There’s an interesting asymmetry to cleaning facades in New York. Simply put: the past was a lot dirtier than the present, so the first cleaning of a masonry facade is by far the most difficult. Everyone used to burn coal for heating, and for generating electricity, and for powering ships, so the air was full of coal smoke and particulates; cars used to have much dirtier exhaust. The picture above shows a particularly smoggy day from 1953, and that type of filthy air is generally not generated locally any more.
I bring this up because it appears that the local laws designed to make building owners improve the energy efficiency of their properties are working. “NYC Buildings Complying With Emissions Law Faster Than Expected” is a great headline and the full article is almost as good.
