Frequently Asked Questions
ClimaGuard Low-E coating is applied by a process known as magnetron sputtering, which applies several thin coatings of various metal compounds to one surface. Guardian sputter coated low-E glass is available in toughenable versions. There are other types of coated low-E glass and they can be visually different in appearance.
Many buildings in Europe are glazed with the low-E coating on surface #3 in order to reflect the heat back into the building as efficiently as possible. Reducing solar heat gain is most important in commercial buildings where air conditioning costs can be high. Low-E on surface #2 reduces the solar heat gain buy the glazing may appear visually different in reflection when viewed from outside. Low-E coating is often on surface #3 when body tinted or solar control coatings are used on surface #2.
Heat strengthened and toughened glasses are manufactured during a similar process on the same type of machinery. The only difference during manufacture is the application of different levels of stress induced into the product. As a consequence of this, toughened glass breaks into small relatively harmless pieces when broken and as such is considered to be a safety glazing material. Heat strengthened breaks in larger pieces similar to annealed glass and is not considered a safety glazing material unless it is made into a laminated product.
Heat strengthened glass may be installed in any situation that does not require a safety glass. Both glass types are resistant to thermal breakage as they are stronger than annealed glass. However, unlike annealed glass, neither can be cut or drilled after being manufactured and any alterations such as edge grinding, sand blasting or acid etching will weaken the glass and can cause premature failure.
The specification of glass can be a complex and lengthy process. It begins with the external aesthetics, light transmission and energy performance in combination with local Building Regulations, which are developed as the design team and architect define the requirements from the glazing.
Guardian has developed a Product Performance Comparison Tool to assist in comparing existing projects supplied with SunGuard Advanced Architectural Glass products. Please contact your local representatives for further advice and information.
The u-value is a measure of the heat flow through the glazing measure in Wm-2K-1. The lower the u-value the lower the heat loss to the outside of the building and the greater the energy costs are reduced. The performance data provided by Guardian are for the glass performance only, often referred to as the centre pane u-value, which does not take account of any heat loss through the perimeter of an insulating glass unit or frame.
The solar factor (total transmittance) of a glass configuration is relative to that of 3mm clear float glass (0.87) and is used as a performance comparison. The lower the shading coefficient number, the lower the amount of solar heat transmitted. The short wave shading coefficient is the direct transmittance (T) of the glass as a factor of the solar factor or total transmittance (g or TT) of 3mm clear float glass (T ¸ 0.87). The long wave-shading coefficient is the internally re-radiated energy that the glass has absorbed as glass. It is determined by subtracting the direct transmittance from the solar factor (total transmittance) of the subject glass and then dividing by the solar factor ( total transmittance) of 3mm clear float glass (g-T ¸ 0.87).
The use of air or argon is usually defined by the u-value requirement for the insulated glass units for each specific project. In Southern Europe it may be sufficient to use air filled units whereas in Northern and Central Europe, in order to minimise heat loss during the cold winter period it is often essential to incorporate argon within the cavity. Local Regulations often dictate the level of insulation required.
You can easily obtain SunGuard samples measuring approximately 290mm x 210mm for your project from your local office or though our sample request form in this website.
The SunGuard Advanced Architectural glass products offer the largest range of toughenable sputter coated glass products. The products can be processed by one of our SunGuard Processors, local to your project, ensuring minimal lead times on new and replacement glass.
All the independent SunGuard Processors are approved and certified by Guardian in accordance with the procedures and practices for the processing of Advanced Architectural Glass. Contact your local SunGuard Processor for specific product availability and lead times.
11. Does Guardian supply laminated glass? Is it available with low-E or SunGuard coatings?
Guardian manufactures architectural laminated glass in a variety of thicknesses and sizes and many of the SunGuard Advanced Architectural glass can be laminated. For specific enquiries please contact your local Guardian architectural glass representative.
12. What is roller wave distortion ?
In order to ensure the correct properties of thermally toughened and heat strengthened glass they must be heated to above their softening point, usually in a horizontal roller hearth plant. When the temperature of the glass is above 650°C it becomes pliable and when the glass is oscillating back and forth in the heating stage it momentarily stops at each reversal. It is at this point that the glass between the rollers will slightly sag, resulting in a slight deviation from flatness which reveals itself as ripples or roller wave when viewed at an acute angle in reflection.
This is inevitable and even though the processors strive to minimise the effect, it is an inherent part of the process.
13. What is strain pattern?
The strain pattern refers to a pattern of geometric iridescence or regular dark shadows that appear under certain lighting conditions, specifically when levels of polarised light are high. The technical name for this phenomenon is anisotropy. The cause is localised stress imparted during the rapid air cooling of the glass during toughening or heat strengthening and is not considered a defect.
Guardian does not manufacture spandrel panels, although we do offer advice on the use of SunGuard coatings for use in spandrel glass solutions. Designs where large areas of glass are installed, such as curtain walling and structural systems, often include spandrel panels. Depending on the design the spandrel colour may be selected to match the vision glazing providing a ‘look-a-like’ system where the spandrel and vision glazing look similar when viewed from outside the building. Alternatively the spandrel may be coloured to provide contrast.
Spandrel glass must always be toughened or heat strengthened to avoid thermal stress breakage.
Matching spandrel glass to vision glass with a high light transmission or low reflection can be difficult. The degree of colour and visual similarity can vary greatly depending on a number of factors including; light transmission, time of day, weather conditions and interior lighting and shading.
In general, glass with high light transmission is most suited to contrasting spandrel panels, whereas glass with a low light transmission and higher light reflection are more easily matched to the spandrel panels. We always recommend that you view a full size outdoor mock-up for assessment of the visual appearance and approval of vision and spandrel glass. Generally speaking, matching spandrel glass to vision glass that’s either high-transmittance or low-reflection can be difficult.
Guardian does not manufacture fire resistant glass.
Guardian is a primary glass manufacturer with many float lines, laminating plants and coaters around Europe. We supply our products to a network of independent processors who then supply glass to the final specification. Guardian recommends that you contact your SunGuard Select Processor for further information and assistance with your project costing.
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