This study investigates the life cycle environmental performance of a large office building (11,400 m²) in Tehran’s semi arid climate towards NZEB. A sequential simulation framework is developed: DesignBuilder for passive optimization (EPS insulation, PCM, multi layer green roof) and HOMER Pro for a 273 kWp grid connected PV system without battery storage. A cradle to grave LCA (One Click LCA, EN 15978) and circularity assessment are performed over a 60 year service life. The best passive configuration reduces total energy demand by 11.8%. Adding PV cuts annual grid electricity purchase by 65.5% (from 271.1 to 171.2 MWh), making the building a net electricity exporter (110.6% annual penetration). Although the active scenario increases embodied carbon by 16% (from 6,887 to 7,990 t CO₂e), it lowers operational carbon by 58.7% (from 30,871 to 12,755 t CO₂e), resulting in a 44.7% lower total life cycle GWP (20,902 vs. 37,758 t CO₂e). The carbon payback of the full passive active package is only 5 years. A negative trade off for PCM is observed (+154 t total carbon vs. EPS only), and circularity improves from 11.5% to 13% material return to cycle. The proposed battery less passive active framework demonstrates a fast repaying, low carbon NZEB pathway suitable for developing countries with unstable grids. The findings also caution against using PCM in climates where EPS already provides effective insulation.