Large light glazing speaks to what is large light glazing and why use large light glazing.
It is large lights, those over 6 square feet (0.06 sq m) in area which require more glazing.
Wind load stresses on each light of glass are higher and the glass must span farther between its supporting edges. Any irregularities in the frame of the window may result in distortion of the glass, highly concentrated pressure on small areas of the glass, or glass to frame contact, amy of which can lead to abrasion or fracture of the glass.
In large lights, thermal expansion and contraction can also cause stresses to build up in the glass.
The design objectives for a large light glazing system are:
To support the weight of the glass in such a way that the glass is not subject to intense or abnormal stress patterns.
To support the glass against wind pressure and suction.
To isolate the glass from the effects of structural deflections in the frame of the building and in the smaller framework of mullions that support the glass.
To allow for expansion and contraction of both glass and frame of the window or with any other material that could abrade or stress the glass.
To avoid contact of the glass with the frame of the window or with any other material that could abrade or stress the glass.The weight of the glass is supported in the frame by synthetic rubber setting blocks, normally two per light, located at the quarter points of the bottom edge of the light. For support against wind loads, a specific amount of bite, which is depth of grip on the edge of the glass, is provided by the supporting mullions.
If the bite is too little, the glass may pop out under wind loading, if too much the glass may not be able to deflect enough under heavy wind without being stressed at the edge. The mullions of course must be stiff enough to transmit the wind loads from the glass to the frame of the building without deflecting so far as to overstress the glass. The resilient glazing material used to seal the glass to mullion joint must be of sufficient dimension and elasticity to allow for any anticipated thermal movement and for possible irregularities in the mullions.
The glazing materials that are most commonly used between the mullions and glass include wet glazing components and dry glazing components. The wet components are mastic sealants and glazing compounds. The dry components are elastomeric gaskets. Wet glazing with good workmanship is more effective in sealing against penetration of water and air. Dry glazing is faster, easier and less dependent on workmanship than wet glazing. The two types are often used in combination to utilize the best properties of each.
Glazing materials used are:
Pre-shimmed butyl or polyisobutylene tape Acrylic pr butyl sealant Butyl or polyisbutylene tape, Cellular neoprene, Dense neoprene roll-in gasket Dense neoprene gasket High range sealants such as polysulfide, silicone or acrylic sealant. Dense neoprene roll-in rod Cellular tape