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Building Properties

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

Wall Types

Section titled “Wall Types”

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

Properties

Section titled “Properties”
  • Name - Descriptive name (e.g., “6-inch CMU with Insulation”)
  • U-Value - Overall heat transfer coefficient (BTU/h-ft²-°F or W/m²-K)
  • Mass - Wall mass category affects the time delay of heat transfer
  • Color - Exterior surface color affects solar absorption

Creating Wall Types

Section titled “Creating Wall Types”
  1. Go to Basis of Design > Building
  2. Click Add Wall Type
  3. Enter the properties or select from the ASHRAE library

ASHRAE Library

Section titled “ASHRAE Library”

HVAKR includes a library of common wall constructions with pre-calculated U-values based on ASHRAE Fundamentals.

Window Types

Section titled “Window Types”

Window types define the thermal and solar properties of glazing.

Properties

Section titled “Properties”
  • Name - Descriptive name (e.g., “Double Pane Low-E”)
  • U-Value - Heat transfer coefficient including frame
  • SHGC - Solar Heat Gain Coefficient (0 to 1)
  • VT - Visible Transmittance (affects daylighting calculations)
  • Frame Type - Aluminum, wood, vinyl, etc.

SHGC (Solar Heat Gain Coefficient)

Section titled “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

Section titled “Roof Types”

Roof types define the thermal properties of the roof assembly.

Properties

Section titled “Properties”
  • Name - Descriptive name (e.g., “Built-up Roof with R-30”)
  • U-Value - Overall heat transfer coefficient
  • Color - Affects solar absorption (dark, medium, light)
  • Suspended Ceiling - Whether a plenum exists below the roof

Attics and Plenums

Section titled “Attics and Plenums”

For buildings with attic spaces, configure:

  • Attic ventilation rate
  • Ceiling U-value (separate from roof U-value)

Slab Types

Section titled “Slab Types”

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

Properties

Section titled “Properties”
  • Name - Descriptive name
  • Edge Insulation - R-value of perimeter insulation
  • Under-Slab Insulation - R-value below the slab
  • Type - Slab-on-grade, basement, or crawlspace

Slab-on-Grade Heat Loss

Section titled “Slab-on-Grade Heat Loss”

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

  • Perimeter length
  • Soil conditions
  • Edge insulation

Door Types

Section titled “Door Types”

Door types define thermal properties of exterior doors.

Properties

Section titled “Properties”
  • Name - Descriptive name
  • U-Value - Heat transfer coefficient
  • Type - Solid, glass, or combination

Skylight Types

Section titled “Skylight Types”

Skylights are treated similarly to windows but with different solar angle calculations.

Properties

Section titled “Properties”
  • Name - Descriptive name
  • U-Value - Heat transfer coefficient
  • SHGC - Solar Heat Gain Coefficient
  • Curb Height - Height above the roof surface

Best Practices

Section titled “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