Regular window cleaning is proven to have a positive impact on your business. The brightness of a building and a clear view from office floors indicate a business that is intelligent and in good health. Besides a professional look, clean windows also add to customer confidence and value in a company.

To ensure a clean looking facade at all times, we advise our clients to think of fitting cleaning cycle for their building before choosing facade access solutions. In other words: how often and long does it take to get an entire building’s facade cleaned?

In the previous article of this 2-part series we’ve taken a look at the different options of window cleaning that are available. In this second part we will take a more in-depth look at how a cleaning cycle is calculated based on a specific project.

The cleaning cycle

First off, lets state that a pre-calculated cleaning cycle is always an estimate based on technical assumptions. Actual cleaning times can differ from the calculation due various circumstances.

The calculation of a cleaning cycle isn’t a standard procedure for many manufacturers of facade access equipment. It is either requested by the client on beforehand (for example, they can request a certain amount of cleaning cycles per year) or the cycle is calculated in a later design phase of the access solution to verify the amount of cleaning time.

A cleaning cycle is calculated based on a number of factors which vary per maintenance solution. For creating the calculated cycle below we assume a solution with one (permanent) roof car installed at the top level of the building.

Taken into practice

As mentioned, we start with investigating the drawings of the building and calculate the number of square meters (or square feet) of glass panels that need to be cleaned. For this particular project, we calculated approximately 40 500 m2 (435 938 ft2) of glass panels on a 350+ meter (1150+ feet) high skyscraper.

Now that we know the amount of glass we need to calculate for cleaning, it is time to take a look at the technical capacity of the BMU; what is the hoisting speed* of the unit and how long does it take to make a single drop? And more important, how does this time influence the time of work that window washers need to take into mind.

* Maximum speed of vertical movement of the platform or cradle.

The roof car

The average roof car cradle travels at a speed of 12 meters per minute (39 feet per minute) and needs to be anchored to a restraint system every 12 to 20 meters (approx. 39 to 66 feet) – depending on the standards that local authorities state. Bringing the total number of restraint levels for this specific project to 16 – taking into account that for every restraint level the users need to take a minute and a half to attach the gondola to the restraint anchor.

If we look at the technical information above and combine this with the height of this building we can conclude that it would take approximately 54 minutes for the gondola to make one full drop – one drop consists of a single travel movement from the top of the building to approximately ground level. This includes the amount of time that has to be taken to restraint the gondola and is without performing any form of work along the way.

Based on the height of the building and the glass surfaces of all facades combined, it is estimated that a total of 74 drops will be needed to cover the entire building. Making up for a total drop time of 7992 minutes (74 drops x 54 minutes x 2 for up and down).

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