Engineering Optimization of Natural Ventilation for Thermal Comfort and Energy Efficiency in Institutional Office Buildings in Hot-Humid Ede, Nigeria: A Field Evidence-Based Four-Stage Framework

Code This preprint presents field evidence-based engineering optimization of natural ventilation for thermal comfort and energy efficiency in institutional office buildings in hot-humid Ede, Nigeria (7°44'12"N, 4°26'10"E, 269m, Tropical rainforest Af climate). CONTEXT AND FUNDING:This research was funded by Tertiary Education Trust Fund (TETFund), Abuja, Nigeria under Institution Based Research (IBR) Grant Reference No. FPE/DRD/IBR/17-21/B6/2025/10 at Federal Polytechnic, Ede, Osun State, Nigeria. Tenure: January 2025 - October 2026. This preprint is submitted to Journal of Building Engineering (Elsevier, Q1, Impact Factor 8.1, ISSN 2352-7102) under review (Manuscript ID JBE-XXXX). It is distinct from concurrent Journal of Building Physics (SAGE, Q3, IF 2.3) submission focusing on performance and diurnal collapse per COPE guidelines - this paper focuses on engineering optimization and energy efficiency. METHODOLOGY:Triangulated approach: (i) 10-year climatic analysis (2013-2023) from Nigeria Meteorological Agency (NIMET) and Osun State Ministry of Environment, (ii) indoor environmental monitoring of 34 institutional offices per ASHRAE 55-2020 and ISO 7726 standards (air temperature Ta via Testo 176 H1 ±0.2°C, relative humidity RH ±2%, air velocity Vi via Testo 405i hot-wire ±0.01 m/s at 1.1m height, mean radiant temperature MRT via black globe Ø150mm, CO2 via Testo 315-3 ±3%, thrice daily 09:00/13:00/16:00 WAT for 14 days hot season 15-28 March 2024), (iii) morphological survey (Window-to-Wall Ratio WWR, depth, orientation, window type, obstruction 30%), (iv) occupant comfort survey n=182 using ASHRAE 7-point thermal sensation vote TSV scale (-3 to +3), thermal preference, acceptability (metabolic 1.2 met, clothing 0.71 clo tropical office), and (v) bioclimatic analysis using Givoni psychrometric chart (1992) and Mahoney Tables (1971), PMV-PPD via CBE Thermal Comfort Tool. Statistical analysis: Pearson correlation, t-test, SPSS v26, p<0.05. Ethics: FPE/REC/2026/04/182 applied for at Federal Polytechnic Ede Research Ethics Committee, formal letter yet to be issued - undertaking to provide, informed consent from 182 occupants. KEY FINDINGS:Baseline engineering failure: Indoor air velocity Vi mean 0.09±0.07 m/s (range 0.02-0.28) far below 0.8 m/s required for physiological cooling in hot-humid (Szokolay 2014, ASHRAE 55) - 89% deficit, operative temperature Top mean 32.5±1.5°C (29.8-35.2) exceeding adaptive comfort upper limit 29.5°C per ASHRAE 55 80% acceptability, indoor-outdoor Vi ratio 0.06 vs >0.3 recommended, Givoni comfort only 8.8% of annual hours vs 34.6% potential with Vi 1.0 m/s and 42.1% with Vi 1.5 m/s - 25.8% lost opportunity. Morphological barriers: building depth mean 7.1±1.8m (4.2-9.8) exceeding 5.5m limit for cross-ventilation and 2.5x floor height rule (76.5% offices >5.5m), WWR mean 18.5±6.2% (8-32%) - 68% offices WWR <20% well below 40-50% recommended by Mahoney Tables, single-sided ventilation dominance 46.2% (n=16) vs cross-ventilation 23.1% (n=8), single-sided with atrium/courtyard 30.7% (n=10), 30% windows obstructed reducing effective openable area by 25-40%. Occupant thermal comfort: TSV mean +1.4±0.9 (slightly warm to warm), only 18% neutral, 32% slightly warm +1, 34% warm +2, 12% hot +3, 82% prefer cooler, 58% unacceptable exceeding 20% PPD limit, PMV mean +1.6±0.5 (range +1.2 to +2.1), PPD 35-78% mean 58%, PMV overestimates warmth by 0.2 scale vs TSV supporting adaptive comfort theory. Strong engineering correlations: depth vs TSV r=0.54 (p<0.001), WWR vs TSV r=-0.48, Vi vs TSV r=-0.62, Top vs TSV r=0.68, WWR vs Vi r=0.56 (p<0.001). Cross-ventilation offices Vi mean 0.18 m/s vs single-sided 0.06 m/s (t=4.82, p<0.001), Top 31.2°C vs 33.1°C (t=-3.21, p=0.003). FOUR-STAGE ENGINEERING OPTIMIZATION FRAMEWORK:Stage 1 Orientation Optimization (long facade N-S, E-W walls minimized, 1.2m horizontal overhangs South, vertical fins East-West, building spacing ≥1.5x height for wind access) target -35% solar heat gain; Stage 2 Window Design Optimization (WWR 40-50% North-South walls, cross-ventilation mandatory with inlet windward Southwest and outlet leeward Northeast, unobstructed louvered windows effective openable 80%, sill 0.9-1.1m, head to ceiling) target Vi ≥0.92 m/s; Stage 3 Morphology Optimization (depth ≤5.5m for cross-ventilation ≤2.5x floor height for single-sided, light shelves, atrium for deep plans >6m, ceiling ≥3.5m) target improved cross-ventilation path; Stage 4 Envelope Optimization (lightweight insulated walls U≤0.8 W/m²K - 200mm hollow block + 50mm insulation, reflective roof U≤0.8 - white aluminum, ventilated attic, low-e glazing SHGC ≤0.35, light colors). PROJECTED ENGINEERING PERFORMANCE:Operative temperature Top reduction 32.5→29.4°C (-3.1°C), air velocity Vi increase 0.09→0.92 m/s (10x), air changes per hour ACH 2.0→6.2 h⁻¹ (3.1x), Givoni compliance 8.8%→70% (61.2% increase), cooling load reduction 46% translating to ~₦2.1M annual savings for 34 offices at Federal Polytechnic Ede. This study provides first institutional office field dataset from Ede, Osun State to global thermal comfort databases, addressing West Africa underrepresentation (<4% in ASHRAE DB II) and offers practical engineering design guidelines for new TETFund institutional buildings and retrofitting prioritization supporting Sustainable Development Goals 11 (Sustainable Cities) and 13 (Climate Action). LICENSING AND AVAILABILITY:This preprint is licensed under Creative Commons Attribution 4.0 International (CC BY 4.0). It is original manuscript pre-peer-review per Elsevier sharing policy for Journal of Building Engineering. Funding: TETFund IBR Grant FPE/DRD/IBR/17-21/B6/2025/10. Ethics: FPE/REC/2026/04/182 applied for - undertaking to provide formal letter upon issuance. Data: 10-year climatic (2013-2023), physical measurements (34 offices, 14 days, thrice daily), morphological (WWR, depth, orientation), occupant survey (n=182, ASHRAE 7-point), Givoni calculations - available as supplementary material upon acceptance and will be deposited in Zenodo community. Two publications from same dataset but distinct focus per COPE: (1) Journal of Building Physics Q3 IF 2.3 Performance & Adaptive Response - diurnal collapse 83%→27.5%, morphology-airflow association, (2) Journal of Building Engineering Q1 IF 8.1 Optimization & Energy Efficiency - framework, 70% Givoni, 46% cooling, ACH 6.2 - this preprint. For citation: Alabi, O.O., Morakinyo, K.O., & Adeleke, J.O. (2026). Engineering Optimization of Natural Ventilation for Thermal Comfort and Energy Efficiency in Institutional Office Buildings in Hot-Humid Ede, Nigeria: A Field Evidence-Based Four-Stage Framework. Zenodo Preprint. https://doi.org/10.5281/zenodo.