Agree about the sky, moody , broody clouds would suite this a treat.
Next time, try exposing for the sky (and bracket your exposures), it's easier to pull back midtones and shadows (of the building) than put back detail that's not there (sky)
Canon 1DS MKIII,7D, 85 1.2L, 24 F1.4L, 135 F2L, 200mm F2.8L,50mm F1.4, 120-300 F2.8, 12-24mm f 4.5
http://www.lesmclean.co.uk/
Concentrate on equipment and you'll take technically good photographs. Concentrate on seeing the light's magic colours and your images will stir the soul. - Jack Dykinga