An article of apparel may include a polymer chamber element that defines an interior void for containing a substance in either a liquid or a solid state. Depending upon the substance located within the chamber element, the apparel may be utilized for increasing or decreasing the body temperature of the individual. The chamber element may have a plurality of subchambers, which may have a triangular shape and may be in fluid communication. In some configurations, the subchambers may have different sizes or volumes.
