# HeatBee: Surrogate Modeling of High-Mass Vernacular Architecture in Arid Climates

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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

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

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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

```bash
# 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:
```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}
}
```