Toward net-zero energy buildings in hot-arid climates: a systematic review of energy efficiency and renewable energy integration in the Iraqi residential sector

Residential building energy efficiency plays a crucial role in curbing electricity demand in hot-arid climates where cooling represents a major share of household electricity consumption. Residential buildings are a fast-growing electricity demand sector in Iraq, but the potential of energy efficiency measures (EEMs) and renewable energy technologies (RETs) has not been comprehensively assessed. This study presents a PRISMA-based systematic review of 55 selected studies published between 2014 and mid-2025 to highlight strategies, performance indicators, and challenges in implementing EEMs and RETs in Iraqi residential buildings. The findings reveal that building-envelope measures are the most significant factor on the demand side, with integrated envelope measures delivering energy reductions that vary depending on the intervention context, reaching around 50% under more comprehensive retrofit-oriented scenarios. On the supply side, renewable energy technologies (RETs) − especially rooftop photovoltaic (PV) systems − demonstrate promising potential, with appropriately configured and sized systems able to meet a significant fraction of household electricity loads under Iraqi climate conditions. While EEMs-RETs integrated approaches are limited, optimized NZEB-oriented scenarios combining comprehensive energy-efficiency improvements with on-site renewable energy technologies demonstrated substantial reductions in reliance on grid electricity. Despite such opportunities, the literature is primarily simulation-focused with limited field validation and integrated techno-economic and policy analyses. As such, this study presents a NZEB-oriented integrated framework coupled with an implementation-oriented approach combining retrofit depth, demand reduction, renewable integration, economic considerations, and implementation challenges to support the transition toward energy-efficient residential buildings in Iraq and other hot-arid climates.