27
80dB whereas a reasonable internal level for a meeting room during the day is 35-40dB. Most existing single glazed windows will reduce noise levels
by 25-30dB and even modern double glazed windows will nor- mally only achieve 30-35dB, often not enough to create a com- fortable environment. Secondary windows can reduce noise lev- els by 45-50dB. The internal window is set with a minimum air gap of 100mm and this decouples the two glass panes and reduces noise transmission. The greater the cavity the better the dampening effect. A further benefit of secondary glazing is increased security
and property owners and managers must consider their duty of care to those using the building.
Physical attack “Secured by Design” accreditation and testing, in accordance with standard BS7950, guarantees resistance against stealth attack on lower risk premises. Where the risk is greater and the glass element is likely to be forcibly attacked, products should be tested to the Loss Prevention Certification Board’s standard LPS1175. There are a number of certified levels measured in terms of the attack tools and the time available to the attacker. Glazed products tested up to Level 3 will offer a secure option to heavy-duty bars and grilles without the visual intrusion.
Fire rating Secondary windows may be needed for vulnerable areas such as windows adjacent to fire escapes. Fixed frame aluminium sys- tems are available tested to 30-minute integrity. Higher ratings currently require the use of steel sections.
Window styles Secondary glazing is available in a wide range of styles including horizontal sliding, balanced vertical sliding, hinged and fixed. The best material is aluminium, a strong versatile metal that can be extruded into complex shapes and readily formed to deal with the curved windows that are often found in traditional build- ings. Framing sections are powder coated to provide a perma- nent finish and almost any colour can be accommodated.
Professional delivery As with all elements of a refurbishment, a successful outcome needs careful up-front design and close project management. Secondary windows are purpose made to precisely fit each win- dow opening and fully fabricated and glazed off-site. The use of lean processing methods and rapid installation allows flexible programming with minimal snagging and will support the very tight programmes that clients often need.
By Selectaglaze Ltd. 131
From top: Birmingham’s Town Hall; the Supreme Court (image courtesy of Tim Imrie)
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60