Row 1- Acceptable. Row 2- Marginal. Row 3- Harmful. In conditions where excessive thermal stresses may occur, tempering or heat-strengthening glass increases glass edge strength and decreases the chances for thermal breakage. Mid-American Glass, Inc. Glazing Guidelines. Glass Handling and Storage Care must be taken during the handling, transportation, and glazing of insulating glass to insure that edge damage does not occur.
Do not allow the glass edges to contact the frame or any hard surface during glazing installation. A rolling block should always be used when rotating glass to prevent corner damage. Store crated glass in a cool, dry, shady and well-ventilated area where it will not be subject to rain or direct sun. If glass must be stored outdoors, cover with waterproof plastic or canvas in such a manner as to allow air circulation around glass.
This is required to minimize the potential for condensation which could cause staining of the glass. The development of the float glass process in the s allowed the economical mass production of high quality flat glass and virtually all architectural glass is now produced by this process. The vast majority of new windows, curtain walls and skylights for commercial building construction have insulating glazing for energy efficiency and comfort.
This glazing Chapter is complementary to the other fenestration sections of the Design Guide. Architectural glass comes in three different strength categories. Annealed glass is the most commonly used architectural glass.
Because it is not heat-treated and therefore not subject to distortion typically produced during glass tempering, it has good surface flatness. On the downside, annealed glass breaks into sharp, dangerous shards. Heat-strengthened and fully-tempered glass are heat-treated glass products, heated and quenched in such a way to create residual surface compression in the glass.
The surface compression gives the glass generally higher resistance to breakage than annealed glass. Heat-strengthened glass has at least twice the strength and resistance to breakage from wind loads or thermal stresses as annealed glass.
The necessary heat treatment generally results in some distortion compared to annealed glass. Like annealed glass, heat-strengthened glass can break into large shards. Fully-tempered glass provides at least four times the strength of annealed glass, which gives it superior resistance to glass breakage. Similar to heat-strengthened glass, the heat-treatment generally results in some distortion. If it breaks, fully-tempered glass breaks into many small fragments, which makes it suitable as safety glazing under certain conditions.
Laminated glass consists of two or more lites of glass adhered together with a plastic interlayer. Because it can prevent the fall-out of dangerous glass shards following fracture, it is often used as safety glazing and as overhead glazing in skylights.
The plastic interlayer also provides protection from ultraviolet rays and attenuates vibration, which gives laminated glass good acoustical characteristics. Because laminated glass has good energy absorption characteristics, it is also a critical component of protective glazing, such as blast and bullet-resistant glazing assemblies.
Coated glass is covered with reflective or low-emissivity low-E coatings. In addition to providing aesthetic appeal, the coatings improve the thermal performance of the glass by reflecting visible light and infrared radiation. Tinted glass contains minerals that color the glass uniformly through its thickness and promote absorption of visible light and infrared radiation.
Insulating glass units ig units consists of two or more lites of glass with a continuous spacer that encloses a sealed air space.
The spacer typically contains a desiccant that dehydrates the sealed air space. The air space reduces heat gain and loss, as well as sound transmission, which gives the ig unit superior thermal performance and acoustical characteristics compared to single glazing. Most commercial windows, curtain walls, and skylights contain ig units. Most perimeter seals consist of a combination of non-curing typically butyl primary seal and cured frequently silicone secondary seal.
The service life of an ig unit is typically determined by the quality of the hermetic sealants installed between the glass and the spacers, and the quality of the desiccant. Glass and glazing selection play a key role in determining the overall building's thermal performance.
Fenestration thermal performance requirements must be integrated with the design of the building's heating and cooling systems. Single glazing has poor thermal performance and is suitable only for applications where thermal performance is irrelevant, such as interior applications or installations where interior and exterior temperatures do not vary substantially. The vast majority of architectural glazing consists of ig units. Low-emissivity low-E coatings limit heat gain through the glazing by reflecting heat energy.
Reflective coatings reduce interior solar heat gain by reflecting solar energy. Thermal performance of glazing is expressed by its thermal conductance, which a measure of air-to-air heat transmission due to thermal conductance and the difference between indoor and outdoor temperature. Conductance is expressed in terms of U-value. A lower U-value indicates reduced heat transfer through the glass. Thermal modeling of specific fenestration assemblies using computer programs such as THERM allow estimation of total U-values for fenestration assemblies and help predict thermal performance.
Since glass itself is impervious to water penetration, glazing waterproofing performance is determined by the glazing method chosen e. Wet glazing most commonly consists of a gunable "wet" sealant installed over a preformed tape or gasket.
Dry glazing systems utilize extruded rubber gaskets as the glazing seals. This system is also referred to as compression gasket glazing because the system relies on compression of the glazing gasket to seal against air infiltration and water penetration. The systems are sometimes mixed, most commonly with exterior wet glazing and interior dry glazing. Condensation occurs if the temperature of interior frame or glazing surfaces falls below the dewpoint temperature for the interior air.
Glazing strategies for limiting condensation include providing glazing with a low U-value and providing supplemental heat to the glazing to increase surface temperatures.
Glass appearance is influenced by several factors, including tinting colorants added to the glass batch , reflective and low - E coatings, and opacifiers for spandrel glass. Acoustic performance of exterior building envelope assemblies is expressed in terms of the Outdoor—Indoor Transmission Class OITC rating, which is a measure of the sound transmission loss during standard tests.
High sound transmission loss, and therefore good sound insulation, is desirable in most applications. An integrated strategy to limit sound transmission through building walls requires review and testing of the entire wall system, since even small discontinuities in the wall assembly can negate the benefits of a well designed glazing system with a high OITC rating.
Publication is planned for early The BEC division hopes to publish the bulletins in early The edition provides a substantial update of product technology and industry standards. Members are purchasing the manual for their internal use, as well as for distribution to their customers.
The fourth edition was published in , and the course has more than students enrolled and active in continuing their education.
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