With energy modeling tools now available to architects combined with the latest in window technology new homes for cold climates can now be designed to significantly reduce the energy needed to heat the home by leveraging freely available solar heat gains. In essence, while the sun is out windows can heat your home even when temperatures are well below zero.
The most advanced windows are being manufactured in Europe with some manufactures in Canada coming close in performance. These advanced windows combine an insulated frame, glazing that allows a high percentage of solar heat to enter the home - high Solar Heat Gain Coefficient (SHGC), and air tightness.
Single panes of clear glass allow around 85% of solar heat to pass through. However the early single pane windows were little better than a hole in the wall in preventing heat from escaping from the interior of the house. As factory production became more sophisticated and glass coating technologies were invented the capacity of windows to prevent heat from escaping was greatly improved. Sacrificed in this development though was the glass’ ability to allow solar heat to pass through reducing the SHGC to around 30%. This is still true for the majority of domestically manufactured windows.
Roughly speaking the European manufactured windows from countries like Germany, Switzerland, and Austria have twice the insulation value, allow twice the amount of solar heat gain, and maintain more air tight seals. All these qualities are particularly important for energy efficient buildings in cold climates. Installing the latest in window technology in new construction in cold climates should be considered a conservation measure and given higher priority over adding renewable energy systems.