The pros and cons of low-E glass

One area in the home that you should pay special attention to are the windows as this is where a lot of heat can be lost. There are several ways to reduce heat loss through the windows, one is installing double glazed windows and the other is to use low emissivity or low-E glass. Here are some pros and cons of using this material.

Why choose an energy saving glass

Double-glazed windows vary in efficiency according to their construction, and perhaps more importantly, through the gas that is used within the gap. This means that it is always a good idea to choose the best quality of windows that you can afford. In addition, you should always ensure that they comply with the Building Regulations and the minimum required energy rating or U-value (see below). The gap between the panes should be a minimum of 16mm, and the glass should ideally be 'low emissivity', which will ensure that heat will be kept in when it is cold outside and, conversely, that heat will be kept out during periods of hot weather.

Low emissivity glass

All new double or triple glazing panels, as well as any supplied in new or replacement windows, should be given a low emissivity coating. Advantages The advantage of using low-E windows is fairly straightforward. First, the low-E coating will greatly reduce heat loss through the windows. In fact, the reduction in energy loss here could be as much as 30-50 percent. Second, while most double glazing just has a low-E coating on the cavity side of the inner pane. You can greatly improve its performance in energy reduction by specifying it on both panes within each double glazed unit. Disadvantages The only real disadvantage of using low-E windows will be, of course, the initial outlay. This type of glass may cost up to 10 or 15 percent more than uncoated glass. However, due to the reduction in energy bills when using low-E glass, this initial outlay will be recuperated in a relatively short time.

Window energy rating

All new replacement windows must have a window energy rating of 'C' or above, or must have a whole window 'U' value (rate of heat loss through a structure) of
1.6 W/m2K. If you are replacing windows, you'll need to go through the Local Authority Building Control process, or have the work done by a company registered with the Fenestration Self-Assessment (FENSA - Fensa.org.uk) which will certify that the installation work complies with the current Building Regulations.