What about those windows?

According to the National Insulation Association windows and doors typically account for 20% of all heat loss in a home. A leaky single glazed window will also have a big impact on comfort, given the draughts, not to mention the cool temperatures adjacent to the window. This is frequently borne out in our energy surveys; barely a report goes out that fails to make some recommendation to improve windows

The means of heat loss from windows is more complex than one might assume. But there are two characteristics which largely determine how well or poorly a window conserves heat; the U values of the glazing and timber and the degree of air tightness of the window. The latter can be particularly decisive with period sliding sash windows. Research undertaken by English Heritage found that 60% of overall heat loss could be attributed to air leakage.

So in very plain terms there are two objectives, improving the insulation values of the window and reducing any uncontrolled air movement. But what is the best way of meeting these goals? There are a good many options available which vary significantly in effectiveness and cost. Do you refurbish or replace?

Air Tightness

Insulate

Very crudely speaking, air tightness can be significantly improved without having to replace a window. However if you’re looking to make inroads into the heat loss through the glazing you should really be considering replacement windows. Incremental improvements can be achieved with the use of curtains, shutters and blinds. On the other hand there would be little point in installing Passivhaus standard triple glazed windows if the other elements of the building are a much poorer thermal standard. It also seems pretty wasteful to replace windows that are in a good shape. Of course the most natural time to upgrade your windows is when they need replacing anyway. But maybe that’s too long to be cold.

Deciding what to do with your windows is not clear cut, there will undoubtedly be a number of things you’ll need to factor in. Just make sure you know what all the options are. And make sure you choose a tradesman you can trust; otherwise missed delivery times will only be the start of your worries!

 

Inigo Harrison