Envelope Overview
The building envelope separates conditioned interior spaces from the outdoors and unconditioned areas. Properly defining the envelope is critical for accurate load calculations.
Envelope Components
Section titled “Envelope Components”Exterior walls that separate conditioned spaces from outdoors. Each wall segment needs:
- Wall type (defines U-value and mass)
- Orientation (affects solar loads)
- Area (calculated from geometry)
Windows and Doors
Section titled “Windows and Doors”Openings in the exterior envelope:
- Window type (U-value and SHGC)
- Door type (U-value)
- Orientation and area
The roof assembly above conditioned spaces:
- Roof type (U-value and color)
- Area
- Skylight assignments
Floor construction for ground-level spaces:
- Slab type (edge and under-slab insulation)
- Perimeter length
Automatic Envelope Detection
Section titled “Automatic Envelope Detection”HVAKR automatically detects envelope boundaries based on space geometry:
- Exterior walls - Identified where space boundaries align with building perimeter
- Interior walls - Identified where spaces share boundaries
- Roof/ceiling - Assigned to top-floor spaces
- Slab - Assigned to ground-floor spaces
Review automatic assignments and adjust as needed.
Manual Envelope Assignment
Section titled “Manual Envelope Assignment”Override automatic detection when needed:
Assign Wall Type
Section titled “Assign Wall Type”- Select a space boundary segment
- Choose a wall type from the dropdown
- Specify interior or exterior
Add Windows
Section titled “Add Windows”- Select a wall segment
- Click Add Window
- Enter the window dimensions or count
- Assign a window type
Configure Roof
Section titled “Configure Roof”- Select a space
- Go to the Roof tab
- Assign a roof type
- Add skylights if applicable
Envelope Validation
Section titled “Envelope Validation”HVAKR validates your envelope and alerts you to:
- Missing assignments - Exterior boundaries without wall types
- Inconsistent boundaries - Adjacent spaces with conflicting assignments
- Invalid areas - Window area exceeding wall area
Impact on Calculations
Section titled “Impact on Calculations”The envelope affects:
- Transmission loads - Heat transfer through walls, roof, and floor
- Solar loads - Heat gain through windows and skylights
- Infiltration - Air leakage (based on envelope tightness)
Best Practices
Section titled “Best Practices”- Verify automatic detection - Check that HVAKR correctly identified exterior vs. interior
- Assign types before windows - Set wall types first, then add windows
- Check orientations - Verify cardinal directions for solar calculations
- Account for all openings - Include all windows and doors
- Consider shading - Add external shading devices where applicable