Where Your Loads Come From

Most load and ventilation values in HVAKR start at the space’s space type. Use this page when a number in Loads or Ventilation is not what you expect and you want to find the input that sets it.

Each space’s results come from this chain:

1. Space type: default rates per person and per unit area. See Space Types.
2. Space: area, height, envelope, and values that replace or add to the space type defaults. See Spaces.
3. Usage schedule: the space type’s 24-hour profile that scales internal and process loads hour by hour.
4. Ventilation standard: turns the space type’s outdoor air (OA) rates into an airflow. See ASHRAE 62.1.
5. System: the central unit’s Outside Air method sets the outdoor air the unit draws. See Ventilation.

Space type defaults

Set these values on Basis of Design > Space Types. A change to a space type changes every space that uses it.

Space type input	Section	What it sets
People Density	Interior Loads	Occupancy: density × area. Occupancy drives the people loads and the people part of the outdoor air
People Sensible Load, People Latent Load	Interior Loads	Heat per person. Occupancy × this value gives the People Sensible and People Latent lines
Lighting Load	Interior Loads	Lighting heat: W/ft² (or W/m²) × area. Lighting Load to Ceiling Space sends part of it to the plenum (Lighting to Plenum)
Equipment Load	Interior Loads	Equipment heat: W/ft² (or W/m²) × area
People Outdoor Air (Rp), Area Outdoor Air (Ra), Ez	Ventilation Requirements	The ventilation requirement of each space. See Where outdoor air comes from
Outdoor Air Changes	Ventilation Requirements (Advanced Settings)	A minimum outdoor airflow in air changes per hour (Vach)
Schedule	Usage Schedule	The hourly multiplier for people, lighting, equipment, and misc. cooling loads

Some space fields replace or add to these defaults. Set them in the Spaces table:

• Occupancy: replaces people density × area. Reset the field to go back to Calculated.
• Misc. Cooling Sensible Load and Misc. Cooling Latent Load: add a cooling load that the space type does not cover, such as process or kitchen equipment. The space type’s schedule scales these loads.
• Misc. Heating Load: adds a heating load. The schedule does not scale it.
• Ventilation: sets the outdoor air method of the space. See Override outdoor air.

If a space has no space type, HVAKR does not calculate its loads. See Missing or Zero Loads.

How schedules scale loads

Each space type has one Schedule: 24 hourly multipliers from 0.0 to 1.0. For each hour, HVAKR multiplies these cooling loads by the multiplier for that hour:

• People sensible and people latent
• Lighting
• Equipment
• The space’s Misc. Cooling Sensible Load and Misc. Cooling Latent Load
• Door infiltration (the door open fraction)

The schedule does not scale envelope loads, the ventilation requirement, or heating loads. Heating takes no credit for people, lighting, or equipment. A space type with no schedule uses a 24/7 schedule (1.0 at every hour).

The cooling peak is the hour with the largest total load. Thus the multiplier near the peak hour sets how much internal load you see in Cooling Sums at Peak. Stored heat from the radiant part of a load releases over the next hours, so a load can still show for some hours after its multiplier drops.

A schedule can hide a load

• Zero or low multipliers. A schedule that is 0.0 at an hour removes all internal loads and misc. cooling loads of the space at that hour. A 9am–5pm schedule on a space that peaks at 6 pm shows only the stored part of these loads. A schedule that is 0.0 at all hours removes them at all hours.
• 24/7 schedule on a part-time space. A 24/7 schedule holds each load at its full value at every hour. The full load is there, but it does not change with time, so it does not move the peak and is easy to miss in the hourly profile. It also adds load at hours when the space is not in use.
• One schedule per space type. People, lighting, equipment, and misc. cooling loads all use the same schedule. If a process load (for example, gas cooking equipment) operates on a different profile, put it in a space with its own space type and schedule.

To check a schedule, open the space type on Basis of Design > Space Types, go to the Usage Schedule section, and look at the multiplier near the peak hour of the space. See Usage Schedule.

Where outdoor air comes from

On the default VRP method, the outdoor air of each space comes from its space type rates and the ASHRAE 62.1 Ventilation Rate Procedure:

Vbz  = Rp × Pz + Ra × Az
Voz  = Vbz / Ez
Vreq = max(Voz, Vach) × EQ

• Rp is the space type’s People Outdoor Air and Pz is the space’s occupancy.
• Ra is the space type’s Area Outdoor Air and Az is the space’s area.
• Ez is the space type’s Ez.
• Vach is the space type’s Outdoor Air Changes minimum.
• EQ is the air density correction factor. It applies only to the 2025 ASHRAE edition. Select the standard and edition in Settings.

The HVAKR ASHRAE 62.1 space type templates fill Rp and Ra with the rates from the standard. The schedule does not reduce the outdoor air requirement. Thus a space with low internal loads can still have a large outdoor airflow. For the full calculation, see Ventilation.

The Ventilation page shows outdoor airflow (for example, cfm), not heat. The heat of the outdoor air shows on the Loads page as Ventilation Total in System Sensible & Latent Components (cooling) and System Sensible Components (heating). Space Sensible Components does not include ventilation.

Override outdoor air

Per space type

Use this to change the outdoor air of all spaces of one type, for example all corridors.

1. Go to Basis of Design > Space Types.
2. In Ventilation Requirements, change People Outdoor Air, Area Outdoor Air, or Ez for the space type.
3. To set an air change minimum, click the sliders icon (Advanced Settings) and change Outdoor Air Changes.

Every space that uses the type recalculates. Example: a corridor type has People Outdoor Air 0 cfm/person and Area Outdoor Air 0.06 cfm/ft². To give all corridors 0.10 cfm/ft², set Area Outdoor Air to 0.10 on the corridor type. To change only some corridors, create a second corridor space type and assign it to those spaces.

Per space

Use this to set the outdoor airflow of one space.

1. Go to the Spaces table, or to Reports > Ventilation.
2. In the Ventilation column (Spaces) or the Method column (Ventilation), select Custom.
3. Type the outdoor airflow.

The custom airflow replaces Vreq for the design. HVAKR still calculates Vreq and flags a custom value that is below it. A custom airflow does not update when occupancy, the space type, or the area changes.

To change only the people part of the outdoor air of one space, set its Occupancy instead.

Per system

The central unit’s Outside Air method (Sum of Spaces, Multi-Zone, Percent, or Custom) sets the outdoor air the unit draws. Percent and Custom bypass the space requirements. See Outside Air Method.

Check a number in the results

1. Go to Reports > Loads and select the space in the sidebar.
2. In Cooling Sums at Peak, find the line in Space Sensible Components (People Sensible, Lighting, Equipment, Miscellaneous Sensible) or in System Sensible & Latent Components (People Latent, Miscellaneous Latent, Ventilation Total).
3. Find the inputs for that line: the space type rate, the space area or Occupancy, and the schedule multiplier near the peak hour.
4. Multiply them and compare with the line.

Example: a 1,000 ft² space has a Lighting Load of 0.8 W/ft², Lighting Load to Ceiling Space of 0%, and a 24/7 schedule. The lighting heat is 0.8 × 1,000 = 800 W, and 800 W × 3.412 = 2,730 BTU/h. The Lighting line shows about 2,730 BTU/h at every hour. With a schedule below 1.0 near the peak, the line is lower; it does not match the instant value exactly because stored heat releases over time.

To check outdoor air:

1. Go to Reports > Ventilation and find the space row.
2. Compare the People OA Rate, Area OA Rate, and Ez columns with the space type.
3. Calculate Voz and compare it with the Voz (VRP) column.

Example: a 400 ft² corridor with Rp = 0, Ra = 0.06 cfm/ft², and Ez = 0.8 gives Vbz = 0.06 × 400 = 24 cfm and Voz = 24 / 0.8 = 30 cfm.

If a line is zero or missing, see Missing or Zero Loads. If a line is higher than you expect, see Unexpected Load Values. For each line of the Loads page, see Loads Summary.