Increasing the amount of urban vegetation is encouraged as an adaptation strategy to countermeasure climate change mainly due to (1) its potential to sequester CO 2 from the atmosphere and to (2) enhance evaporative cooling and positively influence the water cycle in cities. The greening of buildings, that is the implementation of vegetated envelopes on roofs and walls, may contribute to an important part of the urban green infrastructure. However, the carbon sequestration potential of green building envelopes is one of the ecosystem services that has the least been studied due to complexity or lack of data. GREENVELOPES aims at filling this research gap by conducting an in-depth observation and process-based modelling study of building green enve- lopes to better understand their capacity to exchange carbon and water with the urban atmosphere. The research objectives will be addressed by state-of-the-art observations of micrometeorological fluxes and leaf-level measurements at a green roof and green wall site, covering different weather conditions during a two-year period. This is to be complemented by improving an established urban energy balance model so that it accounts for carbon and water exchanges of building green envelopes with the urban atmosphere. Upscaling these exchange processes to the urban scale by the numerical modelling of two application cities, Toulouse (France) and Berlin (Germany), will allow us to quantify and assess the impact of both types of green envelopes on carbon sequestration and evaporative cooling potential in relation to other types of urban vegetation.