New crawl space fiberglass insulation - Strong odor
Your comment about &quot;burnt cotton candy&quot; triggered my memory of this article that I read a while ago.  From Green Building Adviser on smelly eco-friendly fiberglass.
The article describes the glue used as having a sweet burnt smell:

According to Frank O’Brien-Bernini, an Owens Corning vice president
and chief sustainability officer, “The new binder was introduced a
couple of years ago. We have totally converted our entire product line
to this product.”
O’Brien-Bernini admits that you can smell the binder
when you open a fresh bag of insulation. He reminded me that
old-fashioned formaldehyde-based glues also have an odor — one that is
sometimes compared to cat urine. “Our prior insulation also had an
odor to it that was far less pleasant,” O’Brien-Bernini said. “When we
started developing this product, we did an aroma test. Most people
said the new aroma is far preferable to the aroma of the prior
product.”