For the IGF project 20540, a flexible "textile" heat exchanger element was developed for use in systems for decentralized domestic ventilation.

The approach pursued was to produce a double-loop structure from metallic yarns separated by a flexible textile. For textile production, a tufting machine was modified in such a way that the dead pile, which normally lies flat on the carrier, is raised and thus also forms loops. A spunbonded nonwoven fabric with a hotmelt film was used as the tufting backing. After tufting, the hotmelt adhesive was melted to bond the yarns to the carrier and improve the airtightness of the spunbonded nonwoven.

The yarns used were stainless steel fiber yarns and copper strands.