Windows -> Energy Savings

Highest heat loss through a home is via windows. Heat loss is either by radiation, conduction through glass, or by convection through the movement of air gap between two glass plates. Radiation factor is the most important one which has been taken care of with the latest improvements.

• Low E coatings make sure most of the heat stays inside the home. The coating comes in two versions, soft coat which has a lower emissivity (Better performance) and hard coating.
• Low E coatings are applied to either the glass directly, or on plastic films. Rule of thumb: Thin ones suitable for where maximum sunlight penetration is favourable. Of course a thicker one provides better cooling. 
• Reducing the conduction between two sheets of glass is the task of argon gas.
• The hardware used as spacers in a window as well as the window frames are made with low conduction material. Framing material are fibreglass, vinyl, wood, and aluminum.
• Weather stripping blocks heat exchange.
• Installing a window frame properly ensures absolutely minimum energy loss. Trade person in charge of overall home construction knows the method of  installation based on the type of air barrier system used.
• Look for Power Smart label on windows.
• The specified R value is measured at the centre of the window. Since windows are exposed to sun rays, their efficiency fluctuates based on how hot or cold they are. Another unit that considers these factors are called ER (Energy Rating). The larger the ER the higher the performance. 
• Window frames are the weak link in overall design. For this reason, a single large window is better than several smaller ones (covering the same area).
• One last point regarding frame material. While PVC (Vinyl) and fibreglass are the best energy savers, however aluminum frame are more durable.  Wood frames are attractive, and require maintenance.

In cold climates, the more sun shining through, the more pleasant it would be. More windows make the house not only a lively place to spend time in, it also eliminates odours and some people believe in its healing power. The other side of the story reveals that more Windows equals more heating bill.

By: Jay Kajavi – March 7, 2011