This question isn’t as straightforward to answer as you might think. It depends on two key factors: location of the business, and type of business.
Let’s expand on this.
Location of business
If your business is located in a large city like London where pollution levels are high and there is dirt and dust in the immediate atmosphere due to construction or road work taking place nearby, then you can expect to have to clean the office windows more frequently. Likewise, if your office sits near a busy road where traffic volumes are high, over time, a build-up of traffic film will make the windows look dirty. Alternatively, if you are based in a village or a quieter location in a town, then your windows shouldn’t need to be cleaned as often.
All parts of the UK see a significant amount of rainfall in a year, but some areas see more rain than others. In areas of higher rainfall, office windows may need to be cleaned more regularly due to the mineral deposits in rainwater, which can leave smudge and stain marks on windows.
Type of business
Shops and retail outlets, restaurants, cafes, and high street premises which showcase information in their windows for passersby to look at, such as estate agencies, should all clean their windows more regularly, and in many cases, twice a month is necessary. In any establishment when food is being prepared, cooked and eaten, such as restaurants, there will be more of a build-up of grease in the atmosphere, making the interior windows appear grimy quite quickly.
Healthcare institutions, hospitals and medical practices should keep their windows well-cleaned both inside and out, and might need to be cleaned as regularly as once a month.
For most general office buildings, cleaning the windows twice a year is usually ample. However, ground floor windows and any glass-fronted entrance doors may require cleaning more frequently as this is what visitors and potential clients will see when they visit your premises.
Facilities Managers should do their best to monitor the windows of their office building. If the windows are cleaned twice a year and it seems ample, then that is fine. But there are always exceptions. For example, the site next door to yours might be a site where new building work is taking place, and construction lorries and workers are constantly arriving at and leaving the site. Not only will there be more traffic activity, but building work always creates a lot of dust which will land on the windows. During the months when this work is taking place, you may find you need to arrange for the windows to be cleaned more often than usual.