Tech-Meld/HeatBee-Database

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).

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🎯 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.

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🔬 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

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⚡ 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

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⚠️ Limitations

1. 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.
2. Simplified Infiltration & Internal Loads: Constant occupancy sensible gains (2 people, 240 W) without dynamic appliance scheduling or variable occupant window operation.
3. 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.

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🚀 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

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📄 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}
}