The purpose of this work was the investigation of the influence of the microclimate on the ageing behavior of polymeric encapsulants for photovoltaic (PV) modules. Different types of encapsulation films were investigated. Single film and laminated samples were artificially aged under different conditions (with and without irradiation). The results showed that there is a strong influence of the microclimate on the aging behavior of polymeric encapsulant materials on the optical, chemical and morphological properties of the materials. Differences were even detectable in the unaged state between film and module samples after the production process. Not only has the sample set-up (film or laminated module sample) highly influenced the degradation of the encapsulants, but also the type of aging (dark aging or aging with irradiation).