VALICALC · ENGINEERING WORKFLOW
Heating load to heat-pump capacity check
Build an envelope and outdoor-air heat-loss estimate, compare a heat-pump capacity basis, then separate peak kW from annual kWh and running cost.
Start this workflowWhat do I need to know first?
- Indoor/outdoor design temperatures and conditioned volume
- Net areas and whole-assembly U/R values, plus outdoor-air ACH
- Equipment capacity at the relevant conditions; annual useful heat and seasonal COP for cost
Goal and model boundaries
Keep assembly insulation, peak heat loss, equipment capacity and annual energy assumptions consistent.
- The heat-loss calculation is a steady model, not a complete professional building-load design.
- A rated heat-pump capacity must be checked at the design outdoor temperature, including defrost/backup behavior.
Check the insulation basis
Identify whether a value describes material or a whole assembly.
U = 1/R only for the same complete layer/film basis.
- Expected output
- A documented assembly heat-transfer assumption.
- Next step
- Enter net surface areas and assembly U/R values in Heat Loss.
Estimate design heat loss
Separate exterior surfaces and enter design temperatures and effective outdoor-air ACH.
Transmission is ΣUAΔT; outdoor-air loss adds ρcpV × ACH/3600 × ΔT.
- Expected output
- Peak transmission, air loss and combined heating-load estimate.
- Next step
- Carry the known load into the equipment capacity comparison.
Compare capacity and operating cost
Use known-load mode, then a separate annual heat/seasonal-COP cost scenario.
Capacity comparison uses a stated load; annual electricity = useful heat/COP plus auxiliaries.
- Expected output
- A capacity basis and an independent annual energy/cost estimate.
- Next step
- Verify manufacturer cold-weather curves and get a project-specific load/design check.
Units and context
- Whole-assembly R differs from an insulation material-only R.
- Peak kW cannot be copied into annual kWh without an explicit time/load model.
Common mistakes to avoid
- Counting windows both as wall area and separate glazing
- Using a warm-weather rating for cold-weather heating capacity
- Confusing COP/EER with a seasonal performance guarantee