A pocketed spring assembly comprises a plurality of parallel strings of individually pocketed springs of different heights. Each string is joined to an adjacent string. Each string has first and second opposed plies of fabric and a plurality of pockets formed along a length of the string by transverse seams joining the plies. An upper end of each transverse seam is below the upper surface of the string so as to partially separate adjacent pockets within a string of springs when the spring is relaxed. The strings of springs have ventilation openings to increase airflow.