The act of comparing double glazed sash windows to single glazed windows is fairly simple. Sash windows, originally single glazed, are now made in double and even triple glazed models for greater energy efficiency. This extra glazing does not have to compromise the appearance of the window, which may be important to the integrity of an historical restoration or to the design of a modern house.

The earlier type of casement windows, which hinged on the sides and were opened by being pushed outwards, were the main type of window until the mid 1600s, when sash windows were invented in England. These windows consist of two or more panels, with at least one which can be raised and lowered to open the interior to outside air and close it out again.

The term glazing actually refers to the glass used in windows – or to be precise, a transparent sheet of material in a window frame. Some windows are now glazed with clear plastic. Replacing window panes, sometimes called glazing, is really reglazing. A single pane of glass used in a window may be replaced by two panes with an air space in between, for added insulation against sunlight, outside temperature, and noise. Modern windows are often double glazed to start with, of course.

If the windows of your home are single glazed, you will reduce your consumption of energy by changing them over to double glazing. The increased efficiency will probably entitle you to tax credits from the government, which covers part of the cost of window replacement in this way. Many countries are hoping to help homeowners use less energy with such incentives.

Using other methods of insulating windows usually is less satisfactory. A clear film insulation may be applied to the glass, or the glass may be tinted to block sunlight. However, the increase in energy savings will not compare to those realized by window replacement or even installing double panes in old windows, which an expert glazier can do. In this way, the integrity of an historic structure can be maintained while energy use is reduced.

There are many sites on the Internet with advice on the best way to install double glazing, either with new glass in old windows or by replacing the entire window unit. It is easy to compare products and prices, and to decide whether to attempt this yourself or to hire it done by professional contractors.

Comparing double glazed sash windows to single glazed windows will show that the double paned windows are far more energy efficient. The appearance of an older house or building can be preserved if windows are updated. It is a good idea to construct modern homes with double glazed windows to start with.

The utilization of double glazed sash windows helps to keep energy usage at a lower level than you would obtain with single glazing. Sash windows are historically a great method to promote natural energy efficiency.