Paarhammer Windows & Doors lists out five key considerations for buyers when purchasing windows.

The five important components of a good window are glazing, frame material, seals, locking points and installation. Each component has a key role to play in the performance of the window, with all the elements coming together for the making of a good window.


Double glazing is a common design feature in modern windows; however, the width of the air gap between the two glass panes is an important factor. Anything from 12mm to 20mm is ideal as it is the air or gas between the two panes of glass that provides energy efficiency. Triple glazing should have two 12mm air gaps to increase the efficiency even more.


The ideal frame material should be a bad conductor so that the temperature on one side does not come through to the other side. Timber is a proven material as a bad conductor while aluminium is a good conductor that allows the heat or cold straight inside, resulting in condensation problems. Also consider the impact of the material on the environment in terms of its sustainability and energy consumption during production.


A draft around the window sashes results in a high air exchange that cannot be controlled, effectively negating the use of double glazing. The high air exchange also means that the new air has to be heated or cooled each time increasing energy consumption. 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 will completely eliminate drafts as well as noise.


Installation is an important element that impacts a window’s performance. The gap between the window frame and the wall should be properly sealed, preventing the creation of a weak link. Paarhammer uses expandable foam featuring excellent insulation properties.

Window manufacturers can get their window products rated by the Window Energy Rating Scheme (WERS), which rates the whole window including the frame, complete with seals and locking points, not just the glass unit. The lower the U-value of the window, the better its energy efficiency.