Building Data

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

Wall Types

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

Properties

• Name - Descriptive name (e.g., “6-inch CMU with Insulation”)
• Wall 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
• Summer/Winter External Temperature Override - Optional fixed external temperatures, e.g. for below-grade walls

Creating Wall Types

1. Go to Basis of Design > Building Data
2. Add a row to the Wall Types table
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

• Name - Descriptive name (e.g., “Double Pane Low-E”)
• Window 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)
• Infiltration - Air leakage rates per window area and perimeter, with optional separate winter values

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.

Roof Types

Roof types define the thermal properties of the roof assembly.

Properties

• Name - Descriptive name (e.g., “Built-up Roof with R-30”)
• Roof 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
• Summer/Winter External Temperature Override - Optional fixed external temperatures, e.g. for roofs below unconditioned spaces

Slab Types

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

Properties

• Name - Descriptive name
• F-Factor - Slab-on-grade perimeter heat loss coefficient (BTU/h-ft-°F), which captures the effect of edge insulation
• Overall U-Value - Heat transfer coefficient, used for floors above unconditioned spaces
• Color - Display color used when rendering the slab type
• Summer/Winter External Temperature Override - Optional fixed external temperatures for spaces below the slab

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

Door Types

Door types define thermal properties of exterior doors.

Properties

• Name - 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 space’s usage
• Seals - Whether the door has seals

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