Walls

Walls are the primary component of the building envelope, separating conditioned spaces from the outdoors and other unconditioned areas.

You work with walls in Building Model → Envelope, on the Walls tab.

Assigning Wall Types

HVAKR treats every space edge as a potential wall. An edge on the building perimeter is exterior; an edge shared between two spaces is interior. You assign wall types to those edges either automatically or by hand.

Auto Create Envelope

The fastest way to assign walls is Auto Create Envelope (the ✨ button in the toolbar). It applies the Wall Type you choose to every unassigned exterior edge, across All Levels or only the current level (Level N). It skips wall assignment for spaces that have no slab-to-slab height. With a wall type selected, you can also turn on:

• Separate wall load between ceiling and space — the same option as on each wall (see Wall Data)
• Assign windows as percentage of wall area — adds one window at the center of each new wall, sized from the Wall Area Percent and Window Type you choose (see Windows and Doors)

If you also choose a Roof Type or Slab Type, those apply only to spaces on the building’s highest and lowest occupied levels — see Roof and Slab. Automations never override existing assignments, so it’s safe to run again as you add spaces.

Assign walls manually

1. On the Walls tab, click Assign Walls.
2. Choose Simple Wall (a single Wall Type) or Multi-Segment Wall (wall types stacked bottom to top, each with a height — the top segment auto-fills the remaining space height).
3. Under Options, leave Limit wall assignment to exterior on to ignore interior line segments, or turn it off to assign interior walls too. Optionally enable Separate wall load between ceiling and space.
4. Click Assign Walls.
5. Click walls on the canvas to assign the wall type, or drag a box to assign every wall inside it. Click a wall that already has the chosen wall type to clear it.
6. Click Done in the sidebar, or the check button at the top right of the canvas, to finish. The X button next to it cancels.

Edit a wall

Select a wall from the Walls list, or click it on the canvas, to open the Wall Data panel. Drag a box on the canvas to select several walls; a change in Wall Data then applies to all of them.

Wall Data

Selecting a wall opens Wall Data, where you can set:

• Simple Wall / Multi-Segment Wall — switch between a single assembly and a stack of wall types by height. Segments are ordered bottom to top, and the top segment’s height auto-fills the remaining space height.
• Wall Type — links to the wall type definition from Basis of Design, which supplies the Overall U-Value, Wall Mass Data, and Surface Absorptance used in the calculations.
• Wall Angle — the surface tilt, defaulting to 90° (vertical). The cooling calculation uses it for the solar gain on the wall.
• Separate wall load between ceiling and space — splits the wall’s cooling load between the space and the ceiling plenum. The space keeps the ceiling height ÷ slab-to-slab height share, and the ceiling plenum gets the rest.

The Wall Data header carries Locate (or press L), which fits the canvas around the selected walls. Copy Wall Properties and Paste Wall Properties sit next to it. Delete removes the wall assignment from the selected edges, including their windows and doors.

Orientation and area aren’t set here — HVAKR derives them automatically from the wall’s geometry and the building’s Plan Rotation, and uses them for the transmission and solar calculations.

Interior vs. Exterior

HVAKR uses exterior and interior only to decide which edges get a wall type — Auto Create Envelope and Limit wall assignment to exterior skip interior edges. The calculation does not tell them apart. It treats every edge that has a wall type as a wall to the outdoors, and every edge without one as having no heat transfer.

Walls with a wall type

For each assigned wall, HVAKR calculates:

• Cooling conduction from the hourly sol-air temperature, which includes solar gain from the wall type’s Surface Absorptance
• Heating conduction from the winter outdoor design temperature
• Wall and perimeter infiltration, which use the length and area of the assigned walls
• The slab perimeter for the F-Factor method (see Slab)

Because of this, a wall type on an edge between two conditioned spaces adds a load as if that edge faced the outdoors. Leave those edges unassigned when the spaces are at similar temperatures.

Walls to unconditioned spaces or soil

HVAKR has no dedicated below-grade or adjacent-space wall mode. To model a wall against soil, or against an unconditioned space such as a warehouse or garage, use a wall type with a Summer and Winter External Temperature Override set to the ground or adjacent-space temperature. Both are advanced fields on the wall type in Basis of Design → Building Data. When the Summer override is set, HVAKR uses it in place of the sol-air temperature, so the wall gets no solar gain.

Modeling Considerations

Thermal Bridges

Account for structural elements that bypass insulation by setting an effective Overall U-Value on the wall type:

• Steel studs through insulation
• Concrete slab edges
• Window frames and mullions

Common Issues

No Wall Types Defined

If a project has spaces but no wall types, the project Check warns that walls won’t contribute to load calculations. Define at least one wall type in Basis of Design → Building Data, then assign it.

Unassigned Exterior Walls

Exterior edges without a wall type don’t transmit heat, which understates loads. Run Auto Create Envelope or Assign Walls so every exterior edge is covered.

Incorrect Orientation

Because orientation is derived from geometry, make sure the plan is oriented correctly — the Plan Rotation dial on the Sheets & Maps toolbar sets the building’s north, and an incorrect rotation skews the solar calculations.