Solarishield
Solar Blinds & Sun Awnings
Test Report
Tests prove up to 30% better U-value
In the beginning of March 2010, the Swedish official test institute SP in BorĂĄs did a U-value test on the EnergyBlinds solar blinds.
As a comparison, they used an ordinary wooden window frame with a 10 years old standard double glazed cassette. The U-value of the insulating cassette was measured to 2.7, which is OK for a standard window.
When a EnergyBlinds solar blind (EB40 with Blue15 film) was rolled down, the U-value was measured at 1.9, which is an improvement of 30%!
Bertil Jonsson, SP: “If the test had been performed on a brand new, argon filled insulated cassette (U-value 1.3) the improvement would not have been as high as 30%, but it would definitely affect the U-value. Likewise – if the test was performed on a single pane, then the improvement would have been better than 30%”
Definition of U-value and G-value
- Heat loss through a construction material is measured by its U-value.
- A low U-value is the most important quality for both single and double
glazed windows, and results in low heat loss through the window.
- G-value is the measurement of solar heat gain within a building.
- A low G-value means less solar heat gain and reduced cooling costs.
- The best windows, from an energy point of view, will have both a low U-value and a low G-value.
- Windows having better thermal insulation have a higher surface
temperature on the inside face, which improves the comfort of the
room.
Solar heat, which is very much welcome during colder periods, can create in summer months an uncomfortable indoor environment.
The cost of cooling a building can be up to 4 times higher than the cost of heating it in winter. A low g-value is therefore very important when buildings have large glass facades.
A window with an improved G-value is not, however, comparable with a good sunscreen. Standard double glazing has a G-value of approximately 75%. Specially treated glass can reduce the g-value to about 25%, but the can’t be removed when you need the benefits of solar heating during colder months.
EnergyBlinds solar blinds can create a G-value of 20% or less, when added to standard double glazed window – with the advantage of still having a clear vista from the window, and also the possibility of being removed from the window as and when required.
U-value is the measurement of heat loss
Heat loss is specified by the U-value. The U-value is a measurement of how efficiently the combination of glass, frame and sash reduces the heat loss trough the window. (For example, the window’s thermal insulation properties.)
G-value is the measurement of heat gain by solar heat
The G-value is a measurement of heat gain created by solar heat. The sunrays can only enter a building through the glass. The g-value is a measurement of how much solar energy is transmitted through the windows directly and by heat transfer from the glass surface.
An average family home of approximately 144 m2 uses on average 15,000 kWh per year to heat the home. Standard double glazed doors and windows allow 1/3 of this heat to escape.
A standard double glazed window sometimes has the draught effect. This is caused by the inner pane of the window being cold.
Energy efficient windows have a higher inner temperature therefore reducing the draught effect. The most energy efficient windows are generally double or triple glazed, mounted in an insulated unit. The space between the panes of glass is air tight and sometimes filled with gas to reduce the heat loss.
Specially treated energy efficient windows have a thin reflective metal film placed on the inside window pane. This allows less heat to pass through the window reducing the U-value of the window. When the sun shines the window allows solar heat to pass through into the room but then doesn’t allow that heat to escape. The cost for heating the property is reduced. When new windows are being chosen, the U-value should be 1.2 or less.
Installing EnergyBlinds solar blinds will reduce both the U-value and g-value of your windows – in turn reducing both your heating and cooling costs by up to 30%.
