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What makes a Window a Good Window

What makes a Window a Good Window

At recent home shows this question was asked often, so I will try and answer it here:

A good window consists of 5 parts:

glazing, frame material, seals, locking points and installation


Double glazing is now quite common but it is important to consider the width of the air gap between the glass. Anything from 12 to 20mm is ideal as it is the air or gas which is between the two panes of glass which provides energy efficiency. Triple glazing should have two 12mm air gaps to increase the efficiency even more.


Look for a material which is a bad conductor so the temperature on one side does not come through to the other side. Timber fits that bill perfectly while aluminium is such a good conductor that it brings the heat or cold straight inside and you end up with condensation problems. It is also worthwhile to consider the impact of the material on the environment: is it sustainable, how much energy is used to produce it, etc.


A draft around your sashes means a high air exchange which you cannot control, effectively negating the use of double glazing. In traditional situations it could be that all of the air in the room gets exchanged 18 times per day, just think of how much it will cost to heat or cool all of that new air each time. Good seals are imperative to energy efficient windows, and are best when used in addition to double rebates.

Locking points

Multiple locking points all around the frame in conjunction with good seals spells an end to drafty windows and put you in control of ventilation. They stop drafts as well as noise.


Another important point often overlooked is the actual installation of your windows. The gap between the window frame and the wall should be properly sealed, otherwise you are creating a weak link. We use an expandable foam which has excellent insulation properties.

Window manufacturers can get their products rated by the Window Energy Rating Scheme. WERS rates the whole window including the frame – seals and locking points are part of that – not just the glass unit itself. The lower the U-value the better the energy efficiency of the window. Also check the figures for air infiltration as the lower these are the less draft you will experience. This is especially important also for sliding doors which have had the reputation to be notoriously drafty.

If you have any further questions about how to make a window a good window please contact us and we will post your question and the answer so other people might follow the conversation. If you prefer to talk to us direct please call us on 03 5368 1999.

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