Design

How can the type of glass I choose improve the energy efficiency of my home?

You may be surprised that, even when closed, windows are one of the main paths by which energy enters and leaves your home. Glass is particularly important in this.

With our selection of glass, we are trying to balance three main factors:

• Capturing natural daylight
• Keeping cool in summer
• Keeping warm in winter

The use of performance glass can make a significant contribution to all of these. There are two main measures that are used to describe the performance of glass, solar heat gain coefficient (SHGC) and thermal conductivity (U Value).

For a hands-on experience, look out for an Interactive Demonstration Unit at a window supplier near you or view the movie below for a demonstration.

 

Solar Heat Gain

Solar heat gain is the heat you experience when sunlight passes through a window and heats the surfaces and air inside a home. This heat is a bonus in winter, when it can save on heating, but definitely not an advantage in summer.

Both the orientation and the windows themselves affect solar heat gain in homes — therefore it’s a very important consideration in the design of a comfortable home. Certain glass types are designed to reduce the amount of solar heat gain passing through the glass (Low SHGC). Toned glass is an established approach to reduce SHGC. The addition of Low E glass can improve this performance even further.

At a Glance

• Solar heat is generated when sunlight passes through a window and heats the surfaces and air inside a home.
• Depending where you live, solar heat gain will generally be desirable during winter, but not in summer.
• In warmer climates, controlling solar heat with modern performance glazing can reduce air conditioner use significantly.
• Today’s glass technology offers outstanding solar heat control options for all climates.

Glass Insight

Direct sunlight on a square metre of ordinary glass during summer has the equivalent heat output of a single bar radiator.

Thermal Conductivity – the Flow of Heat Through Glass

The greater the difference between the outside and inside temperature, the greater the heat flow, especially through windows using ordinary single glazing. In cool weather, valuable heat is lost to the outside, so your heating system will use more energy to keep your home at a comfortable temperature. Equally, in hot conditions, air cooling systems need to be larger and work harder to combat undesired heat flowing into your home.

Fortunately there are two readily available glazing technologies that dramatically improve the insulation performance of the window and improve its energy efficiency performance. Low E glass and Insulating Glass Units (IGUs), commonly referred to as double glazing, can be used individually, or combined to provide outstanding home insulation performance.

See How Performance Glass Works

 

 

Low E coated glass – thermal imaging demonstration

These images show the same view through a standard camera and one using a thermal imaging camera to illustrate the performance of a window with ordinary clear laminated glass and a window fitted with Viridian SmartGlass Low E glass.

Image 1 shows the view from inside the home, while image 2 shows the same home viewed from outside.

Image 1 – View from inside

Look at the thermal image on the right. See how half of the heater is reflected in the ordinary clear laminated glass and the other on Viridian SmartGlass Low E glass. The reflection is much more intense from the Low E glass. Compare this to the standard camera image on the left where the two types of glass appear similar.

Image 2 – View from Outside

As you can see in this thermal image the Viridian SmartGlass Low E glass is reflecting more of the heat inside and is letting less of the energy to escape through the glass. As a consequence there is far less energy escaping through the Low E glass to the outside.