Windows and glazing have been a considerable loss factor in the energy balance of a building, as single panes do not provide sufficient thermal insulation.  A solution is to use insulating glass.

An insulated glass unit consist of 2 or more pieces of glass separated by an air space.  The space between the glass is hermetically sealed using either swiggle tape or alumunium spacers.  This space contains air at atmospheric pressure which is kept dry by a desiccant within this spacer.

Thermal Insulation

The low heat conductivity of the dry air between the insulating glass cuts down the energy transfer trough radiation while the small space between the panes limits the energy transfer trough convection.

Acoustical Insulation

The air space also attenuate sound waves which results in greater sound insulation.

Air space available:

• 6 & 12 mm (other thickness available upon request).
• Silver (other colors available upon request).
• Minimum size:  300 x 300 mm
• Maximum size:  3048 x 2250 mm

Comparative Performance Data

Glass	Thickness MM	V ref %	V trans %	S ref %	S trans %	S abs %	RHG W/m²	Sum K W/m².K	SC
Clear float	6	8	89	7	79	14	554	5.01	0.95
Clear float	12	8	86	7	69	14	506	4.93	0.86
Clear 6 + 6 AS + Clear 6	18	14	80	11	63	26	543	3.48	0.82
Clear 6 + 12 AS + Clear 6	24	14	80	11	63	26	542	3.12	0.82
Tinted dark blue	6	6	58	5	43	52	398	5.39	0.66
Tinted dark blue	12	5	36	5	23	72	296	5.23	0.47
DHFL 6 + 6 AS + Clear 6	18	9	52	6	34	60	360	3.57	0.53
DGFL 6 + 12 AS + Clear 6	18	9	52	6	34	60	360	3.57	0.53
Reflective dark blue	6	30	43	22	34	44	320	5.27	0.51
Reflective dark blue	12	29	28	21	18	61	252	5.23	0.39
SSDH + 6 AS + Clear 6	18	31	39	23	27	50	294	3.52	0.42
SSDH + 12 AS + Clear 6	24	31	39	23	27	50	288	3.17	0.42

K value (U value) is the overall coefficient of heat transmission or heat flow.  Lower K values indicate better insulating performance.  The tint or reflectivity of the glass does not have much effect on the K value.  In other words, 1 piece of 12 mm tinted glass does not give better insulation than 1 piece of 12 mm clear glass.

Shading coefficient is the ratio of the total amount of solar energy that passes trough a piece of glass with respect to a 3 mm thick clear glass under the same conditions.  Lower shading coefficient values indicate better performance in reducing heat gain.  Usually, the shading coefficient is affected by the tint or reflectivity of the glass.  The darker the glass usually means the lower the shading coefficient (but has little effect on the K value)

 

Using a clear glazed unit reduces the K value by at least 30% in comparison to a single glaze.  This means that the IGU provides 30% better insulation, reducing the initial investment costs for the cooling or heating equipment, and saving energy costs throughout the year.

Percentage reduction of K value

Glass Type	Thickness	K value	%
Clear glass	12 mm	4.93	-
Clear IGU	18 mm	3.48	30
Clear IGU	24 mm	3.12	37