Low-E (Energy Saver)
Did you know?
By using certain Low E glass combinations, more than two thirds of the heat can be eliminated prior to it entering the building.
Low E (Low emissivity) coated glass is designed to improve thermal insulation in both summer and winter. Low E coated products result in a lower U-value. The lower the U-value the better the performance. As warm air is always drawn towards cooler air, a Low E coating will reduce heat gain when the air outside is warmer than the air inside and reduce heat loss when the air inside is warmer than the air outside. A Low E coating on clear glass will have little effect on reducing the impact of the sun's direct heat (solar energy).
how low-E glass works on cold days
Typical oil bar heater energy and stored energy being released from floors (this stored energy may passively collect during the day from the sun's direct transmission).
The Low-E coating assists in reflecting this heat back inside.
How low-E glass works on warm days
Sun's direct intensity, short wave infrared heat energy, strikes the glass surface and surroundings converting this energy into long wave (low energy) infrared heat.
The Low-E coating assists in rejecting this heat back outside.
Single glazed monolithic low-E
Low-E glass was primarily designed for use in IGU's. However, there has been an increasing demand for use of low-E coated glass such as Sunergy® as single glazing.
Sunergy® is the ideal choice for most Australian climatic conditions providing improved solar and thermal control.
Sungate® 500 is best used in laminated form with a body tint glass or tinted PVB to improve solar and thermal control functions where windows have direct unwanted exposure to the sun.
Coating position – See Diagram 3.4.
Improvements of up to 30% in the U-value can be achieved with the low-E coating on surface position #2 for single monolithic (see Fig 1) and #4 for laminated glass (see Fig 3). No improvements in U-value are achieved with the low-E coating on surface position #2 or #3 for laminated glass. Low-E coating placement on surface position #1 should be avoided due to effects of weathering and pollutants and subsequent cleaning difficulties.
However, you do get a reduction of direct heat gain through lower SHGC with the coating in any surface position.
IGU's – insulated glass units
Sunergy® is the ideal choice for most Australian climatic conditions providing improved solar and thermal control. Adding a low-E coating to surface position #2 acts like an additional barrier by further slowing the rate of the heating of the air gap. Having the coating on surface position #3 allows the air gap to be heated more quickly, because the low-E surface position #2 barrier is removed. This reduces the performance of the glazing
in terms of heat gain to the interior of the building.
See Diagram 3.4 – Fig 2.
Where retention of heat is a priority, the low-E coating on surface position #3 is recommended. In these situations we are relying on the effects of passive solar heat gain to naturally heat the building's interior and the low-E coating to reflect any of the re-radiated heat back into the room. Best product selection would be Sungate® 500 or soft coat single or double layer low-E coating.
See Diagram 3.4 – Fig 2.
Low-E must be air side to improve U-value
Low-E coating placement on surface position #2 or #3 of a laminated pane will not improve the U-value as the coating is now in direct contact with the PVB and the glass (see Fig 3).
Any re-radiated heat will now be conducted through PVB, coating and glass. The low-E coating must be air side to improve U-value. However, as previously noted, low-E coatings in any position placement will improve the SHGC.
- For commercial buildings withlarge expanses of glazing that require the highest performance in environmental control for energy savings, yet retain transparency.
- Curtain wall & large
- Glazed facades
- Commercial buildings
- High rise apartments
- Institutional and social buildings
- Residential homes
- Homes renovations
- Replacement glazing