Missing or Zero Loads

When loads don’t appear, are partially missing, or read zero, the cause is almost always an unassigned input rather than a calculation problem. Work through the cases below.

Loads aren’t showing at all

Loads will not generate unless each space has a space type assigned. The space type defines the design requirements (internal loads, ventilation, setpoints) and links them to the space geometry.

To fix:

1. Select a space in the Spaces pane.
2. In the Space Data sidebar, assign a space type using the dropdown.

Once space types are assigned, loads populate accordingly. See Space Types.

A space shows a low or unexpected BTU despite having exterior walls

Two different design-condition fields on the space type cause two different problems. Don’t treat them as the same issue.

Missing Summer (Cooling) or Winter (Heating) setpoint. Every envelope load (walls, windows, roof, skylights, slabs, doors) and every ventilation/infiltration load — sensible and latent — needs the matching setpoint to calculate. Without it, HVAKR zeros that entire load path for that condition. The two conditions then behave differently:

• Cooling — internal gains (people, lighting, equipment) don’t depend on the setpoint, so they still calculate. The cooling total isn’t always exactly 0 BTU. Only the envelope, ventilation, and infiltration components drop out.
• Heating — the heating load takes no credit for people, lighting, or equipment. Its only internal term is the space’s Misc. Heating Load. So without a Winter (Heating) setpoint, the heating total is that value, which is usually 0 BTU.

Missing Relative Humidity. This field affects the cooling load only. It removes the latent portion of the ventilation and general/window infiltration cooling loads. It also removes the door infiltration cooling load entirely — both sensible and latent — because HVAKR calculates door infiltration’s cooling sensible and latent loads together and needs relative humidity for both. Envelope loads and the other sensible ventilation/infiltration loads are unaffected. Heating loads don’t use relative humidity, so heating door infiltration still calculates.

To fix:

1. Go to Basis of Design → Space Types.
2. Select the affected space type.
3. Add the Summer (Cooling) setpoint, Winter (Heating) setpoint, and Relative Humidity values.

Loads will then calculate normally for every space using that type.

External cooling loads (walls, windows) are missing

External loads will not appear in the Cooling Sums at Peak unless the envelope types have Wall Mass Data, Window Mass Data, and Roof Mass Data assigned.

To fix:

1. Go to Basis of Design → Building Data.
2. Open each relevant wall, window, and roof type.
3. Select the closest available assembly type for each data field.

Tip

The assembly does not need to be exact — the closest available type is enough to produce results. Wall and Roof Mass Data set the conduction time series (thermal mass delay). Window Mass Data sets how the window’s SHGC changes with the sun’s angle. The radiant time series comes from the Building CTS Data selection, not from these types.

Once Wall, Window, and Roof Mass Data are assigned, the external cooling loads appear in the results. See Building Data.

Infiltration CFM is lower than expected

Reported infiltration can come in low if some spaces with exterior wall area are missing a space type. This applies to every infiltration method, and to spaces with their own infiltration override.

Infiltration is only calculated for fully defined spaces. A space without a space type can still contribute its wall area to the project total, but its infiltration is excluded from the load calculation — so the totals diverge.

To fix, confirm every space with exterior wall area has a space type assigned. Once assigned, the infiltration total updates accordingly.

Note

This is the same root cause as missing loads above: an unassigned space type silently drops that space from parts of the calculation while its geometry still shows up in area totals.