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Are sash windows good for ventilation?

Are sash windows good for ventilation?
Are sash windows good for ventilation?
Fri Mar 4

Sash windows are opened by sliding both the top and the bottom panels downward and upwards respectively. Opening the window the same length at both ends is the perfect way to maximise airflow, cooling and refreshing the room naturally and efficiently, and in a much more efficient way than other window styles can achieve. This is because they have the best ventilation.

How does it work?

Simple physics tells us that warm air rises and cold air, which is heavier, falls. Cold air falls because it is more dense, meaning its particles are closer together, making it heavier per cubic meter. Heavy things experience a stronger gravity pull than lighter things, therefore when this cold air enters the room, it falls to the bottom of the space. This pushes the warmer, usually staler, air that’s already in the room upwards due to displacement.

Fresh, cold air comes through the bottom opening of the sash window, pushing the warm, stale air upwards and out of the top opening of the window. As the warmer air escapes, it allows even more cold air in through the bottom; this starts a continuous cycle, constantly renewing the air in the room and therefore keeping it fresh and cool.

Compared to casement windows

Timber casement windows usually only have one opening, which is side or top hinged. They can be opened wider than sash windows, but because there is only one opening, they just allow for one direction of airflow. Cold air can come in, but there is no convenient way for the warmer, staler air to move out and so it often lingers trapped at the top half of the room. This slows down ventilation, as it allows less cold air to enter the room.

Timber sash windows tend to be more expensive to fit and maintain than other window types, and there are other ways to improve ventilation, such as installing air-conditioning units. However, sash windows have no running costs, take up no extra space and are more environmentally friendly. They have no carbon emissions, unlike air-con units, and require no energy source or periodical upkeep.

Sash windows are the best for ventilation

Whether you are planning to install new windows or complete some sash window restoration, rest assured they are the best windows when it comes to natural ventilation. When used properly, they will help keep the air in your rooms fresh, and help keep them cooler in hotter weather. For more on sash window ventilation, be sure to check out our product range.


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