GLAZED WINDOW SHUTTER (TYPES & SPECIFICATION)

Glazed windows can be generally categorized as:

   

       Single glazing

The window system should be provided with suitable water drainage facility. Shutters of same materials and color should be fitted with approved quality friction stay and handle with locking arrangements, hinges etc. The system should be factory assembled and fixes at site using anchor fasteners, silicon sealant to be applied at the joint between window system and wall opening for lead proofing, easy glazing, de glazing at site, etc.

·     Dubble glazing

In a dual glazing system two single glass panes are set individually into an aluminium or wood window sash. The glazing system is integral to the window design, and the air space between the panes is typically vented to the exterior. Consequently, the space between the panes cannot be filled with an inert gas since it would escape through these vents.

Instead of sealants dual glazing relies in a gasket and vent system design to keep moisture out of the air space and from forming on the internal glass surfaces. This system is often used o projects where the building owner wants blinds places between the panes.

The dual glazing concept has also been used in several recent projects incorporating a double-skin façade which comprises a pair of glass separated by a fairly large air space. Ultimately the space acts as a buffer against sound, temperature extremes, and wind. It typically contains shading devices and is vented to the exterior.

Selection criteria

Various criteria ranging from thermal performance to sound transmission requirements can be used to determine which glazing system is most appropriate for a specific project. In some cases the size of the glass needed or the project fenestration design actually dictates which system is suitable.

In terms of aesthetics, cost, and thermal performance both single and double glazing offer similar advantages. However single glazing accommodates a wider range of fenestration types and larger glass sizes, while dual glazing offers a warmer edge, longer life, easier re glazing, between glass options, less sound transmission, and better thermal performance when between glass blinds are included.

1.     Glass size and fenestration type

Single glazing glass is typically available in sizes up to approximately 1200mm*1200mm with 1200mm*500mm fixed ventilator at top. Total size is 1200* 1700. The size of glass in a dual glazing system in the other hand is typically available in sizes smaller than 1200*1200, as it is limited by the interior glass access panel’s structural design.

The dual glazed fixed windows are in more commonly used in operable or fixed windows. However they can still be used to create the appearance of a store front or curtain wall, when joined together in groupings. The glass should be free from specks, bubbles, blisters, veins air holes, etc.

·       Putty: It is used for fixing the glass in wood frames (IS-419-1953) and for glazing (IS-420-1953)

·       Mastic: It is used instead of putty, Glass bricks shall be laid in mastic in 1:3 cement mortar if so specified in special provisions.

·       Rails and Mullions: They are jointed to styles, styles continuous from top to bottom. Thickness of the frame vary from 32mm to 50mm or as per required. Grooves or putty shall be made in all insides faces of the frame to receive glasses.

2.     Fixing: Fixing pre-fabricated openable casement windows of homogeneous materials multi chambered with outer wall of minimum size 60mm*56mm, thickness not less than 25mm, reinforced with hot dip 120 galvanized steel of minimum thickness 2mm.The pre fabrication must be fusion welded and be capable of mounting single gazing with 5mm clear glass and double gazing with 5mm clear glass + 8 to 12mm air gap + 5mm clear glass. The glass shall be embedded in putty externally, wash leather, velvet, felt, rubber or other approved by the engineer internally.

3.     Curing: The frames shall be primed and plained with different sand papers and painted so that the wood may not draw oil out of the putty and putty may adhere properly. Putty may be given a coat of oil paint to match side surfaces, sealing the edges of putty and its setting time 7 days.

4.     Rate: The rate for finished item shall include cost and conveyance of all materials to site, labour charge, scaffolding and equipment to carry out the item, fixing the glass including cutting extra waste, cleaning the glazed work and repairing of damaged work during glazing.

5.     Thermal performance and warm edges

A window’s thermal performance can also be an important factor in specifying a glazing system for a project. The key thermal criteria to review when selecting a system are:

·       U value: measure of the rate of mom solar heat loss/gain through a material/assembly (a lower number means the material is a better insulator)

·       Visible light transmission: percentage of visible light(380 nm to780 nm) transmitted through the glass(a higher number is better)

·       UV light gain coefficient: percentage of UV light(300 nm to 380nm) transmitted through the glass(a lower number is better).

·       Solar heat gain coefficient: measure of incident solar radiation entering a building through the window as heat gain.

                   Clear dual glazing offers a better total window U value than single one while all other values are same. With the blinds closed dual glazing offers an 18% improvement in total window U value and a 43% improvement in solar heat gain coefficient. With the advent of low emission glass wintertime center glass temperatures have become so warm that cooler edge conditions have a mare dramatic impact in the total window U value.

6.     Sound transmission

There are three primary factors affecting sound transmission through windows:

·       Glass thickness

·       The size of the air space between the panes of glass.

·       Damping of the glass (typically associated with laminated materials).

When comparing single to dual glazing, the only differing acoustic factor id the sir space between the paned of glass. The larger air space associated with dual glazing results in less sound transmission through the window and a sound transmission through the window and a sound transmission class (STC) rating at least 15% better, with additional improvements in STC as the air space increases.

7.     Longevity and re-glazing

When specifiers or building owners look for a glazing system to last as long as the building/window, they may want to consider dual glazing as a more sustainable option- replacing failed gaskets is less expensive.

Less than 1% of the glass in most buildings experience breakage, but in buildings where this is an issue, the specifier and building owner may want to consider dual glazing to reduce life cycle costs.

There are many factors to consider when specifying a structure’s glazing system. In most cases, the project requirements determine which glazing system is most appropriate. Fenestration type, glass size, and aesthetics are important factors whereas oftenly life cycle costs, long term durability, and the reduced maintenance are important.