Windows & Doors

Energy-efficient windows will:

Increase your comfort, Energy-efficient windows reduce cold drafts and make a house feel warmer during the heating season.
Help control condensation, the interior surfaces of energy-efficient windows stay warmer, which means you can maintain a higher level of relative humidity without worrying about condensation on the windows (keep in mind that efficiency improvements to windows will not prevent condensation if the humidity level in your house is too high).
Save you money, by minimizing air leakage and improving the thermal performance of your windows, by adding interior storm windows, for example, could improve their energy efficiency by up to 50 percent and reduce your energy bills.

Polyethylene or Rigid Plastic Storm Windows

Installing plastic sheeting over the window is an inexpensive and easy way to improve the heat retention of your home and reduce condensation. The plastic will be less durable than glass and will have to be re-installed each year if the windows are opened. There is an inexpensive kit on the market that has a plastic sheet that is heat-shrunk in place using a hair dryer. This system is best for windows in seldom-used rooms and basements.

Frames

Wood, PVC, aluminum, fibreglass and composite frames are available and each type varies in strength, longevity, air leakage and insulation value. In a conventional double-glazed window, the insulation value of a solid wood frame or good quality vinyl frame is about the same as the glazing - R-2. Aluminum frames, even those with thermal breaks, are often less efficient. Generally, a well-designed PVC or fibreglass frame has slightly greater insulation value than wood, particularly if hollows in the frame are filled with insulation. However, a poorly designed, metal-reinforced PVC frame may not perform as well as wood owing to thermal bridges or greater air leakage at low temperatures. A frame can occupy up to 30 percent of a window's area, reducing the window's potential for solar heat gain. Narrower frames with higher insulation values are therefore desirable. Fibreglass frames offer insulation and strength in a low profile frame contributing to some of the highest energy ratings.

Gas fills

Low-E coatings can reduce radiation heat transfer to the point that transfer owing to natural convection becomes dominant. However, this convection loss can also be reduced substantially by filling the air spaces between panes with an inert, high-molecular weight gas like argon or krypton. Research indicates that careful sealing limits gas loss to less than 2% annually. A window's gas fill could therefore remain effective over its expected 20-year life. High performance windows admit the sun's warmth while significantly reducing both house heat loss and air leakage. Houses built to recent code requirements have generally been constructed with conventional sealed double-glazed windows. With an R-value generally equal to only one-tenth of the house walls. But today's high performance windows capture more heat from the sun than they allow to escape to the outside. The new technologies which make this possible include:

Low- emissivity (low-E) coating on the inside glazing surface to reduce radiant heat loss new glazing materials
An insulating, inert gas between panes to reduce convection heat loss
Insulating spacers separating panes, to reduce conduction heat loss and condensation along edges
Better sealing in the frame components to prevent air leakage
Frames that lose less heat and are narrower to admit more solar energy
Greater durability through design and careful use of materials
Improved installation practices to minimize air leakage around the window