Climatic Analysis of Ventilation and Thermal Performance of a Dome Building with Roof Vent

Overview

Authors: Zohreh Soleimani (University of Bath), John Kaiser Calautit, Katrina Calautit (University of Nottingham), Ben Richard Hughes (University of Sheffield). Published in ICE Engineering Sustainability, Vol. 171(8), 2018.

Comprehensive CFD analysis of a naturally ventilated geodesic dome building across all 12 months in Yazd, Iran (BWh hot desert climate). Uses ANSYS FLUENT15 with standard k-epsilon turbulence model, 4.67M element unstructured mesh.

Dome Specification

• 3V Icosahedron geodesic dome (smoother than 2V, lower complexity than 4V)
• Two-floor building, total height 9.06 metres
• Based floor area 143 m², volume 864 m³
• Multi-directional roof vent for natural ventilation
• 30% less surface area than equivalent box building
• 18 measurement points at 1.2m (lower floor) and 4.2m (upper floor)

Critical Finding: Summer Cooling Failure

Roof vent alone acts as “air curtain” — it supplies fresh air but does NOT effectively exhaust warm air. During summer months (38-41°C outdoor), PMV values all above +3 (Hot on ASHRAE scale). Natural ventilation through roof vents alone cannot satisfy thermal requirements.

Thermal Data

• At 14°C outdoor: lower floor averaged 35.4°C, upper floor 32.3°C
• Lower floor 3.14°C warmer than upper floor on average
• Upper floor airflow velocity 28% higher than lower floor
• Lowest temperature (17°C) near roof vents; highest (37°C) in bottom-right low-airflow corner
• Ventilation rate: 7.7 l/s per m² at 3.0 m/s wind speed

Why It Fails

Roof vent creates swirling recirculation flows on upper floor, producing uneven thermal and airflow distribution between floors. The vent captures approaching airflow and redirects to leeward wall, forming large recirculation rather than effective exhaust.

Recommended Solutions (from authors)

1. Lower openings must be added to complement roof vents (enable stack effect through-flow)
2. Divider in roof vent could improve ventilation strategy (separate inlet/outlet zones)
3. Inlet and outlet shafts could improve flow directionality
4. Thermal mass with night cooling for summer performance
5. Evaporative cooling, heat pipes, PCMs, or desiccant dehumidification for hot-humid climates

Arched Roof Vent Optimization (Li et al., 2020)

A companion study on arched (curved-roof) greenhouses demonstrates what optimized vent placement achieves:

• Three vent types tested: Rolling Shutter (RS), Jack-up (JU), Pivoting Window (PW)
• Rolling Shutter at 75° position angle: 2.66× higher ventilation flow rate than PW
• RS achieved 1.5°C additional cooling within 10 minutes vs. existing PW design
• Position angle of 85° identified as optimal for most configurations
• Temperature inhomogeneity decreased 33.3%, velocity inhomogeneity reduced 11.89%
• The “air curtain” effect in PW vents parallels the same phenomenon in dome roof vents

This demonstrates that vent type and position angle optimization on curved roofs can yield dramatic improvements — the approach the dome studies call for but do not perform.