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About energy efficiency

Windows are a key element in reducing a building’s heating consumption to the lowest possible level. Considerations when purchasing windows and doors can be seen below:

Window orientation

The best window solution varies depending on which direction the window will face. For windows facing north it is important to focus on insulation, as from this direction there will be minimal solar gain. Windows facing east, west or south should be optimized to utilise the solar heat, focussing on the windows G-value.

Solar shading

Glass and window development has allowed manufacturers to create large spans of glazed areas. These large areas often require optimized glass to control the solar gain at certain times, especially the summer months.


A key aspect of a building’s windows and doors is the installation. The weakest area of a window or door will be around the frame so it is of great importance that the correct installation methods are used. Installation materials with the same insulation properties of the windows should be used to minimise the thermal bridge.

Glass to frame ratio

Windows and doors with a greater glass to frame ratio will allow a greater amount of solar heat into a building. Windows and doors with larger frame profiles but of the same overall size will allow a lower percentage of heat and light into the building.

Our energy solutions

Idealcombi’s energy window systems (Futura+, Futura+I & Nation Energy) offer low U values as standard and can achieve values of 0.80 w/m²k or lower when triple glazing is used.
To help us achieve high thermal performance, Idealcombi offers a range of standard energy solutions as well as optional extras:

  • Minimum standard of double glazed units with one pane of low energy glass and argon gas filling.
  • ‘Warm-edge’ spacer bar technology is used between glass panes as standard.
  • Triple glazed units incorporating two layers of low energy glass at an additional cost.
  • Krypton gas can also be used as an alternative to argon to improve U values further.
  • A wide range of enhanced solar control glasses to satisfy specific G Value requirements.
  • Our Futura+ range of windows and doors is manufactured using a polyurethane core as standard to minimise the effect of cold bridging.

Explanation of energy terms

Uw = rate of heat loss through the window

Gw = total solar heat gain through window

Eref = Energy balance of a standard window

LT = Light transmittance through window

about energy in windows