What location in the troposphere would the risk of potential danger of the balloon leaking be the most acute?

Question

At extremely low temperatures, thin polyethylene fabric would become brittle. Any small flaws in the fabric could cause a balloon made of the fabric to spring a leak and break. Which location, upper, middle, or lower, in the troposphere would the danger be most acute?

Answer 1

Are you referring to a "hot air" balloon or a gas filled balloon (like from a balloon vendor)?  

Hot air balloons are usually made of nylon (not polyethylene) and work on the principle of heated air rising.  This material does not break, it can tear, so it does not really fit your question.

Gas filled balloons can be made of polyethylene but are usually made of a latex compound.  Latex expands as the balloon goes higher due to the differing air pressure inside and outside the balloon. Polyethylene is only marginally plastic (stretchy) so it will tear/rupture rather than burst if it is punctured.

Regardless of balloon type, the higher up you go, the greater the danger - higher has lower relative air pressure, colder air temperature and stronger winds.

You would probably get a better (more educated) answer if you posted this question in the "Weather" section of Y/A.