Glass Options
Glass Types & Weights
Clearview aluminium secondary glazing is available with a range of glass options, including toughened, laminated and a choice of obscure finishes. There are choices for thermal, security, acoustic and privacy. Our standard option is 4mm toughened glass, giving enhanced safety and security – and, of course, meeting Building Regulations.
Given the range of glass choice it is understandably a confusing area as to which is the right glass for you. It is also very common for the glass to be considered as critical to the performance, whilst it is important it may not be as significant as you may think. You may end up paying more than you need or be put off purchasing when comparing prices without a full grasp of the facts.
At Clearview, we want you to get the best advice for your specific and individual needs maximising the best performance within an affordable budget.
The number one insulation performance enhancement is simply installing Clearview Secondary Glazing, the glass is then just fine tuning to optimise the final benefit. To get the best outcome, we recommend:
- For sound proofing: maximise the glass to glass air-gap, if you can achieve 100mm or greater, 150mm to 200mm is the best. Then subject to your individual sensitivity to the noise problem and budget, choose a thicker glass. If your window design is such that a reasonable gap is not possible, then a thicker or acoustic glass can offset some of this distance limitation. If you compromise the air-gap you will compromise performance. How to Optimise Soundproofing [click here]
- For Thermal Insulation: The air-gap is less critical and we recommend 50mm to 80mm as a reasonable distance. Glass thickness is also far less important for thermal insulation and will do little to keep more heat in or cold out. Using a Low-E (low emissivity glass) can offer a 5% to 10% enhancement over standard glass but is affected by the condition of the primary window. How to Optimise Thermal Insulation [click here]
- Condensation: following the above thermal principle is the same for tackling condensation, whilst secondary glazing cannot guarantee complete eradication of the problem, it does have a very good track record of significantly reducing the problem and enabling a far more effective management option. How to tackle Condensation [click here]
- Safety & Security: All our glass options conform to BS EN 12600 for impact resistance. Toughened and laminated glass are very good security enhancements, laminates in particular – just by secondary glazing being installed, would-be intruders are often put off attempting a break-in as they see a second layer of defence and a further obstacle to tackle, they usually move on to a less challenging window. How to increase Security [click here]
Glass Options for Secondary Glazing
4mm Toughened
This is our entry level product, a good starter for general use. It can offer around a 50%+ enhancement in thermal insulation and with the right air-gap 45dB sound reduction. If your primary window is assumed to be 4mm or you have standard double glazing, we recommend trying to mix glass thickness. 4mm toughened glass is 2–4 times stronger than ordinary glass (float/annealed glass) of the same thickness. This safety glass is a minimum requirement where building regulations demand health and safety considerations, including the distance from floor and doors.
6mm Toughened
This is 50% more material than the 4mm option. It can offer around a 50%+ enhancement in thermal insulation and provides excellent sound reduction performance, with the right air-gap 49dB+. 2–4 times stronger than ordinary glass (float/annealed glass) of the same thickness, providing enhanced security and health & safety.
Obscure Toughened
Privacy textured glass, e.g. bathroom windows, available in 4mm and 6mm toughened thicknesses, offering the same performance values as detailed above. See below for design options.
Satin Toughened
Frosted effect Privacy glass providing a higher degree of obscurity to textured glass. Available in 4mm or 6mm toughened thicknesses. Providing the same performance values as the above 4mm & 6mm options.
Low E (emissivity) Toughened Glass
(Widely known as Pilkington K glass.) This is a thermal performance enhancing coating applied to the glass. An invisible, proven technology capable of increasing the insulation performance of the glass by 65% – up to 10% more than a non-coated option, equivalent to a mid-ranged double glazed sealed unit with a certificated U-value of 1.868 W/m²K. With special thin-film metallic or oxide coating allowing short-wavelength solar energy to be transmitted into a building, but preventing long-wavelength energy of the heating systems from escaping; so conserving heat, it also reduces UVA & UVB solar radiation. Available in 4mm, 6mm toughened glass and 6.4mm Laminated glass. This is a hard coat application with a degree of robustness, but can be scratched if abrasive cleaning materials are used – see maintenance.
6.4mm Clear Laminate
2 sheets of 3mm plate glass with a sheet of 0.4mm transparent ethylene-vinyl acetate (EVA) between, moulded together under heat and pressure. The glass will crack without shattering – also known as shatterproof glass. Considered a Class B safety glass (2B2). Enhanced sound proofing properties, equivalent or marginally better than a 6mm version.
6.4mm Clear Acoustic (Stadip Silence)
Specially developed acoustic glass comprising a PolyVinyl Butyral (PVB) interlayer which acts as a dampening core to prevent sound frequencies from vibrating from one pane of glass to the other. This absorbs and weakens sound energy, helping to act as a barrier to noise. This plastic interlayer also has the additional safety and security properties of laminated glass. Considered a Class B safety glass (2B2). Stadip Silence acoustic glass offers optimum sound reduction performance – approx 51 dB to 53 dB is possible. However, it is a premium product and priced accordingly.
6.8mm Clear Laminate
2 sheets of 3mm plate glass with a sheet of 0.8mm transparent ethylene-vinyl acetate (EVA) between, moulded together under heat and pressure. The glass will crack without shattering – also known as shatterproof glass. Considered a Class A safety glass. Enhanced sound proofing properties, equivalent or marginally better than 6mm or 6.4mm versions.
6.8mm Clear Acoustic (Stadip Silence)
Specially developed acoustic glass comprising a PolyVinyl Butyral (PVB) interlayer which acts as a dampening core to prevent sound frequencies from vibrating from one pane of glass to the other. This absorbs and weakens sound energy, helping to act as a barrier to noise. This plastic interlayer also has the additional safety and security properties of laminated glass. Considered a Class A safety glass (1B1). Stadip Silence acoustic glass offers optimum sound reduction performance – approx 51 dB to 53 dB is possible. It also has a slightly better performance with higher frequency sounds. However, it is a premium product and priced accordingly.
Glass vs Benefits Matrix
| Glass Type | Thermal | Acoustic | Safety |
|---|
Help with Calculating Glass Weight
Below is the glass weight calculation formula, to help you choose the correct glass weight for your secondary glazing. See the size guide page and the download on this page, for minimum and maximum unit sizes for all products in Clearview’s Classic and Forte ranges.
Minimum and maximum suggested unit sizes »
If you need any more assistance, email us with sizes of the required unit.
Glass weight = 2.5kg × mm glass thickness × unit m²
e.g. unit 950mm × 1200mm = 0.95 × 1.2 = 1.14 m² with 6mm glass. Calculation is 2.5 kg × 6mm = 15kg × 1.14 m² = 17.1 kg weight.
| Glass Type | Weight per m² |
|---|---|
| 4mm Glass | 10 kg / m² |
| 6mm Glass | 15 kg / m² |
| 6.4mm Glass (Laminate / Acoustic) | 16 kg / m² |
| 6.8mm Glass (Laminate / Acoustic) | 17 kg / m² |
| 8.8mm Glass (Laminate / Acoustic) | 22 kg / m² |
| 10.8mm Glass (Acoustic) | 27 kg / m² |
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