need to implement the recommendations of the the BAL report. It is a wise idea to be aware of the rating your property would get even if you aren’t looking at building in the near future. Finding out the weak points, you can make minor adaptions to the building materials or surrounding vegetation to give yourself a better chance in case fire ever threatens your neighbourhood.

Be aware of the different ways you can keep knowledgeable about risks in your area. Know your local brigade and SES, having their contact details on hand. Check your states fire services for more information.

During recent fire incidents when the heat was on, communication became difficult due to cut lines, and websites being bombarded and going down. The NSW Rural Fire Service had a great system of reporting regular updates on their face book feed. Know where to keep up to date on the latest details and leave emergency lines free for those that require it.

Be prepared and stay safe.

Glass By Definition – Part 1

Glass Bike - Glass Definitions - G.James Glass and AluminiumThis article will assist in demystifying the types of architectural glass used in buildings. The names we use for the different glass types are generally attributed to some part of the manufacturing process. In part one of this two part series, we look at basic glass products to highly processed glazing options.

Some History on Architectural Glass

Since clear glass was being first made in about 100 CE, in Alexandria, the Romans began using it architecturally. This began the long list of manufacturing methods and specialised names attributed to the different types of processes – Broad sheet, Crown, Polished Plate, the list goes on. In 1848, a crude form of float glass was patented by inventor Henry Bessemer by pouring glass onto liquid tin, but it was very expensive. It wasn’t until 1959 that this idea for float glass was made in a practical method – a discovery by Sir Alistair Pilkington that now dominates the worldwide commercial production of architectural glass products.

Basic Float Glass Products

The differences between the basic glass types are formed in the glass making “float process”. Soda, lime and silica as well as broken glass called cullet are the major components used in the manufacture of glass. These components are mixed into a batch before being heated to approx. 1500°C in a furnace. The molten glass is then floated on a “tin bath” –  a layer of molten tin.   As the glass begins to cool it solidifies and is drawn out of the float tank in one continuous ribbon.  The glass enters the annealing or cooling lehr – it is the controlled cooling (annealing) of the glass that allows it to be cut and further processed.

Float Glass or Annealed Glass

These terms are interchangeable and refer to the respective glass manufacturing processes.  They describe glass in its basic form, before secondary manufacture.  In a general sense, Annealed Glass is used when comparing heat treated glass to non heat treated glass.

Clear Glass

Clear Glass is a piece of transparent float glass, typically uncoloured.

Tinted Glass

Tints are glass with metal oxides added to give it a specific hue. The tint or colouration is through the body of the glass and therefore darkens with an increase in thickness.  Apart from aesthetics, tinted glass is used for reducing heat gain through the glazing system. Common tints include green, blue, grey and bronze.

Super Tints

Super Tints are designed to reduce heat gain while allowing the maximum amount of light through making it a performance product. The heat absorbing qualities also make them prone to thermal stress (caused by temperature difference), and a thermal safety assessment is recommended to determine if heat treating is required (see Secondary Manufacture below). Colours include Azuria, Super Green and Super Blue.

On Line Coated Glass

Sometimes referred to as pyrolytic glass, metallic oxides are deposited onto the glass surface in the float glass tank during manufacture. These coatings can increase the performance of the glass with a range of reflective and low E products available. They are extremely hard and durable, and can be used on their own or heat treated without affecting the coating.

Low Iron Glass

The green colouration in glass is due to the iron content found in silica or sand. Low Iron Glass has less than 1/10th of the iron content of standard glass and are considered ultra clear. Low Iron Glass is ideal for use in display cases, painted glass applications like splash backs or in areas where high clarity is required.

Deli Bend or Curved Glass (Annealed)

Glass can be curved as float, by laying the glass over a mould before annealing begins. It is commonly used to make butcher or delicatessen benches (hence the name), furniture and curved architectural glass that is to be laminated.

Processed Glass

Glass requires finishing before it can be used in location, or sent for secondary manufacture. Commonly, this includes cutting to size, and edging, but there are many alternatives in both these fields.

Cutting

Almost all glass will require cutting to the job size requirements, but this process also includes cuts to produce as irregular shapes, such as raked windows, shower screens with cut outs for fittings, glass walls needing spider fittings and custom profiling.

  • Various regular and irregular shapes required are cut with a CNC machine.
  • V Grooved cuts in the face of glass, or brilliant cut, provides an alternate decorative finish.
  • Drilling – Holes from 5mm to 100mm can be drilled into the glass, but the hole diameter must be equal to or greater than the glass thickness. Holes can include a countersunk rim. The hole edging has a ground finish.
  • Shaping – glass can be cut at special shapes or profiles to custom requirements.

There are edge clearances that are relative to the glass thickness for the size and location of cut outs and holes drilled into a sheet of glass. Please contact your manufacturer for exact positioning limitations.

Edging

Edging provides a range of options for the perimeter of the glass to suit its application. Different edges are applied for ease of installation, to assist with further processing or to achieve a look.  One common process is arrissing – a term used to describe the method used to grind the sharp edges of glass to make them safer to handle.

  • Plain cut glass, is called Clean Cut
  • Glass to be toughened requires Rough Arris edge work – arrissed edges with a rough ground finish.
  • Smooth Arris is similar to the rough arris, but with a smoother finish to the edge.
  • Flat Grind or Flat Smooth edges are machined smooth edges suitable for silicone butt jointed applications.
  • Flat Polished is the neatest finish used for exposed edges of glass.
  • Mitred Glass has a 45 degree bevel on one side with an edge finish suitable for mitred silicone butt joints.
  • Round and Polished edge work gives the glass a curved edge for exposed perimeters.

Secondary Manufacture

Secondary Manufacture takes the various types of float glass and changes the properties in a range of production processes.

Heat Treated Glass

A general term used to describe the process of further strengthening or testing glass in a second heating and cooling process. Its is the way or speed in which the glass is cooled gives the glass stronger properties, and length of heating to test the glass.

Heat Strengthened Glass

Heat strengthening is a treatment of glass that induces a high compression layer on the surface.  This is done by cooling the reheated glass at a specific rate. This process makes glass twice as strong as annealed glass, although it is not considered safety glass.

Toughened or Tempered Glass

Toughening glass also induces a high compression layer in a similar process to heat strengthened glass. To toughen the glass, the heated glass is cooled very quickly. This makes it 4 to 5 times stronger than annealed glass of the same thickness. Certain thicknesses are considered A grade safety glass – refer to standard AS 1288.

Heat Soaked Glass

Toughened glass can spontaneously shatter due to small imperfections in glass called Nickel Sulphide inclusions. They are rare, but undetectable, and so, to ensure the glass will retain its form, heat soak testing is done. The glass is heated for a period of time which induces the Nickel Sulphide inclusions to rupture if they are present.  Glass that passes the test, has a markedly reduced possibility of failure once in location.

Curved Glass (toughened)

Curved Glass that requires toughening is bent in the toughening process.  A series of rams fold the glass to the desired shape. Tighter corners and soft curves are achievable.

Off Line Coating

High performance glass has a coating applied to its surface. Different looks can also be achieved with colour and reflectivity. Although large steps in technology over the last couple of years have increased the durability of off line coatings, some are quite delicate, and cannot be heat treated.  Others need to be used in an IGU, so the coated side of the glass is sealed from the elements and physical damage.

Laminated Glass

Laminates are made of two or more pieces of glass permanently bonded together with interlayers. Interlayers are made up of various materials to give the completed glass additional properties, for example, acoustic, colour and UV eliminating. Laminated glass is considered A grade safety glass.

IGUs

IGUs consist of two panels of glass fitted together with a hermetically sealed air space in between to provide an insulative layer protecting against thermal and acoustic issues. The air in the gap is dried to prevent condensation issues.

Other common glass terms

The following terms are not processes done to manufacture glass, but are descriptions of how they are classed, rated and used.

Double Glazing

Double glazing is when two pieces of glass are used with an air gap in between. Special framing suites with glazing pockets front and back are considered double glazed, as are jockey sashes and IGUs.

Monolithic Glass

Monolithic glass is a single pane of glass as opposed to laminated, double glazed or insulated glass units.

Safety Glass

Safety glass is processed glass that is manufactured to satisfy the requirements of AS/NZS 2208 for safety glazing. Laminated and toughened glass are rated Grade A. Wired glass is rated Grade B.

Security Glass

Security Glass is designed to repel violent attack. They are usually combinations of laminated glass that incorporate toughened or polycarbonate combinations. They are not necessarily considered Safety Glass.

Part two to be released in November –

I hope you found these descriptions useful. In part two of this article, thermal glazing terms and properties will be discussed. It will include the terms used to measure and describe performance, what basis the measurements are made from and a comparison of data commonly used – glass only vs whole of window data.

Glazing 918 Darwin Apartments in a Single LEAP

G.James Glass and Aluminium - Transport DivisionStage 2 of the Australian Defence Force’s accommodation upgrade to their Single Living Environment and Accommodation Precinct (LEAP) in Darwin saw the construction of 918 new apartments. It was a highly organised development that had strict protocols and required innovative task management to accomplish the project.

This upgrade will improve and better integrate the living standards and communities where single defence personnel reside. The project is being managed by the Plenary Group, recognised as international specialists in providing whole community concepts, with Woods Bagot as the architect.

G.James Role

G.James Glass and Aluminium’s Darwin office successfully negotiated the contract to supply and fit glazed windows, door frames, security doors and louvres to the various planned concepts in two locations – Larrakeyah (in the city) and Robertson (rural). Each site had individual acoustic, thermal (energy efficiency), wind loading, water penetration and bushfire requirements which formed part of the specification. To ensure compliance, G.James undertook  product modifications, the development of new systems and conducted testing for the intended suites. The contract is to be achieved in two phases of supply and installation that span over 1 ½ years.

G.James is organised to take on projects of this scope. Divisions including business support services and transport are combined with a large workforce and the latest technology to fulfil the resource requirements of larger ventures. For the Darwin project, initial discussions internally located potential branches with facilities and personnel available. Once the project was awarded, managers designated the resources available to meet the commitments.

Design

Darwin comes with stringent water and wind pressure requirements.  Product testing was needed for the new 472 Series door framing system and the 246 Series sliding door for Darwin’s conditions.

Energy efficiency was addressed using IGU’s.  This also helped resolve the acoustics issue at the Robertson location, as there was a flight path located overhead.

BAL Rating

Bushfire ratings are addressed at the Robertson location due to the proximity to bushland in its rural setting.  A Bushfire Attack Level (BAL) rating is given to an area or facade to determine the requirements of the materials used.  Glass and gaskets are selected that comply with these conditions from the G.James BAL Manual.

The BAL ratings applied to G.James materials have been determined from AS3959 as “Deemed to satisfy” or the prescriptive method.  The prerequisite for the physical properties of glazing materials in bushfire prone areas is to resist ember attack and radiant heat transfer.  Your local branch or G.James representative can give you further information on BAL compliant products available.

Implementation

The work was divided up in accordance with the capabilities and current workloads of various branches. Some were accustomed to this volume of work, and others were introduced to it.  The branches involved are outlined as follows, with a brief summary of the who they are, and a quote about what this project entailed for them:

Head Office

Initially, the Business Support Service division at G.James’ Head Office assisted the Darwin branch with project specific engineering, product design, contract administration and material / production coordination.

“This included a review of the products to create efficiencies in product manufacture and installation. Because of the distance that products were to travel by road, we also orchestrated the design of several specific packing crates.” – John Staunton (Manager of Business Support Service).

G.James’ Head Office is charged with the role of being the central point of direction for the branches with regards to technical advice, administrative services and major project logistics & coordination. This responsibility is assisted in the fact that the Head Office is in close proximity to the Group’s major manufacturing facilities at Eagle Farm.

Maroochydore Branch

Maroochydore supplied the entry door frame, highlights and sidelights made with the new 472 Series, as well as Crimsafe screens.

“For 12 months, the Darwin Defence Accomodation has been keeping our commercial and Crimsafe departments with a constant flow of work. The Emmegi CNC machine has been vital part of the processing for the doors required on this project” – Darren Mahoney (Branch Manager)

Bundaberg Branch

Bundaberg worked on 475 Series fixed louvre grill and top hung sliders, Crimsafe screens for the 246 Series sliding doors, and 475 Series hinged Doors.

“It has been amazing to see the various number of branches working together to have all items made, packaged and then transported to Darwin (without damage) ready for installation all within the tight time frames. “ – Damian Perry (Estimator)

KDC

KDC (or the Knock Down Components factory in Brisbane) cut and processed assembly kits for the 246 Series sliding doors.

“We have only had to replace two door frames due to transit damage which demonstrates our attention to detail and ability to supply component parts to the correct specification on time to allow for efficient project management ongoing.” Jason Claridge (Branch Manager)

KDC typically make standard glazing packages for nationwide distribution.

Riverview

Riverview provided framing for the 472 Series fixed glazing and hinged doors.

“Riverview are accustomed to national distribution, being the only manufacturers of double hung windows, so coordinating this project was not out of character.  It did allow us to contribute our other skills and it was fantastic to be a part of such a combined effort.” – Ben Driessen (Branch Manager)

Along with Double Hung Windows, Riverview have a stock of unusual glass types and patterns that are invaluable to replacing period style glass.

Woodridge

Woodridge took care of the 048 Series fixed and awning windows.

“The scale of work for this job saw our manufacturing processes streamlined. It is good to know just how much work we are capable of doing.” – Garry Fulton (Branch Manager)

Woodridge produces almost all products made by G.James products (except double hung), and services the area from south of the Brisbane river to the top of the Gold Coast and out to Manly and Redland bay. They also make a lot of commercial products for Western Australia, and supply 048 series hopper windows to other branches and departments.

Glass Department

The Glass Department in Brisbane manufactured all the glass for the project.

“Our glass department is built to take mass orders of this size, so implementing it was not a problem.  It is good to work on this scale of project, knowing we are contributing to such a large G.James effort.  It is what makes G.James the company we are – we have the ability to take on this kind of work as we have the most sophisticated and modern technology available to us.” – Tony Evans (Operations Manager)

The sizeable glass operations produce many different types of glass – from sizing annealed, coated and tinted, to manufacture of laminated, toughened, printed, patterned as well as IGU’s.

Mechanical and Transport Division

Mechanical and transport departments provided transport for all the components to be brought to Brisbane for coordination and shipping to site.

“We coordinate this type of work all the time – the volume of this job was quite large, however, and meant strict management of delivery – the right products at the right time.” – John Erskine (Transport Manager)

Transport run a fleet of trucks up and down the East Coast of Australia (Sydney to Cairns) to service delivery of the full range of G.James products.

Darwin

Darwin – project coordination and implementation.

” We would never have been able to pull it off without the support of all the other branches that got involved and helped us make this job a reality. To everyone – thanks, it was greatly appreciated.” – Scott Harris (Branch Manager)

On Site

The products, when ready, were transported to Darwin, and fixers were sub contracted to carry out the vast workload at installation.   Attention to detail was essential as all the glass for this project was site fitted because of additional fixings in the glazing pocket required to meet the high local wind loads.

Project status

The project is in its final stages, and is projected to be complete by the end of this year (2013).  Coordinating our resources to achieve higher rates of product supply is not a new service performed by G.James.  We are capable of performing this kind of logisitical coordination to make this scale of projects feasible. G.James welcomes discussion to assess how we can provide solutions for any similar large projects.

Eagle Farm Bus Depot – A G.James All Rounder

G.James, Gossi Park and QuickAlly Access Solutions at the Bus DepotA project showcasing the many products G.James Glass & Aluminium and affiliates produce, is due to open next week. Facets of the G.James organisation, including metal fabrication, Gossi Park & Street Furniture, glass and QuickAlly Access Solutions scaffolding, have made their own way to be part of a humble bus depot.

The Eagle Farm Bus Depot has been recently constructed on Schneider Road in Brisbane. It spreads out over a large area that is mainly car park, or bus park, for the automotive fleet. The industrial surrounds of the location require an outdoor area that is visually protected, yet bright and airy. These qualities were put in place by architects Nettleton Tribe and built by Adco, with landscape work sub contracted out to Penfold Projects.

Setting the scene in an industrial neighbourhood

The brilliant colour of the louvres dominates the skyline, blocking out the surrounding visual hubbub of transport. The powder coat colours chosen, Dulux Duratec Intensity Yellow and Interpon Ultriva Sensation Gloss orange stand out from the background colour, Dulux Zeus Silver Grey. They are randomly alternated, and square and elliptical profiles were used to enhance the arbitrary nature of the feature screens.

The south side of the building uses horizontal louvres. It overlooks the parking spaces for the buses.  The horizontal lines making it easier to see through these to monitor the movements of the buses coming and going, while still allowing the colour and striation to make a visual impact.

The north side of the building has an outdoor seating area that uses vertical louvres as a fence like barrier. They vary in height to follow the incidental theme, making the area less formal and lending more interest.

Quick Solutions

G.James Joinery or Light Metal Fabrication Department won the tender through Adco to coordinate the design, manufacture, production and installation of the louvres.

The on site installation was sub contracted to a company that utilise the QuickAlly aluminium mobile towers scaffolding system. They used this to access the top of the posts and higher louvres (or higher end of the louvres in the vertical areas). It was an ideal situation for the mobile scaffolds, as their height is adjusted simply to meet the level of the work area. They are lightweight and able to be manoeuvred easily along the louvres providing a safe, secure platform to do the installation from.

Creating atmosphere

The finishing touches, to make the place welcoming and user friendly, were provided by Gossi Park & Street Furniture. Gossi’s products were specified by the architect, Nettleton Tribe, and were coordinated through Penfold Projects.

21 settings are scattered in two areas, using Access Tables and Parkway Seats. Access Table are disability compliant, and positioning of the Parkway seating allows enough space for wheelchair use.

The “planks” of the furniture have been powder coated a reddish brown for a timber look – a colour called Headland. The frame and legs are powder coated Shale Grey – a matt metallic look. Using aluminium planks provides a longer lasting, low maintenance product, and the powder coat will allow it to retain its original look. Please note, these products are in shaded areas. Using powder coat in the sun can cause the products to heat up to uncomfortable levels.

There are four BCC waste bin enclosures to house garbage bins provided – two to each area for recycling and general waste. They are ideal for concealing waste, and easy to empty. They are the preferred bin used by the Brisbane City Council for their ease of use and stylish design. The furnishings and landscaping of the area exudes a pleasant vibe for professionals to take time out and congregate.

A glass choice that is no surprise

On site another sub contractor has independently chosen our product for use in the buildings glazing. The overall impact of all the products that have come together under separate circumstances is a delightful find. It is good to know the quality and professionalism of G.James service and products are utilised and appreciated by many, and can come together in jobs such as these for some spectacular results.

New Glazing Product: Low E Coated Glass Launch

Solarplus TLE 62 new glass product

G.James Glass and Aluminium pride ourselves on being at the forefront of the latest product developments and are proud to offer a new range of high performance Low E coated glass products, Solarplus TLE62. This new range of coated glass will be incorporated into G.James TwinGlaze Insulated glass Units and will supersede the current range of Solarplus Low E products offered.

Benefits

Low E glass has a range of distinct benefits – the major function is to provides better thermal performance. The new Solarplus TLE 62 glass produces results in an efficient method, requires shorter lead times for production, and is ideal for jobs large or small.

Solarplus TLE 62 has high visible light transmittance and neutral appearance in both transmittance and reflectance which is low internally and externally.  Please refer to the performance table below for data, and please note, this is for glass only performance. Contact G.James for whole of window data.

Solarplus TLE 62 new glass product

The thermal performance is excellent with low U Values and Solar Heat Gain figures.

Colour Options

The Low E coating is on clear glass and can be combined with tinted glass to provide different aesthetic qualities. The range includes:

  • Grey
  • Green
  • Bronze
  • Blue
  • Super Green

The Solarplus TLE 62 is a durable coating that is able to be heat treated for toughening where it is required.

The G.James manufacturing facilities are currently being upgraded, and this product will be available in October, 2013. Please contact us with any further enquiries about this new product range.

Gasworks – A Modern Development with a Heritage Heart

Gasworks building developmentOngoing development of a historical site located at Newstead (Brisbane), sees it transforming in stages to a new mixed use precinct. The name derives from the sites original use – the gasworks, and part of the project is to protect the heritage listed gasometer located prominently amid the gasworks buildings.

Originally built in 1863, the gasometer once stored gas in a large bladder contained within its frame work.  The Gasometer has been fully restored ensuring the ornate pinnacles and lace work beams stand as equal alongside its newly constructed neighbours.  It creates a unique contrast set amidst the strong lines and bold shapes of the modern architectural features of the Gasworks building development.

Designed by the same team that worked on the adjacent Energex building – Architect Cox Rayner and builders FKP, the buildings in this phase of construction comprise of Building A on Skyring Terrace (five storeys) and Building E on Longland St (three storeys).

G.James Role

G.James Glass and Aluminium supplied and installed glazing facades, doors, windows and some extruded sun hoods. Building A has a proposed 5 star green star rating – so energy efficiency, acoustics and air infiltration were important design factors. As such, products with proven test results were selected for use.

Building A

Building A comprises ground floor shop front retail with four upper levels of offices. The offices utilise the flush glazed 651 series glazed with IGUs made up of green glass with a low E coating for energy efficiency, a 12mm air space, and 6mm clear glass internally. This also assisted in achieving a better acoustic rating.  Spandrel panels were made with a green ceramic painted surface – a premium spandrel glass option  that maintains the look set by the vision area.

Building E

Building E was a combination of two levels of residential apartments along Longland Street, two levels of office space along the breeze way between the buildings, and a retail shop front precinct on the ground level. The offices in building E utilize the 650 series, also flush glazed, but to accommodate 11.52mm laminated glass. The glass has a low E coating and the same colour, but didn’t require the same level of acoustic rating or energy efficiency. The office glazing also incorporated architectural features such as glass fins for extra strength and sun hoods for protection.

The residential apartments use a range of glazing styles. Fixed framing used the 650 series system with 265  series awning windows spaced across the facade. Balconies feature four side supported 550 series balustrades with access through 445 series sliding doors.

Shopfront Design Problem

The retail areas required a centrally glazed pocket, but the opening size and wind loads exceeded the constraints of the current system.  As many architects are looking for options to make windows larger, the decision was made to replace the current aluminium vertical members, the mullions, with a stiffer option. The new design also incorporated the ability to strengthen it further. This new addition to the G.James range is used extensively throughout the Gasworks project.

Practically Completed

Practical completion was achieved on the 3rd August, 2013, however there are still minor works, interior fit outs and landscape work under way.  Building E has been designed so a residential tower can be constructed above it in the future.

The Gasworks project is an aesthetic feast, and well worth a look if you are in the area. Please consult the interactive map project to get the location and a summary of the project information.

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:

Generic and Custom Plastic Extrusions, Gaskets and Seals

PVC extruded plastic gasketThe G.James Glass and Aluminium Plastics department has been operating since 1995, and started out manufacturing just 2 products for in house use. Type and quantity of manufacturing has been growing steadily ever since. Commercial sale of products initiated 5 years ago, and now supports several industries.

G.James Extrusions

The industries that G.James manufactures PVC plastic extrusion for include – building and construction, automotive, commercial refrigeration, marine, shop front, internal fit outs and railways to name a few. They come in a range of colours and PVC types, from rigid, semi rigid and flexible, including nitrile or rubber modified and TPV (Thermo Plastic Vulcanite) or Santoprene equivalent (this has the same properties, characteristics and function, but without the Santoprene brand name) as well as Santoprene, if its specifically required. Co extrusions (extrusions made from two different materials) and bushfire (BAL) rated extruded gaskets are also available.

The G.James facilities are capable of large scale commercial production. The production lines can produce up to approximately 2000m of plastic extrusion an hour – depending on the size and shape of the profile. Products are designed up to 100mm in Circumscribing Circle Diameter (CCD). At peak times, it will use up to 40 ton of material a month – and that’s not at full capacity.

Extrusion design

After initial contact, the design process involves an in depth look at what is required – the use, appropriate material for the conditions – sun and weathering, heat and chemical exposure. Identifying potential issues and mitigating them, or troubleshooting issues that may have occurred previously. Assessing die design and making a more effective proposal are all looked at prior to signing off drawings for a die to be made. Die trials are run and the resulting profile measured up for quality assurance purposes before commercial runs begin.

This process can take up to a couple of months if there is a lot of design involved, but is usually less. Ordering plastic extrusion has a two week lead time, but standard runs or more urgent requests can be processed to cater to customer needs.

Quality

During the design process

Efforts are made to ensure the die design is as beneficial and cost effective to the customer as possible. For example, a recent job started out with a profile design from a customer that required considerably expensive tooling and production costs.  Working with the customer and making a few die modifications, these costs were brought down by 60% . No impact was had on the effectiveness of the extrusion.

As an initial saving, G.James can arrange to have the tooling price amortised into the production price per metre to offset the lump sum.

Use in situ

18 years of experience by the PVC extrusion manager, Jason Clarke, ensures personal service from someone who knows how to make it work. Trouble shooting feeding problems, stopping gaskets from “popping” out of position, gasket “wave” problems and better shape design are among other issues that are addressed.

Point of manufacture

A length from every roll of extruded plastic is tested to ensure a quality product. Measurements are taken and information is recorded and stored so it can be tracked back to when and how it was made. Materials that work into other G.James products are also trialled for a suitable fit on completion to ensure a whole of system customer service.

Back end quality control

G.James conduct investigations into existing scenarios that are having problems. Extrusion and glass checks, incorrect use and out dated design issues can be looked at to assess the cause of any issues. Advice is given on the findings, whether it is a change in plastics die design, or other members that are found to be out of tolerance.

Manufacturing Process

It’s a short but interesting manufacturing process. The material comes in pellet form that is control fed through a hopper into a spiralling screw or ram. The pellets are heated, mixed and compressed as they are fed through the spiralling screw, and finally forced through the die into its final shape. After the gasket is extruded, it is immediately cooled in chilled water, and then dried before being cut into designated lengths and boxed, or rolled onto a spool.

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Recycling

All off cuts of plastic extrusion are recycled on site. They are shredded and prepared to go through the same hopper feed and production process. As a quality control issue, recycled material is only used on non-structural gaskets, such as fly screen splines.

Brisbane designed and made, supply is distributed Australia wide, with much of our standard range available off the shelf at any G.James branch. For more information on product and supply, call the PVC manager, Jason Clarke, on 0403 352 703 or 07 3815 4908. Keep up to date by looking up the PVC page on the G.James website.

Thermal stress glass breakage

AGGAThe following fact sheet has been prepared by the Australian Glass and Glazing Association Technical Sub Committee and has been reproduced with the kind permission of the AGGA.

The original technical fact sheet is available as a downloadable PDF file.

Thermal Broken Glass

Introduction

Thermal stress occurs in glass when there is a temperature variance in different parts of the glass. If the stress caused by the temperature difference is greater than the strength of the glass, thermal stress glass breakage will result.
Thermal stress glass breakage is not a new phenomenon and it has been relatively well understood in commercial glazing for many years. However, given the increasing use of high performance, energy efficient glazing and the fact that some of these products can carry a greater risk of thermal stress, it is important that everyone involved in the glazing industry has a better understanding of thermal stress, its cause and how to prevent it.
As thermal stress breakage is not often due to a glass fault, but rather the result of a set of conditions that a pane of glass is exposed to, it is generally not covered by a glass supplier’s warranty.

Identifying thermal stress glass breakage

A glass fracture can be identified as a thermal stress breakage if the start of the crack is at 900 to both the edge of the glass AND the face of the glass. Depending on the magnitude of the stresses involved, the crack may only travel for a few millimetres before branching out or veering off-line, so the 90° angle of the initial fracture may not always be immediately apparent.
Breakages caused by thermal stress can be characterised as either low stress breakages or high stress breakages. Low stress breakage is characterised by a single crack that “lazily” makes its way across the glass, while high stress breakage is identifiable by the initial crack branching off into a number of separate fissures a short distance from its origin.

What causes thermal stress?

As mentioned previously, thermal stress is caused by varying temperatures in different parts of a glass pane. Absorption of the sun’s energy is one of the main causes of this temperature difference. The section of glass exposed to the sun absorbs the sun’s energy and, as a result, heats up. Any part of the glass which is shaded from the sun, for example, by the window frame, stays relatively cool.
The hot glass expands while the smaller, cooler area doesn’t. If the cool area of the glass isn’t strong enough to withstand the forces imposed by the expanding hot section of the glass, thermal stress breakage will occur. Putting the forces required to induce thermal stress into perspective, Pilkington estimate that for every degree in temperature difference between the edge of the glass and the centre of the glass, around 0.62 MPa of stress is introduced into the glass. Given that in some cases temperature differences of 20 to 30°C can occur, that equates to around 12 to 19 MPa. This is higher than the design stress used for wind loading!

Thermal stress risk factors

Given that thermal stress is caused by differences in temperature in a piece of glass and that breakage occurs when the ability of the glass to withstand this stress is exceeded, any situation or factor that increases this temperature difference, or decreases the glass’s strength, increases the risk of the thermal stress breakage.
Factors that can affect the risk of thermal stress include:

Edge Condition

Damage to glass edges during manufacture or installation is arguably the largest cause of low stress thermal breakage.
As US glass manufacturer PPG puts it: “The as-cut quality of glass edges is the single most important factor affecting the edge strength of glass. Poor cut-edges quality can reduce the glass strength by 50% or more…” “Glass edge quality and the resulting glass edge strength is particularly critical to the performance of the glass under the thermal loading …” Glass Edge FeatherThe level of thermal stress that a piece of glass can withstand is directly affected by the condition of the glass edges. The edges that are most resistant to thermal stress breakage are good quality clean-cut edges with no shells, vents or shark teeth. This may be difficult to achieve in laminated glass and edgework may be required to smooth the edges.

Glass Type

Different glass products have a different tolerance to thermal stress. Generally, the more solar energy a glass product absorbs, the higher the risk of thermal stress breakage. All glass manufacturers provide data on the solar energy absorption properties for their products.
Solar absorption can vary greatly, even between similar products. The use of a reflective coating can significantly increase the amount of solar absorption. This is because, in effect, the glass is absorbing the solar energy both on the way into the glass and then again on the way out after it hits the reflective coating.

Example:

Uncoated 6mm grey glass has a solar absorption rate of around 45%, while the addition of a reflective coating to this product increases solar absorption to 63%.
The use of transparent Low E coatings can also increase the solar absorption rate of glass. Low E coatings are designed to reduce the passage of radiant heat flow through the glass to improve energy efficiency. This leads to higher glass temperatures and increases the risk of thermal stress.
Another significant risk factor is the addition of heat absorbing films or any partial covering of a glass pane by other products (such as signs or paint) after installation. Both of these can increase the risk of thermal stress.

Glass Size

The larger a pane of glass, the greater the area of glass that is absorbing the sun’s energy, compared to its relatively narrow cooler edges. The larger area of hot glass results in higher levels of thermal stress in the edges of the glass.

Exterior Shading

Whilst glass properties are well documented and can be taken into account during the design phase of a project, accounting for exterior shading can be more problematic.
The effect that an external shading device has on thermal stress depends on a combination of its size, shape and location on the glass. Exterior shading is further complicated by its seasonal nature; as the sun’s position changes throughout the year so too does the shadows it casts.
In general:

  • Shading that covers 50% or less of the glass is more unfavourable than a device that shades a greater percentage of the glass;
  • Static shading is more unfavourable than mobile shading;
  • V or L shaped shading induces higher thermal stress, particularly if the point of the V falls on an edge of the glass.

Interior Shading

A thermal stress risk factor that is encountered more often in residential construction than commercial, is the use of curtains and blinds on the inside of a window. The impact that blinds and curtains have on thermal stress depends on the colour, type and other factors, however the effect can be significant.
While close fitting blinds or curtains help to minimise heat transmission into or out of the building, they can significantly add to the risk of thermal stress. To minimise this, the space between the glass and shade must be at least 50mm (preferably 150mm) and should be vented. Ventilation is provided by leaving a gap between the blinds and the walls, or frame, of 50mm at the head and 25mm at the sill.
The effect that blinds and curtains have on thermal stress is also dependent upon how much energy they reflect back onto the glass. Light colours are good reflectors while dark colours are not. Closed weave fabric helps trap heat more effectively while open weave lets the heat pass through. Venetian blinds are excellent heat reflectors as are metallised blinds.

Heating & Cooling

Artificial heating and/or cooling devices should be positioned so that they do not blow hot or cool air directly onto the glass surface, nor into the space between the glass and the curtains. Doing so may result in varying temperatures on the glass surface and therefore increase the risk of thermal stress.

Glazing Method

Commonly used glazing methods do not significantly affect the risk of thermal stress. The exception to this is structural glazing, which reduces the levels of thermal stress by reducing the temperature difference between the glazed edge and the centre of the glass. Care should be taken when using any glazing method that either encourages the transfer of heat away from the glass or covers unusually large amounts of the edges of the glass.

Managing the risk of thermal stress

The risk of thermal stress breakage can be eliminated by managing the factors outlined above or by heat strengthening the glass.
Heat strengthening increases the strength of the glass, which allows it to resist the thermally induced stress. Heat strengthening can be relatively expensive, particularly if required for laminated glass, so unless replacing glass, which has been broken under thermal, stress, a method of quantifying the risk level is needed.
Many glass manufacturers’ websites provide detailed information on thermal stress breakage. Some also provide online tools that enable you to perform a thermal stress analysis yourself, or they will perform a thermal stress analysis for you providing you purchase glass from them.
By using available information, the glass installer can objectively assess the risks prior to installation. In some cases redesign may be possible, eliminating the need for heat strengthening and therefore saving unnecessary expense.

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…