Insulated Glazing
Insulated Glazing or otherwise known as double 
(or triple, depending on the no of panes)
glazing is a very important constructional feature of
buildings in terms of heat energy conservation.
Glazing is an essential item in modern architecture and building construction.
Incorporation of glazing brings about aesthetic beauty and an interior
environment with a natural and an open space feeling to the occupants.
However there is a major drawback due to glazing.
Compared to thick brick and plaster walls, the thin glass is rarely thicker
than 6 mm, which permit heat energy transfer from the warm areas to the cooler
areas in vast quantities, while draining out your hard earned money along with it.
Studies carried out in the US have shown that approximately 30%
of all the heat lost through the envelope of a building is due to the glazing of windows and doors.
The double glazing, triple glazing or the various other improvements thereof, with high R values
however reduce the costly thermal energy loss significantly.
What is Double or Triple Glazing?
Double or Triple Glazing, also known as Insulated Glazing Units or IGUs are glazing incorporating
two or more glass panes entrapping a gap filled with an inert gas (usually argon) or in the alternative
a totally evacuated and sealed space.
Simply put, they employ two major heat loss prevention techniques found in vacuum flasks,
namely blocking of conduction and convection. Interestingly, the latest vacuum type triple glazing
(R value up to 13) uses the third method of blocking of heat transfer too by inhibiting radiation
with a low emissivity coating, thus emulating the properties of a vacuum flask.
How do you measure insulation property of Glazing?
Insulation property of glazing (or any substance for that matter) is spoken of in terms
of R value. R value is the quantity of heat transmitted through 1 m2 of a substance
when the colder and hot surfaces are subjected to a temperature difference
of 1 degree Kelvin (numerically equivalent to 1 degree Celsius).
The R value of plane double glazing is between 1 to 2.That of double
glazing without a low emissivity coating and filled with Argon gas is about 3
while that of triple glass with low emissivity coating and Argon gas fill is approximately 5.
As mentioned before the R value of vacuum type triple glazing with low emissivity coating is up to 13.
In contrast a well constructed brick and plaster wall would have a R value of about 12.
Ideal Glazing
Ideal Glazing, if there is such thing, should exhibit all or at least a
substantial number of the following:
- High R value (ie a good insulation)
- High VT value (Visual Transmittance value indicating good visibility through)
- Low overall weight
- Low overall thickness
- Long lasting construction material especially, strong glass sealants, frames, reflective coatings etc.
- Good acoustic insulating property.
- Absence of apparent discoloration generally noticed from outside due to poor low-E coatings
Construction of different Insulated Glazing types
Whatever the number of lites or panes the basic constructional features remain similar.
The thickness of the glass panes may vary from 3mm to 10 mm but could be still thicker
depending on various special applications. The glass material itself may be tempered or laminated.
The thickness of one pane (or more) of glass may be different to the others due to economic reasons.
Special precautions are taken during manufacture to avoid shearing effect as this the major cause of glazing failure.
To improve the quality of performance and for aesthetic effect, tinted glass, polyester or metal coated
glass and low emissivity coated glass are used in the manufacture.
A spacer is used between glass lites to maintain the optimum clearance in between them and inert gas filling.
The spacers are either of metal or structural foam material.
The latter is the preferred material from the point of view of energy conservation.
A desiccant such as silica gel is used with the spacers to remove the moisture from the enclosed chamber.
An adhesive type sealant, generally polyisobutylene, is used to seal all gaps of possible leaks in the IGU.
A clearance of 16 mm-19 mm is maintained between panes for 3 mm glazing and 28 mm – 31 mm for 6 mm glazing.
IGUs are made to order due to differences in dimensions in building structure etc.
Therefore it is necessary to provide the width, height, thickness of glazing and required qualities,
along with its overall thickness to the manufacturers with your order.
Greentech.ie is your friendly advisor for double or triple glazing in Ireland.
Consult them at no cost to you for your ongoing or future project and how to save
on your energy bills all the while deriving a ton of other benefits as well.
