# HVAC Load Calculator Web Application Design

## Overview
This document outlines the structure and user flow for the HVAC Load Calculator web application. The application will be built using Python and deployed on Hugging Face Spaces, providing a user-friendly interface for calculating cooling and heating loads based on the ASHRAE method.

## Application Structure

### 1. Core Components
- **Backend Calculation Modules**
  - `cooling_load.py`: Implements ASHRAE cooling load calculations
  - `heating_load.py`: Implements ASHRAE heating load calculations
  - `reference_data.py`: Contains material properties, climate data, and other reference information

- **Web Interface**
  - `app.py`: Main Streamlit application entry point
  - `pages/`: Directory containing individual calculator pages
    - `cooling_calculator.py`: Cooling load calculator interface
    - `heating_calculator.py`: Heating load calculator interface
    - `about.py`: Information about the application and calculation methods
  
- **Utilities**
  - `utils/`: Directory containing utility functions
    - `validation.py`: Input validation functions
    - `visualization.py`: Chart and table generation functions
    - `export.py`: Data export functionality

### 2. Data Flow
```
User Input → Validation → Calculation → Results Visualization → Data Export
```

## User Flow

### Home Page
- Introduction to the application
- Selection between cooling and heating load calculators
- Information about ASHRAE calculation methods
- Links to reference materials

### Cooling Load Calculator
1. **Building Information**
   - Building location
   - Indoor and outdoor design temperatures
   - Building dimensions and volume

2. **Building Envelope**
   - Wall areas and construction types
   - Roof/ceiling areas and construction types
   - Floor areas and construction types

3. **Windows and Doors**
   - Window areas by orientation
   - Glass types and shading information
   - Door areas and types

4. **Internal Loads**
   - Number of occupants
   - Lighting information
   - Equipment and appliances

5. **Ventilation and Infiltration**
   - Air changes per hour
   - Ventilation requirements

6. **Results**
   - Breakdown of cooling loads by component
   - Total sensible and latent cooling loads
   - Visualizations (charts and tables)
   - Equipment sizing recommendations
   - Option to download input and result data

### Heating Load Calculator
1. **Building Information**
   - Building location
   - Indoor and outdoor design temperatures
   - Building dimensions and volume

2. **Building Envelope**
   - Wall areas and construction types
   - Roof/ceiling areas and construction types
   - Floor areas and construction types

3. **Windows and Doors**
   - Window areas by orientation
   - Glass types
   - Door areas and types

4. **Ventilation and Infiltration**
   - Air changes per hour
   - Ventilation requirements

5. **Occupancy Information**
   - Occupancy type and schedule
   - Heating degree days information

6. **Results**
   - Breakdown of heating loads by component
   - Total peak heating load
   - Annual heating energy requirement
   - Visualizations (charts and tables)
   - Equipment sizing recommendations
   - Option to download input and result data

## User Interface Design

### General Principles
- Clean, modern interface with clear navigation
- Step-by-step input forms with progress indicators
- Immediate feedback on inputs with validation warnings
- Informative tooltips and help text for technical terms
- Responsive design for different screen sizes

### Input Forms
- Grouped by logical sections
- Clear labels and units
- Default values where appropriate
- Input validation with warning messages
- Option to proceed with warnings rather than blocking progress
- Reference data selection for materials and locations

### Results Display
- Clear summary of key results
- Detailed breakdown of load components
- Visual representations (charts and graphs)
- Tabular data for detailed analysis
- Equipment sizing recommendations
- Export options for reports and assignments

## Validation System
- Input validation for required fields
- Range checking for numerical inputs
- Logical validation between related inputs
- Warning system that allows proceeding with caution
- Clear error messages with suggestions for correction

## Data Export Functionality
- Export input data in JSON format
- Export results in CSV format
- Generate PDF reports with inputs and results
- Save charts and visualizations as images

## Extensibility Features
- Modular code structure for easy addition of new calculation methods
- Configuration-based reference data for easy updates
- Pluggable visualization components
- Separation of UI and calculation logic

## Technology Stack
- **Backend**: Python
- **Web Framework**: Streamlit
- **Data Processing**: Pandas, NumPy
- **Visualization**: Plotly, Matplotlib
- **Deployment**: Hugging Face Spaces