This paper presents an environmental life cycle assessment of a roof-integrated flexible solar cell laminate with tandem solar cells composed of amorphous silicon/nanocrystalline silicon (a-Si/nc-Si). The a-Si/nc-Si cells are considered to have 10% conversion efficiency. Their expected service life is 20 years. The production scale considered is 100 MWp per year. A comparison of the a-Si/nc-Si photovoltaic (PV) system with the roof-mounted multicrystalline silicon (multi-Si) PV system is also presented. For both PV systems, application in the Netherlands with an annual insolation of 1000 kWh/m2 is considered. We found that the overall damage scores of the a-Si/nc-Si PV system and the multi-Si PV system are 0.012 and 0.010 Ecopoints/kWh, respectively. For both PV systems, the impacts due to climate change, human toxicity, particulate matter formation, and fossil resources depletion together contribute to 96% of the overall damage scores. Each of both PV systems has a cumulative primary energy demand of 1.4 MJ/kWh. The cumulative primary energy demand of the a-Si/nc-Si PV system has an uncertainty of up to 41%. For the a-Si/nc-Si PV system, an energy payback time of 2.3 years is derived. The construction for roof integration, the silicon deposition, and etching are found to be the largest contributors to the primary energy demand of the a-Si/nc-Si PV system, whereas encapsulation and the construction for roof integration are the largest contributors to its impact on climate change. Copyright © 2012 John Wiley & Sons, Ltd.