Passive Architectural Design Parameters for Indoor Thermal Performance in Tropical Savannah, Nigeria: A Review of Residential Buildings

Residential cooling is among the fastest-growing energy burdens in Nigeria, where households account for a dominant share of national electricity demand and where grid supply remains intermittent. The tropical savannah (Köppen Aw) belt that spans the country's Middle Belt presents a distinct thermal challenge: a hot, low-humidity dry season with a large diurnal temperature range, followed by a warm, humid wet season with suppressed night-time cooling. Passive architectural design offers a low-cost, grid-independent route to indoor thermal comfort, yet the evidence base is fragmented and skewed towards the hot-humid south and the semi-arid far north, leaving the savannah residential sector comparatively under-theorised. This paper presents a systematic review, conducted in line with the PRISMA 2020 protocol, of 66 studies retrieved from Scopus and Google Scholar and screened for relevance to passive design, residential buildings and tropical-savannah conditions. The synthesis is organised around eight parameter families and yields three contributions. First, it proposes an evidence-weighted sensitivity hierarchy in which the roof, ventilation and external shading dominate the achievable comfort gains per unit cost. Second, it isolates a savannah-specific seasonal-duality problem, in which thermal-mass strategies that suit the dry season can become counterproductive during humid wet-season nights, and argues that adaptive or hybrid envelopes outperform single-strategy solutions. Third, it documents a persistent evidence-to-practice gap and converts the findings into a staged decision framework and a tiered set of guidelines for architects and policymakers. The review concludes that savannah residential comfort is achievable largely through fabric and ventilation measures, but only if design priorities are sequenced and codes are enforced.