FAQs » Viridian Glass


We haven’t got the answers to all of life’s questions, but when it comes to glass, our FAQs probably have it covered. Search for the answers below.


What is Rw?

Rw is the ‘weighted sound reduction index.’ It is a number used to rate the effectiveness of the glass as a noise insulator and is measured in decibels (dB). It also takes into consideration a correction factor for the response of the human ear. For example, if a busy street has a noise level of 75dB and the required level of noise in a room is 40dB, the Rw value of the required glass is 35dB. Glass types with a Rw value greater than 35dB can then be offered as solutions.

It is worth remembering that every 10dB reduction is perceived by the ear as being half as loud, so that a 20dB noise reduction would reduce the perceived noise by 75%.

Why does the noise from a car sound different from the noise from aircraft?

This is because the noise from the traffic is at a different frequency than that of the aircraft and the ear picks it up as sounding distinctly different.

What is so different about VLam™ Hush over standard float and laminated glass?

VLam™ Hush uses a specially developed interlayer which further enhances the noise insulation properties of the glass. It reduces the coincidence dip even further than both float glass and standard laminated glass which means that the sound insulation properties found in much thicker glasses of each type can be achieved in a product that is both thinner and lighter. For example

Will just choosing glass designed to reduce my noise levels solve my noise problem?

It will most likely help however there are some potential pitfalls. A number of other considerations also have to be carefully assessed, including;

– Vents in the wall providing a simple entry point for noise.

– The gap between the roof and the ceiling above the external  walls which allows noise into the ceiling space.

It’s common also, especially in domestic applications, for the windows and doors not to be sealed adequately to the building frame allowing noise to easily penetrate. Gaps and air leakage through existing window frames will permit significant noise penetration. All these issues need to be addressed if you are going to achieve maximum value out of the noise reduction properties of the glass.

Is double glazing an answer to a noise problem?

Not as much as you might think. Standard double glazing has quite a small air gap between the two glasses which limits the effectiveness. The maximum gap for a sealed double glazed unit is about 22mm which will make some difference. However, the use of an air gap of 50mm to 200mm will make a substantial difference. This cannot be achieved with standard sealed double glazing. It would require two window frames set one behind the other to create the gap. VLam Hush™ used in either one pane or both is ideal where you need noise protection along with thermal comfort.

Does the width of the air gap in a double glazed unit make any difference?

Only a little, until you reach very wide air gaps; usually a minimum of 50mm. This is because it is only at these wider air spaces that there is enough air within the gap

To sufficiently dampen the effect of the noise. The use of different gases in the air space, i.e. argon, has no effect on the sound insulation properties of the double glazed unit.


What is a ‘coincidence dip’?

A coincidence dip is when the glass vibrates or resonates at the same frequency as the source of the noise. Essentially it is a frequency range in which glass has a greater transparency to sound waves.

With float glass, the point at which the coincidence dip occurs varies slightly with its thickness, but generally occurs with high frequencies such as those associated with aircraft noise. It should only be used therefore where lower frequency noises, such as those associated with traffic, need to be reduced.

With laminated glass, the PVB interlayer allows greater sound reduction by reducing the coincidence dip making it better at reducing higher frequency noise such as that associated with voices and aircraft.

Standard double glazed units do not provide good noise control, requiring very wide air spaces, of up to 200mm, to be effective. A solution is using different thickness glasses as the two panes of the unit, 2 panes of laminated glass or a combination of both depending on the level of noise reduction required.

How are the sound reduction properties of the glass measured?

A sample of glass is glazed in an acoustic test chamber where it is subjected to various frequencies. Sensitive microphones compare the source side with the receiving side to produce a plot and measurement of the effect of the glass at each frequency. The chamber is calibrated to ensure that it is the glass performance only that is being measured. In the field, anyone with a noise meter can potentially measure noise. However, it is a specialist’s field of work, and should be undertaken by noise consultants who have the knowledge to do a noise survey and present the information in a proper and useful way. Inexperienced use of a meter will not produce information that can be relied upon.

Does distance affect noise levels?

Yes, noise decays with distance. The surrounding buildings can influence the noise level and road traffic noise can be a nuisance in tall buildings due to channeling effects and the incidence of the sound to the facade.

How quiet should my room be?

This depends on the use of the room. It is largely a subjective judgment by the occupiers on what level of noise they are comfortable with and will vary by location. For example, people generally only feel comfortable with a noise level of 30 – 40dB in a bedroom but will happily work in an open plan office with a noise level of 45 – 50dB. You would expect a background noise in a library to be around 30dB.

If you make a room too quiet, then you begin to listen for other noise sources that you would not have picked up before. Go for a noise level appropriate to the use of the room.

What is the difference between dB and dBA?

The dB scale is used to measure sound level. However, because the human ear does not respond equally to all frequencies, we often use dBA as a scale of measurement. This is an adjusted measurement of noise that takes into account the sensitivity of the human ear to the various sound frequencies which we can hear. Certain frequencies irritate more than others. As an example, think of fingernails dragging across a blackboard.


What are the major benefits of Viridian DecorMirror™ over standard mirrored glass?

Viridian DecorMirror™ is specially formulated to provide maximum protection of the highly reflective silver coating without the need for using Copper which is used in the older mirror processes associated with mirror manufacture. This helps in minimising ‘edge creep,’ ‘black spots,’ ‘black edges’ which are often found in conventional mirrors.

The dual coating of the special backing paint applied to Viridian DecorMirror™ also helps protect the coating in bathroom applications where moisture has traditionally affected the edges of conventionally manufactured mirrors. Because Viridian DecorMirror™ does not use copper in its manufacture, it is a more environmentally friendly.

Can I use Viridian DecorMirror™ as a safety glass?

Yes, providing that you specify Viridian DecorMirror™ Safe. This is a mirror with a special vinyl safety backing which enables a Grade A Safety rating to AS 2208 to be achieved.

How do I install Viridian DecorMirror™?

DecorMirror™ can be fixed by frame or directly onto a door or wall. If fixing directly onto a surface,
it is important that the adhesive is compatible with the paint or vinyl backing of the mirror. This is best checked with the adhesive manufacturer. Once identified, it is recommended that double sided tape is applied onto the rear surface of the mirror and the adhesive is applied vertically in between the tape. The adhesive must be neutral cure and not acid cure.

What are your cleaning recommendations for Viridian DecorMirror™?

Viridian DecorMirror™ has increased resistance to a number of cleaners and adhesives, although some cleaning solutions (specifically ones containing acid or ones which are strongly alkaline) can damage the mirror coating.

A recommended method is to apply methylated spirit sparingly onto a damp cloth. Use a lint free cloth to polish the surface dry. Be careful to ensure no abrasives are present on the cloth and ensure no contact is made with the silver backing. Specific care should be taken to avoid excessive cleaning of the edge of the glass, and that moisture is kept away from the painted surface of the mirror.

Do you offer a warranty for Viridian DecorMirror™?

There is a standard 2 year warranty on the Viridian DecorMirror™ range of products. Details can be found here

What glass products do Viridian supply for use in decorative applications?

We have a range of glass products which, dependent on the application, can be used for decorative purposes in both safety and non-safety rated applications.

The range includes:

DecorPattern™ glass – range of different designs for use in windows, doors, partitions, wall panels, lead lights, balustrades, louvres, furniture

DecorMirror™ – An environmentally friendly, copper free mirror with high light reflection for use in bathrooms and standard framed mirror applications.

DecorMirror™ Safe – A special vinyl backed, Grade A safety version of the standard Opt mirror product for use in wardrobes, doors and high activity areas.

Seraphic™ – A range of 16 decorative toughened painted panels used for curtain wall spandrel applications, plus wall cladding and splash backs

Seraphic™ Design – A range of different designs than found in the ‘standard range’ providing different light transmissions and levels of solar control for use in, for example, laminated overhead glazing.

PixaGraphic™ – A custom high resolution digital printed that allows any special design and/or colour to be used for specific project applications.

Browse the entire decorative range of products here

Is Viridian DecorPattern™ glass completely obscure?

The DecorPattern™ glass range offers different levels of obscurity dependent on what product is chosen. No one product within the range is completely obscure, rather providing levels of privacy whilst being able also to offer excellent levels of light translucency. The levels of obscurity offered are ‘Most’, ‘Medium’ and ‘Least’

What is the difference between Seraphic™ and Seraphic™ Design?

Viridian Seraphic™ is a range of 16 standard opaque colours

Can mirrored glass be used as a splashback?

Overall it is not a product which we would recommend as a suitable product for a splash back application. Current Australian standards determine that 6mm toughened safety glass must be used in kitchen splashbacks only. See our ColourBack product range for toughenable painted options. 

Can Viridian DecorPattern glass be laminated or toughened?

Yes, DecorPattern™ glass can be both toughened and laminated to meet Class A of AS 2208. However

Which way should I glaze the textured side of DecorPattern glass?

The glass should be glazed with the pattern to the room side.

Which product can I use for a frosted shower screen?

We would suggest toughened Viridian DecorSatin™ glass with the acid etched side installed to the non-water side.

Will Viridian DecorSatin be as easily marked by fingerprints as sandblasted glass is?

No. The subtle satin like appearance of DecorSatin™ is much smoother than the rough, abraded surface associated with sandblasted glass and as such does not allow dirt, grease and oils to ‘get under the surface’ of the glass as easily. Its surface is also much more durable than that of a standard sandblasted glass product. Refer to DecorSatin™ cleaning instructions for any day-to-day marks which may appear on this glass. 

Can you print custom patterns or pictures on glass?


What are the benefits of Low E glass?

It allows better thermal insulation to be achieved without the need to change the window framing system of an existing house as this would normally have to be undertaken if double glazed units were specified because they are often too thick to fit in normal framing.

It’s the Low E coating on the inside of the building that will reduce heat loss in winter and re-radiation to the inside in summer. This allows a very cost effective balance of performance to be achieved in a relatively thin glass.

When it’s a laminate, it achieves a Grade A safety rating and can be used in low level glazing and in other areas where safety glass is required.

What glazing would you recommend for my house so I can keep it cool in summer and warm in winter?

There are a range of options available dependent on whether a single glazed (monolithic) or double glazed solution is required. That in turn may depend on the framing system desired, the performance criteria required and/or the budget that is in place.

Essentially the performance criteria revolve around blending the solar control and thermal insulation properties of the glass to reduce the amount of heat coming through the glass in Summer and reducing the amount of heat lost to the outside in Winter.

Single glazed options available from Viridian include ComfortPlus™ SmartGlass™ EVantage™ EnergyTech™ & SolTech™

Each product offers different options which can match the customer requirements in terms of solar control, light transmission, reflectivity, thermal efficiency, safety and colour.

Double glazed options permit a wider range of products to be considered across the range and generates the potential for higher performance levels to be achieved; i.e. lower U values in conjunction with greater levels of solar control and higher levels of light transmission.

What does Low E mean and what benefits does it provide?

Low E means ‘low emissivity.’ The main difference between a Low E glass and an ordinary glass is that Low E glass has a very thin coating applied to one side of the glass. This enables the transport of heat through the glass to be reduced. EnergyTech™ and ComfortPlus™ are all examples of a Low E glass. The main benefits of using such a glass are that more warmth is kept within the room, more space can be used within the room as cold downdraughts are minimised, more window area can be used, heating costs are reduced and the contribution the products make in reducing greenhouse emissions.

I have noticed some marks on my Low E glass. Has the glass been damaged?

The Low E coating is actually harder than the glass and consequently is quite difficult to scratch. This does not mean it cannot be scratched, as anything can be scratched if you try hard enough. However, the marks you notice might be abrasion marks. The consequence of the coating being very hard is that it can abrade other materials? So, materials rubbed across the coating can abrade and leave deposits on the surface. For example, if you rub a coin across the coating, a mark will result. The mark is caused by metal from the coin being deposited on the coating. These abrasion marks can be cleaned off and advice on how to do this can be found in the cleaning advice for Low E glass which can be found on our website.

What is the difference between U Value and Solar Heat Gain Coefficient?

U value is the measure of the insulating capacity of the glass. This represents how quickly heat from hot air (not direct sunlight) will pass through the glass. The lower the U value the better the insulation. Glass with low U values are generally used to keep the warmth in the room, in cold climates or at night.

For example, 4mm clear float glass has a U value of 5.9, whilst ComfortPlus™ has a U value of 3.6. So ComfortPlus™ is a better insulating product than 3mm clear float glass.

Solar Heat Gain Co-efficient (SHGC) is the amount of heat from direct sunlight that passes through the glass. This includes sunlight which passes directly through the glass to the room and the amount of sunlight which is absorbed by the glass and later reradiated to the room. The lower the SHGC, the better it will achieve this. Glass with a low SHGC is best used in areas of direct sunlight, for example to reduce the amount of heat coming through the windows in summer.

For example, our 4mm clear float glass has an SHGC of 0.85, whilst ComfortPlus™ has an SHGC between 0.57 and 0.60 depending on the colour. 

What are the advantages of glazing with a toned glass?

It reduces some of the direct heat from the sun passing to the inside of the building. The amount will depend on both the colour of the glass and its thickness. Toned glass is available in a range of colours to enable different aesthetics and performance of the building to be achieved.

Toned glass can be easily incorporated into a double glazed unit if required and can assist in reducing glare, it can be laminated or toughened if required.

Toned glass provides a degree of privacy (depending on colour). However unless incorporated with a Low E coating or used in a double glazed unit it remains poor in its insulation benefits. Clear glass and SuperGrey™ glass have the same insulative benefits, which are the worst in terms of insulation performance

What is ‘R value’ and how does it relate to our performance data?

R value is a measure of how well a material resists heat transfer whereas U value is a measure of how well a material transmits heat. As such, solid materials such as bricks, insulation and walls are measured in R-values whilst glass is measured in U values. Unlike glass where lower U values mean better insulation, for materials that are measured in R values it is the higher the R value the better the insulation. Conversion between the two can be achieved using the following relationship U value =1/R.

What is the difference between hard coated and soft-coated low E glass?

It is a difference between both the type of material used for the coating and the way the coating is applied to the glass.

However, there are several further differences:

Soft coated Low E glasses must be incorporated into a double glazed unit as the coating is ‘less durable’ than a hard coated (pyrolytic) coating when exposed to the atmosphere. Soft coated Low E glasses cannot be glazed in single glazed applications but hard coated products such as ComfortPlus™ and EnergyTech™ can.

Pyrolytic coatings have a long shelf life, whereas soft coated Low E glasses do have a shelf life and will begin to break down if stored for too long without being incorporated into double glazed units.

Soft coat Low E glasses such as Viridian LightBridge™ or PerformaTech™ have significantly lower U values than hard coated pyrolytic glass types.

Hard-coated Low E glasses are manufactured online during the float manufacturing process where soft coats are applied by a special offline process at some time after the glass has been manufactured.

What is the effect of condensation on the coating of a single glazed Low E glass?

If condensation forms on the coated surface of a single glazed Low E glass, e.g. ComfortPlus™,  the glass loses its low emissivity performance characteristics and behaves like normal float glass. In other words, it provides no additional benefits in terms of reducing heat loss from the building whilst the condensation is present. If there is a chance of condensation forming on the inside of the window on the coated glass surface (i.e. in very cold climates), then the best solution is to use a double glazed unit incorporating a low emissivity glass. This further reduces the U value of the glass, keeps the inner face of the double glazed unit warmer and therefore minimises the chances of condensation forming.

How does single glazed Low E glass provide insulation?

The fact that there is a Low E coating on one surface of the glass, glazed to the inside, means that the glass will have a lower U value and hence provide better levels of insulation than normal clear glass. This is because the coating reflects the heat back into the room whereas glass without a Low E coating would allow the heat from the room to pass through it. A good example of this is 6.38mm ComfortPlus™ which has a U value of 3.6 compared to a 6mm clear float glass which has a U value of 5.8, an improvement of over 39%.

Where should a Low E coating be positioned in my double glazed unit?

A low emissivity glass can specifically enhance the thermal insulation of double glazed units. It achieves this by being positioned in the insulating unit with the coating on the glass surface facing the cavity.

In a double glazed unit, counting the surfaces from the exterior of the building, the coating should be on surface 2 (the inner surface of the outer pane) or surface 3 (the cavity surface of the inner pane).

Low E coatings perform the function of enhancing the thermal insulation (reducing the U value) equally well whether it is positioned on surface 2 or surface 3.

General advice is that the preferred location of the coating is on surface 2 of the unit, but if the glass types used in the unit make it difficult to assemble the unit than surface 3 can be selected.

There is no loss of insulation performance by using it on surface 3 however SHGC performances will vary.

When Viridian LightBridge™ is used the coating is installed on surface 3 of the double glazing unit.

Why is the window U value different to that of the glass?

The U value for a window is the combination of the U value of the glass and the U value of the frame. The frame is made of a different material to the glass so will have a different U value to the glass. The overall U values of window system using aluminium, timber or PVC frames for example will all be different even if the same glass is used in each case. Because aluminium frames have a higher U value than those of either timber or PVC, the overall U value of an aluminium system is higher and as such is less effective as a thermal insulator.

Why and where would you use ComfortPlus™ Clear instead of ComfortPlus™ Neutral?

ComfortPlus™ Clear can be used where passive solar design principles are used because it has a higher solar heat gain coefficient (SHGC) than ComfortPlus™ Neutral. Consequently, it has a higher solar heat gain, so it allows more energy through, making it suitable for north facing buildings during the winter months where it can gain from free heat (energy). ComfortPlus Clear has the same colour reflectance as ordinary clear glass where Neutral has a blueish grey appearance.

What is the main function of solar control glass?

Its main function is to reduce the level of solar radiation entering a building. Toned glasses achieve this by absorbing a percentage of the solar radiation within the body of the glass itself whilst coated glasses achieve this by both reflecting and absorbing the solar radiation.

Which is the best type of solar control glass to reduce glare?

A very cost effective way of reducing glare is by the use of toned glass. The inherent nature of toned glass means that glare is reduced due to the toning through the body of the glass. The amount of light transmittance is reduced to different degrees dependent on the colour of toned glass as will be the amount of glare.

For example,

VFloat™ Grey will reduce glare more effectively than Viridian VFloat™ Green because its level of light transmittance is lower.

SuperTones product, VFloat SuperGrey™, is very effective at minimising glare with only 9% light transmittance.

Coated glasses, for example EVantage™, offer much higher levels of solar and glare control due to the application of specialty coatings especially when applied to toned glass.

Is toned glass more susceptible to thermal fracture?

Thermal breakage refers to the cracking of annealed glass cracking due to the build-up of excessive thermal stress developed because of a differential in temperature across the glass. As there is more risk associated with glasses which absorb more solar heat within the body of the glass, there is increased risk of a solar control glass being more susceptible to thermal fracture. We would always recommend that a thermal safety check be undertaken when a solar control glass is being specified to determine whether the glazing is at risk from thermal fracture. An effective way to eliminate breakage by thermal fracture is to heat strengthen or toughen the glass.

Why do different colours of toned solar control glass have different solar control properties?

The different colours across the solar control range absorb solar heat to different degrees and is mainly a function of the amount of colourant that is present within the glass mix when each of the products is manufactured. The role of a solar control glass is to control the amount of solar infrared (heat) transmitted through the glass. Whilst this is controlled via reflectance as well as absorption, the amount of heat absorbed by the glass will be determined by the amount and properties of the colourant within the glass.

Can I mix different thicknesses of toned solar control glass on the same job?

Colour density increases with glass thickness, so the colour of toned glass becomes more intense as the thickness increases. As a consequence, the use of the same thickness of toned glass is required to keep the colour of a building the same. The use of a toned laminated glass will delivery colour consistency across various glass thicknesses.

Do solar control glasses eliminate Ultra violet light from the sun?

Solar control glasses do reduce Ultra Violet (UV) rays from the sun to different degrees. However, apart from Viridian VFloat SuperGrey™ which reduces UV transmission by 99%, the best way to eliminate UV transfer through the glazing is to incorporate a laminated glass in the glazing. All laminated glass eliminates more than 99% of UV, even in its clear form.

What are the main differences between super toned glasses and standard toned glasses?

The key differences are that Viridian SuperToned glasses provide significant improvements in solar control performance whilst providing excellent daylight transmission performance. Viridian VFloat SuperGrey™ provides exceptional solar control properties (with a SHGC of .35) without the need for a solar control coating however one drawback is its low light transmittance of 8%.

The coating on my Low E glass appears to scratch very easily. Why is that?

The coating is actually very difficult to scratch and is harder than the glass. For example, if you scratch the coating with a coin, it is the metal from the coin you see deposited on the glass surface itself rather than a scratch. For that reason, it is advised that metal objects are kept away from the glass surface as much as possible and certainly no metal objects, especially sharp metal objects such as razor blades, should be used to clean ‘stubborn marks’ on the glass. Instructions on the cleaning can be found here

What effect does gas filling a double-glazed unit have on its performance?

Filling with Argon gas instead of air will improve the insulating capacity of the double glazed unit. This is reflected by a lower U value than would result from the use of air. The magnitude of the benefit varies with the size of the gap between the glasses in the IGU. The use of Argon in a 12mm gap will result in an improvement of approximately 6%. Viridian only supply Argon gas as a standard across our complete double glazed range.


Who should I speak to at Viridian?

Well, it really depends what you need from us!

If you are an architect, builder or specifier and you need technical advice please contact 1800 847 434.

If you are a member of the trade who has sales, trade specific or order related enquiries please contact 1800 847 434. 

Alternatively, head to our Branches page and you can find your local Viridian contact. 

Homeowners or renovators – Viridian Glass is a trade supplier only. For all residential glass needs we suggest contacting a relevant glass fabricator or installer in your area directly. Remember to ask for Viridian Glass!

Which product is best for me?

Let’s face it. We’ve got a lot of products to pick from, and even more we don’t have listed on our website. So we understand that it can be hard to figure out which is best for you. But glass plays a bigger role in your building than you’d think, so it really is important you pick the right product.

Luckily, we’ve got our Houses

Which type of glass is best suited to where I live?

To answer this question, we need to know a few things about your home.  Understanding what the climate is where you live as well as what direction your windows are facing allows us to give you the best advice for picking the right glass.

By choosing the right glass you can use the orientation of your house to your advantage. In addition to the position of your house, the position and shading of your windows is also an important consideration. In general, high insulation performance is a good option, while the level of solar control you’ll need depends on climate. Cooler climates favour products which allow in more heat, while warmer climates in the north of the country benefit from glass that keeps warmth out.

For more on choosing the right glass for your climate and house orientation check out our Energy Performance page where we get into the detail.

If you are an architect

What is the next step if I want to get a quote?

To give you the best price indication, we’ll need to know a little bit about who you are, where you are and what you need.

Luckily, we’ve got a team of experts who would love to talk about your project, or put you in touch with the best person to speak to for a quote. 

If you are a member of the trade who has sales, trade specific or order related enquiries please contact 1800 847 434 or head to our branches page and you can find your local Viridian contact.

Homeowners or renovators – Viridian Glass is a trade supplier only. For all residential glass needs and quoting you will need to contact a relevant glass fabricator or installer in your area directly for your project. Remember to ask for Viridian Glass!

I need some help with the glass specification for my project.

You’ve come to the right place. We offer glass products that can greatly improve energy management, comfort, safety, security, colour and design. We’re keen to help you meet specific requirements including acoustic properties, building compliance (including Section J) and engineering support. Whether you’re building balustrades, roof glazing or flooring we can help you.

Please head to our dedicated Specifiers page and complete the online form with as much project detail as possible

How should I clean my glass?

Always use a mild detergent that is specifically designed for use with glass and steer clear of any products that will introduce grit as this can cause scratches.

Also avoid any cleaners which contain Hydrofluoric or Phosphoric acid as they are corrosive to glass surfaces. If cleaning a mirror simply wipe the surface with a few drops of methylated spirits using a damp cloth. Always avoid contact with the silver backing, particularly at the edge of the glass as this can cause damage.

For a spotless surface finish by polishing your glass or mirror using a dry lint free cloth – voila, picture perfect!

If you’d like more information on how to clean glass including specialised instructions for our range of products check out our collection of cleaning instructions