Building Data

Building properties define the thermal characteristics of your building envelope. These properties are used to calculate transmission heat losses and gains.

At the top of Basis of Design > Building Data, a card captures project-level building info:

• Building Name (optional) - Free-text name for the building
• Description (optional) - Longer description of the building
• Total Floor Area - Read-only sum of all space floor areas
• Number of Levels - Read-only count of unique levels that have spaces
• Occupancy - Read-only sum of occupancy across all spaces after applying diversity
• Building Type - Selects ASHRAE Conductive Time Series (CTS) data for the building. CTS describes how heat conducts through the envelope over time; heavy vs. light mass constructions store and release heat differently, which affects radiant time series (RTS) load calculations

Each envelope type section below has Create and Import buttons, plus a gear icon that toggles Advanced Settings for that table.

Wall Types

Wall types define the thermal resistance of exterior and interior walls.

Properties

• Wall Type - Descriptive name (e.g., “6-inch CMU with Insulation”)
• Wall Mass Data - The ASHRAE wall construction, which determines the thermal mass used for time-delay (radiant time series) calculations
• Overall U-Value - Overall heat transfer coefficient (BTU/h-ft²-°F or W/m²-K)
• Surface Absorptance - Exterior surface solar absorptance (dark surfaces absorb more solar radiation)
• Color - Display color used when rendering the wall type on sheets

Advanced Settings

Click the gear icon (Advanced Settings) on the Wall Types header to reveal:

• Summer External Temperature Override - Optional fixed external temperature, e.g. for below-grade walls
• Winter External Temperature Override - Optional fixed external temperature for the heating case

Creating Wall Types

1. Go to Basis of Design > Building Data
2. Click Create Wall Type (or Import to pull in a template)
3. Enter the properties and select a construction from the ASHRAE library

ASHRAE Library

HVAKR includes a library of common wall constructions based on ASHRAE Fundamentals.

Window Types

Window types define the thermal and solar properties of glazing.

Properties

• Window Type - Descriptive name (e.g., “Double Pane Low-E”)
• Window Mass Data - The ASHRAE window construction (glazing and frame type)
• Overall U-Value - Heat transfer coefficient including frame
• SHGC - Solar Heat Gain Coefficient (0 to 1)

Advanced Settings

Click the gear icon (Advanced Settings) on the Window Types header to reveal infiltration columns:

• Summer Area Infiltration - Air leakage per window area
• Summer Perimeter Infiltration - Air leakage per window perimeter length
• Use Separate Winter Reqs - When checked, winter infiltration uses the winter rates below instead of the summer rates year-round
• Winter Area Infiltration - Winter air leakage per window area
• Winter Perimeter Infiltration - Winter air leakage per window perimeter length

SHGC (Solar Heat Gain Coefficient)

SHGC indicates how much solar radiation passes through the window:

• 0.25 - High-performance low-e, blocks most solar heat
• 0.40 - Standard low-e glazing
• 0.60 - Clear double pane
• 0.80 - Clear single pane

Lower SHGC reduces cooling loads but may reduce beneficial winter solar gain.

Door Types

Door types define thermal properties of exterior doors.

Properties

• Door Type - Descriptive name
• Overall U-Value - Heat transfer coefficient
• Surface Absorptance - Exterior surface solar absorptance
• Open Fraction - Fraction of time the door is open during the associated space’s usage

Advanced Settings

Click the gear icon (Advanced Settings) on the Door Types header to reveal:

• Seals - Whether the door has seals

Roof Types

Roof types define the thermal properties of the roof assembly.

Properties

• Roof Type - Descriptive name (e.g., “Built-up Roof with R-30”)
• Roof Mass Data - The ASHRAE roof construction, which determines the thermal mass used for time-delay calculations
• Overall U-Value - Overall heat transfer coefficient
• Surface Absorptance - Exterior surface solar absorptance (dark roofs absorb more solar radiation)
• Color - Display color used when rendering the roof type

Advanced Settings

Click the gear icon (Advanced Settings) on the Roof Types header to reveal:

• Summer External Temperature Override - Optional fixed external temperature, e.g. for roofs below unconditioned spaces
• Winter External Temperature Override - Optional fixed external temperature for the heating case

Slab Types

Slab types define floor construction for slab-on-grade and below-grade spaces.

Properties

• Slab Type - Descriptive name
• F-Factor - Slab-on-grade perimeter heat loss coefficient (BTU/h-ft-°F), which captures the effect of edge insulation
• Color - Display color used when rendering the slab type

Advanced Settings

Click the gear icon (Advanced Settings) on the Slab Types header to reveal:

• Summer External Temperature Override - Optional fixed external temperature for spaces below the slab
• Winter External Temperature Override - Optional fixed external temperature for the heating case
• Overall U-Value - Heat transfer coefficient used only when the slab type has an external temperature override (e.g. floors above unconditioned spaces)

Slab-on-Grade Heat Loss

Heat loss through slab-on-grade floors is calculated based on:

• Perimeter length
• F-factor (heat loss per linear foot of exposed edge)
• Indoor-outdoor temperature difference

Skylights

Skylights use window types for their thermal and solar properties — there is no separate skylight type. Assign a window type when creating skylights on a roof; HVAKR applies the appropriate solar angle calculations for horizontal glazing.

Best Practices

1. Start with library types - Use ASHRAE library values when possible
2. Verify U-values - Check that values match specifications
3. Consider all layers - Include air films in U-value calculations
4. Account for thermal bridges - Use effective U-values that include framing