Sensitivity Analysis

How to use what-if scenarios to understand how input changes affect loads and equipment sizing.

Running What-If Scenarios

From any completed Manual J calculation, open the sensitivity panel. Change any input — window type, insulation R-value, infiltration rate, orientation — and see the load impact instantly. The results update in real time showing the change in BTU/hr for heating and cooling, and whether the equipment sizing changes.

Comparing Scenarios

Save multiple scenarios and compare them side by side. Each scenario shows total heating load, total cooling load, SHR, and recommended equipment size. Use this to evaluate upgrade options: 'What if the homeowner upgrades from double-pane to triple-pane windows? How much does the load drop and does it change the equipment recommendation?'

Uncertainty Flagging

Inputs marked as 'assumed' (not measured in the field) are highlighted in the sensitivity panel with their impact ranking. The highest-impact assumptions are flagged: 'Infiltration rate is assumed. A +/- 0.2 ACH change would shift the heating load by +/- 4,200 BTU/hr.' This tells you which field measurements are worth making.

Sensitivity Analysis

Running What-If Scenarios

Comparing Scenarios

Uncertainty Flagging

More documentation

Manual J Load Calculation

Equipment Selection (Manual S)

Duct Design (Manual D)

Heat Pump Design Workflow

Psychrometric Analysis

Reports and Export

Building Envelope Library

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