How often should you clean your windows?

The starting point: twice a year

For an ordinary home, spring and autumn is a sensible rhythm. Spring takes off the winter's salt, soot and rain spatter; autumn takes the pollen and summer dust before the dark months, when every streak shows against lamplight. This is Avavik's experience of what people actually book – there is no standard or official recommendation to follow.

What makes it needed more often

• Traffic and city air. Windows facing a through road go grey in weeks, not months. Exhaust particles and brake dust settle as a film you don't see until the light hits at an angle.
• Which way they face. South-facing windows show everything: the sun shines straight through every streak. North-facing ones look clean for far longer.
• Near the sea. Salt on the glass is its own problem – less visible, but it dulls the surface over time.
• Trees and greenery close to the house. Pollen, sap from deciduous trees and bird marks make for short intervals in spring and summer.
• Pets and small children. Nose marks and handprints on the lower half of the pane are the most common reason for an extra visit between planned ones.
• Building work nearby. Construction dust is fine and persistent and settles into the surface of the glass.

What makes less often fine

A flat high up with a glazed balcony, windows in shade, little traffic and no pets: once a year can be perfectly reasonable. What decides it isn't the calendar but whether you can see the dirt.

A simple test

Stand at an angle to the window with the light behind it, rather than square on. Dirt on glass is almost only visible when the light runs along the pane. If you see a film, a streak or a cloudy patch, it's time – whatever the calendar says. If you see nothing against the light, the window is clean, however long it has been.

Practical notes if you book

Two things affect the price more than the number of windows: whether the panes can be reached from inside, and whether the windows are coupled – two panes that open and need cleaning on four faces instead of two. Count your windows, note which sit high or don't open, and put that in the enquiry. Then the price you are quoted is the price that holds.

See companies and prices for window cleaning, and read about what a window cleaning includes and about high windows.