The present study was to investigate the effect of green roofs on carbon (C) footprint and compare carbon dioxide (CO2) emission and sequestration of such roofs during their lifetime in the city of Mashhad, Iran. Considering the climate of the area of interest, six cold- and drought-tolerant plant species, including Sedum acre, Hylotelephium spectabile ‘Boreau’ (syn. Sedum spectabile ‘Boreau’), Crassula capitella, Frankenia laevis, Vinca major, and Rosmarinus officinalis were chosen for this purpose. CO2 sequestration of these plants under certain light intensities in the range of 400–2600 μmol/m2.s was then measured by an infrared gas analyzer (IRGA). Carbon dioxide sequestration under all light intensities in the area of interest for a 40-year period from 1979 to 2019 was estimated with the help of Matlab software. Afterward, CO2, emitted during green roof construction, was estimated through the simulation of a four-story building, with a floor area of 180-m2, in the Design-Builder software (v.6). As well, CO2 emission induced by roof maintenance activities was predicted based on cost estimates, obtained from an economic analysis of maintenance activities. The study results showed that a roof covered with Frankenia lae- vis was estimated to sequester 68.7 kg/m2 of CO2 over a 40-year period while emitting 22.65 kg/m2 of CO2 during the same time. Under high (> 1500 μmol/m2.s) and low light intensities (< 1300 μmol/m2.s), Sedum acre and Rosmarinus officinalis also demonstrated the best performance in terms of CO2 sequestration.

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