Glass building codes speaks to what are glass building codes and why glass building codes.
These codes are concerned with several functional aspects of glass.
These are its structural adequacy against wind and impact loads, its role in providing natural light in habitable rooms, its breakage safety, its safety in preventing the spread of fire, its safety in preventing the spread of fire through a building and its role in determining the energy consumption of a building.
The International Building Code provides structural criteria for determining the necessary thickness of glass to resist wind and other structural loads. In coastal regions where hurricanes are common, the code also requires windows or window coverings to meet requirements for resistance to the impact of objects that may be blown against glazed areas by high winds.
The International Residential Code requires all habitable rooms to have a net exterior glazed area equal to at least 8 percent of their floor area. The International Building Code does not generally require exterior windows or glazing, with the exception that some bedrooms are required to have emergency escape windows or doors and permits spaces to be lit by artificial illumination alone.
The use of natural light to provide interior illumination and the provision of views to the exterior for building occupants are recognized components of healthy, energy efficient buildings and are encouraged by LEED for new construction and other sustainable design programs.
Breakage safety is regulated in skylights and overhead glazing to avert accidental injury that might be caused by falling shards of broken glass. Laminated glass and plastic glazing sheets, because they eill not drop out of the skylight if broken are the only skylight glazings that are permitted without restriction.
Breakage safety is also important in glazing that people might run into and break with their bodies. To avoid severe injury in such an occurrence, building codes mandate that sheets of glass in hazardous locations must be some type of safety glazing, that is, glass or plastic that does not create large, sharp, potentially lethal spears when it breaks.
Examples of such locations include areas in and around exterior doors where people may accidentally bump against the glass. This includes floor to ceiling sheets of glass that are often walked into by people who mistake them for openings in the wall, shower enclosures, and windows having a glazed area in excess of 9 square feet (0.9 square meters) whose lowest edge is within 18 inches (450 mm) of the floor. Glazing materials that meet safety glazing requirements include tempered glass, laminated glass and plastic sheet.
Fire rated glass must be used for openings in required fire doors and fire separation walls. The maximum areas of glazed openings in these locations are specified by building codes. The International Building Code also requires that windows aligned above one another in buildings over three stories in height be separated vertically by fire resistant spandrels of a specified minimum height, usually 36 inches (914 mm). The intent of this provision is to restrict the spread of fire from one floor of a building to the floors above. If a glass spandrel is used, it must be backed up inside with a material that offers the necessary fire resistance.
Glass building codes provisions relating to glass and energy consumption generally offer several approaches to the designer of a building. Prescriptive requirements may be followed that explain clearly the maximum amount of glass that may be used, expressed as a percentage of the overall wall or floor area and the minimum thermal resistance of the glass.
Alternative methods allow the designer to trade off thermal performance between different parts of the building or to perform a detailed energy analysis of the entire building using approved methods, demonstrating in either case that the overall energy performance of the building is equal or superior to that of the same building designed in conformance to prescribed requirements.