HeatBee: Surrogate Modeling of High-Mass Vernacular Architecture in Arid Climates
HeatBee is an open-source building performance simulation pipeline and Machine Learning surrogate model investigating the transient thermodynamic behavior of vernacular rammed earth (pisé) architecture versus contemporary construction in Marrakesh, Morocco (Zone Climatique 5).
🎯 Key Physical Findings
Simulations were performed under the peak summer period of the Marrakesh Menara Airport EPW (peak outdoor dry-bulb: 45.52°C).
1. The Typology Comparison: Interior Mass vs. Envelope Insulation
- As-Built Typology (Mode A): A 50 cm pisé room (with earth partitions and floor) maintains a peak operative temperature of 30.63°C and 20.3 Discomfort Degree Hours (>30°C), compared to 31.48°C and 81.1 DDH for an RTCM Zone 5 modern room (20 cm hollow brick with 4 cm XPS insulation and 15 cm concrete slabs).
- Shared Interior Mass (Mode B): When both rooms are modeled with identical 15 cm concrete slab floors and partitions, the result equalizes: the RTCM-insulated room reaches 31.48°C (81.1 DDH), while the pisé room reaches 31.76°C (165.8 DDH).
- Takeaway: The vernacular advantage is driven primarily by interior volumetric thermal mass coupled with nocturnal free cooling, rather than the exterior earth wall possessing superior steady-state thermal resistance over continuous code insulation.
2. Component Apportionment (Wall vs. Roof)
Holding interior mass constant (15 cm concrete partitions for all), component swapping reveals:
- The 50 cm pisé exterior wall outperforms the RTCM insulated wall by 0.16°C (31.32°C vs 31.48°C peak), as extreme thermal inertia suppresses peak daytime flux.
- The traditional mud/timber roof is the primary thermal vulnerability, admitting +0.50°C of excess heat compared to the RTCM-insulated roof (31.98°C vs 31.48°C).
3. Realistic Ground-Coupled Boundary
- Under an adiabatic floor assumption (isolated upper-floor room), the pisé room peaks at 30.63°C.
- Under realistic summer ground coupling (Kusuda $24.0^\circ\text{C}$–$25.0^\circ\text{C}$ subsoil), downward heat dissipation drops the pisé room peak to 29.61°C, bringing it completely below the 30.0°C adaptive comfort limit during a 45.5°C heatwave.
4. Thermal Mass and Ventilation Sweeps
- Mass Diminishing Returns: Increasing pisé thickness from 15 cm to 45 cm reduces peak temperatures by 2.40°C, whereas adding another 30 cm (to 75 cm) yields only 0.71°C of marginal cooling. This aligns with the 1D periodic thermal penetration depth: $$\delta = \sqrt{\frac{k}{\rho c_p} \frac{P}{\pi}} \approx 11\text{ cm}$$ Beyond $4\delta \approx 44\text{ cm}$, the diurnal thermal wave is attenuated by ~98%.
- Nocturnal Ventilation: Increasing airflow from 0 to 4 ACH drops peak temperatures by 1.46°C, but tripling airflow from 4 to 12 ACH yields only 0.51°C of additional relief as indoor air approaches ambient night temperature.
🔬 Benchmark Comparison (July–August Peak Heatwave)
Shared boundary conditions: Roof albedo 0.60, external wall solar absorptance 0.50, glazing SHGC 0.40, 4.0 ACH free cooling, adiabatic perimeter.
| Archetype | Peak Temp [°C] | Mean Temp [°C] | DDH (>30°C) | Decrement ($f$) |
|---|---|---|---|---|
| Ambient Outdoor (Menara EPW) | 45.52 | 29.67 | 3642.2 | 1.00 |
| Modern Uninsulated (20cm Hollow Brick, Brick Floor) | 35.21 | 28.68 | 740.1 | 0.34 |
| Modern RTCM Zone 5 (4cm XPS, 15cm Concrete Slab) | 31.48 | 28.14 | 81.1 | 0.12 |
| Vernacular Medina Riad (50cm Pisé, Pisé Floor) | 30.63 | 28.24 | 20.3 | 0.14 |
| Riad with Concrete Slab Floor (Mode B) | 31.76 | 28.45 | 165.8 | 0.13 |
⚡ Machine Learning Surrogate Fidelity
- Model: Gradient Boosted Decision Trees (
XGBoostRegressor) - Training Dataset: 256 Latin Hypercube samples evaluated via EnergyPlus 26.2
ConductionFiniteDifference - 5-Fold Cross Validation: $R^2 = 0.9450$ | $\text{RMSE} = 0.358^\circ\text{C}$ | $\text{MAE} = 0.275^\circ\text{C}$ (Spread $\sigma = 1.53^\circ\text{C}$)
- Out-of-Sample Holdout (N=32 Unseen Runs, Seed 999): $\text{RMSE} = 0.316^\circ\text{C}$ | $\text{MAE} = 0.262^\circ\text{C}$
- Inference Latency: $< 1\text{ ms}$ on CPU
⚠️ Limitations
- Single-Zone Idealization: The model represents an isolated single-room perimeter zone facing an exterior aperture, not a fully coupled 3D computational fluid dynamics (CFD) courtyard void.
- Simplified Infiltration & Internal Loads: Constant occupancy sensible gains (2 people, 240 W) without dynamic appliance scheduling or variable occupant window operation.
- No Sensor Calibration: This is a numerical comparative simulation; boundary conditions have not yet been calibrated against empirical data-logger measurements from historic medina structures.
🚀 Quickstart
# 1. Clone repository
git clone https://github.com/<your-username>/HeatBee.git
cd HeatBee
# 2. Install dependencies
pip install -r requirements.txt
# 3. Run verified benchmark, sweeps, and holdout validation
python cli.py --benchmark
python cli.py --sweeps
python cli.py --holdout
# 4. Launch interactive dashboard
streamlit run app.py
📄 Citation & License
MIT License. If citing this software or dataset:
@software{heatbee2026,
author = {Haytam Aarab},
title = {HeatBee: Surrogate Modeling of High-Mass Vernacular Architecture in Arid Climates},
year = {2026},
publisher = {Zenodo},
doi = {10.5281/zenodo.23145635}
}