According to Wikipedia, the term “glazing” is derived from the middle English for “glass”. Wikipedia says glazing “is a part of a wall, made of glass. Glazing also describes the work done by a professional “glazier”. Glazing is also (less commonly) used to describe the insertion of ophthalmic lenses into an eyeglass frame.”
“Common types of glazing that are used in architectural applications include clear and tinted float glass, tempered glass, and laminated glass as well as a variety of coated glasses, all of which can be glazed singly or as double, or even triple, glazing units. Ordinary clear glass has a slight green tinge but special clear glasses are offered by several manufacturers.”
“Glazing can be mounted in a window sash or door stile, usually made of wood, aluminium or PVC. The glass is fixed into a rabbet (rebate) in the frame in a number of ways including triangular glazing points, putty, etc. Toughened and laminated glass can be glazed by bolting panes directly to a metal framework by bolts passing through drilled holes. Glazing is commonly used in low temperature solar thermal collectors because it helps retain the collected heat.”
The term "glazing", using transparent materials like glass, is also relevant to doors that are made of glass or have glass windows integrated into them as well. Whilst there are many types of glazed windows and doors in the US (i.e. wood, steel, composite, aluminium), contemporary thermally efficient, secure and aesthetically pleasing replacement windows and doors have become the products of choice due to their “unique” benefits.
When a door or window is described as "double glazed", it means that it has two layers of glass fitted into it. This doesnt mean that the glass pane used is twice as thick as a regular glass pane; the two panes are set in an air-tight frame and separated by a gap. This gap, which can be several millimetres thick, acts as an additional layer of protection for your home.
Modern energy rated double glazed windows and doors offer benefits “old” windows and doors struggle to deliver, including protection for external pollution (i.e. smoke, dust, smells, pollen and noise), thermal efficiency and heat insulation.
Firstly, energy efficiency - A contemporary energy rated double glazed product is highly thermally efficient, due to its design and the current Building Regulations legally requiring any replacement windows and/or doors to meet higher energy saving standards. Consequently, if your property is well-insulated, you will spend less trying to heat it during winter or in keeping it at a pleasant temperature during summer months, thereby saving energy.
Secondly, heat insulation - Thermally efficient double glazed windows and doors are highly effective heat insulators for your home. Their layers of insulation prevent too much heat entering a home during summer, while preventing heat from leaving a house during winter. Most companies that manufacture double glazing fill the gaps between the two panes of glass with clear, non-toxic gases like Krypton and Argon. These gases are denser than regular air, thereby increasing the double glazed windows or door’s insulating performance.
Thirdly, pollution protection - Double glazing has sealed units with virtually air tight frames and two layers of glass, so is extremely effective in keeping out pollen, dust particles, smoke and other air-borne pollutants out of any home.
Finally, noise reduction - Homes near main or busy roads, can be badly affected by heavy traffic (including carbon monoxide pollution), with disruptive traffic noise disturbing home life. Many residents resort to expensive “soundproofing” of walls and adding secondary glazing, but the results can be disappointing. Secondary glazing frames do not have a thermal break, plus take up most space within any window reveal, so it is often more practical (as long as your property is not listed or in a conservation area) to fit double glazed windows and doors.
By specifying that one of the two glass panes is made of slighter thicker laminated glass, the two different thicknesses of glass, along with the air-filled gap found in between double glazed sealed units will reduce and muffle sounds coming from outside a property.