Double-Glazed, Insulated Glass
Ambient heat transfer can occur via three methods; convection, conduction and radiation. The weakest resistance to these mechanisms, in a building envelope, is the glazing material.
By nature, a single piece of glass has little resistance to either heat gain or loss; however, an insulated glass unit (IGU), comprising of two or more panes of glass with hermetically sealed air spaces in between, slows down the rate of heat exchange between the ambient hot and cold air masses on either side of the unit. The resultant reduction in heat transfer minimizes the capital and subsequent operating costs of heating or cooling equipment.
In a Uniglass I.G. unit, the glass panes can be annealed, heat-strengthened, tempered and/or laminated to meet building code requirements, safety glazing standards and design requirements. The panes can be of equal or unequal thicknesses and the most common insulated glass unit setup is constructed with two plies of glass and one sealed air space
Insulated glass is internationally recognized used due to the improvement in solar and thermal performances it may provide. The most significant improvement is most observed in thermal performance (u-value) which is improved by an approximate of 50% when compared to a monolithic glass ply. This improvement occurs whether the glass is coated or uncoated.
|Light transmission: 89%|
|Shading Coefficient: 0.97|
|U-Value: 5.25 W/ (m 2 ⋅K)|
|Light transmission: 80%|
|Shading Coefficient: 0.85|
|U-Value: 2.85 W/ (m 2 ⋅K)|
|Light transmission: 67%|
|Shading Coefficient: 0.62|
|U-Value: 1.9 W/ (m 2 ⋅K)|
In addition to the improved solar performance, insulating glass offers higher compatibility to objective weather conditions and subjective requirements through a greater availability of coatings. Silver-based coatings cannot be exposed and therefore can only be used inside the insulated glass unit where they are protected by the hermetically sealed space.
Insulated glass unit offer more aesthetic possibilities than monolithic glass. Aside from coatings of various colours and functions, silk-screen patterns can also be applied to the exterior ply of glass; leaving the interior ply available for additional treatment. For a spandrel location, a full coverage opaque ceramic frit can be applied to the inner face. For vision areas, where daylight is desired but external visibility to the internal needs to be minimized, a translucent ceramic frit can be applied to the surface facing the airspace.