Why do business windows get cleaned so often?

The National Glass Association's cleaning paper sets its trigger in the condition of the glass. Glass Technical Paper FB01-00 says: "For routine maintenance, interior and exterior glass surfaces should be thoroughly cleaned as dirt and residue appear." Its quick-reference guide repeats the point from both sides, "DO clean glass when dirt and residue appear" and "DO NOT allow dirt and residue to remain on glass for an extended period of time".

Set beside that trigger is a separate line addressed to the people who run buildings. The same paper encourages glazing contractors, general contractors, building management and owners "to adhere to a regular schedule of maintenance cleaning". The two lines do not compete. One says what calls for a cleaning; the other asks the people responsible for a building to keep maintenance cleaning on a regular schedule. The paper does not spell out how the two fit together, but a schedule is one way to keep up with a condition that cannot be predicted to the day.

NGA applies the same thinking before a building opens. Architectural glass, it writes, should be "properly cleaned and protected throughout the construction process using a program of regularly scheduled maintenance". That sentence is about the construction process; the regular schedule of maintenance cleaning is the paper's line for buildings in service.

What NGA says is at stake for the glass itself is set out at whether windows can be too dirty to clean. The trade words around this answer, from salt spray to common elements, are defined in the glossary of exterior cleaning terms.

NGA declines to set one frequency for all glass, and it says why: "Cleaning frequencies should be tailored to the individual characteristics inherent to the site conditions, as well as the severity of local environmental factors and atmospheric pollutants that vary from region to region."

That regional variation is where a coastal building sits. The paper does print one general interval, in a sentence that carries its own regional qualifier, and it still leaves a particular building's number to the site. That sentence is quoted whole, beside the other published lines, under how often coastal glass needs cleaning in Naples.

NGA does not list the local factors, but salt spray is one a Gulf coast building lives with. UF/IFAS Extension describes the mechanism plainly: "As waves crash on the shore, salt particles in the air and beach blow inland." No source measures how much of that reaches a particular pane, and whether glass on the water side of a building needs more attention is its own question, taken up at windows facing the Gulf.

Who arranges the work varies with the building as well. In a condominium, whether exterior glass counts among the common elements is settled by the declaration, and who cleans exterior windows in a condo is answered on its own page.

Having tailored the frequency to the site, the paper does not pick it for any particular building. It routes that decision: "Contact a professional window cleaner, such as members of the IWCA, to discuss recommended frequencies for your particular building." The International Window Cleaning Association appears there as NGA names it, as an example of where that conversation happens.

What a clean front does for the business inside it is a narrow claim, and what window cleaning does for a storefront sets out the little that is actually published. 239 Exteriors' own line for business glass stays modest: clean windows help your home or business present a more polished appearance, which is the service described under exterior window cleaning for homes and businesses.