Insulation cockloft (flat roof) - efficient + green possible?
Any suggestions for efficient and effective but non-toxic and reasonably priced insulation for the area between a brownstone's top floor and the flat roof? I've been researching it and it seems there was some dialogue about cotton batt (recycled denim) a number of years ago, and then there is the question whether wet or dry cellulose is appropriate under a flat roof both in terms of risk of mold and losing its insulating properties if wet cellulose doesn't dry properly before being sealed up, or if dry cellulose gets wet (if that is right) not to mention that it seems cellulose is much pricier than fiberglass insulation. I'd be interested to know what others have done. This is for a 100+ year old brownstone in New York City.