The comfort within residential buildings is closely linked to indoor climate conditions, which rely on adequate air quality achieved through ventilation rates exceeding minimum standards. Typically, window ventilation leads to significant energy loss. Modern building ventilation systems present a sustainable alternative by utilizing energy recovery devices. Air-to-air heat exchangers facilitate contact between discharged and fresh air through impermeable plates, recovering only sensible heat. By replacing these plates with water vapor permeable membranes, latent heat recovery becomes possible, resulting in membrane-based enthalpy exchangers. Efficiency depends on fluid dynamics, material properties, and process parameters. This thesis explores these governing factors, identifies transport limitations, and suggests solutions. The influence of vapor activity on membrane permeance was assessed across various materials, revealing that permeance is highly dependent on feed and permeate activity. Mixed-gas measurements detailed the overall transport resistance, highlighting the consistent impact of boundary layers. Performance losses from stagnant layers were reduced using membrane spacers. Additionally, modeling heat and mass transfer in membrane-based exchangers helped identify economic limits for material optimization. A case study indicated that the effectiveness of membrane spacers varies with external climate, energy costs, an
