| # HeatBee: Surrogate Modeling of High-Mass Vernacular Architecture in Arid Climates |
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| [](https://energyplus.net/) |
| [](https://www.python.org/) |
| [](https://xgboost.readthedocs.io/) |
| [](LICENSE) |
| [](https://doi.org/10.5281/zenodo.23145635) |
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| 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 |
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| Simulations were performed under the peak summer period of the Marrakesh Menara Airport EPW (peak outdoor dry-bulb: **45.52°C**). |
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| ### 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. |
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| ### 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). |
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| ### 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. |
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| ### 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) |
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| *Shared boundary conditions: Roof albedo 0.60, external wall solar absorptance 0.50, glazing SHGC 0.40, 4.0 ACH free cooling, adiabatic perimeter.* |
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| | 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 |
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| * **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 |
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| 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 |
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| ```bash |
| # 1. Clone repository |
| git clone https://github.com/<your-username>/HeatBee.git |
| cd HeatBee |
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| # 2. Install dependencies |
| pip install -r requirements.txt |
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| # 3. Run verified benchmark, sweeps, and holdout validation |
| python cli.py --benchmark |
| python cli.py --sweeps |
| python cli.py --holdout |
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| # 4. Launch interactive dashboard |
| streamlit run app.py |
| ``` |
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| --- |
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| ## 📄 Citation & License |
| MIT License. If citing this software or dataset: |
| ```bibtex |
| @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} |
| } |
| ``` |
