A method of installing a modular comfort assembly within an occupant support includes the step of providing a modular comfort assembly including a heating element and at least one of a ventilation diffuser bag and a lumbar support system, the heating element, the diffuser bag, and the lumbar support system being modularly attachable to each other on sides thereof. The occupant support includes an outer cover, an internal foam bun, and a frame. The method further includes the step of mounting the modular comfort assembly onto a surface of the foam bun beneath the outer cover.