How to use the Heat Loss
Obtain coordinated room geometry, exposed-element areas, U-values, design temperatures, ventilation assumptions and weather or source references before building the model.
The workspace starts blank. Load example temporarily fills the controls with demonstration data; reload or use the tool’s New or reset action, where provided, before entering live information.
- Choose Regional context and Input / display units, then enter internal and external design temperatures, air changes, heat recovery and the Exercise title.
- Enter wall, roof, floor, window and door U-values with an Assembly/source reference.
- Add each room or zone with length, width, height, opening areas, number of external walls and any explicit thermal-bridge allowance.
- Review fabric and ventilation losses separately and use the model result to compare options, not to select final heating equipment.
Worked examples
These examples explain the set-up, expected output and review needed without changing the tool workspace.
Window retrofit comparison
- Set-up
- Duplicate an existing room model and change only window U-value and, if justified, air-change or heat-recovery assumptions.
- Result
- Compare the window fabric component and total room heat loss before and after the proposed work.
- Review
- Keep geometry and design temperatures identical and record evidence for infiltration assumptions.
Multi-room concept model
- Set-up
- Add rooms with their actual external-wall count and opening areas while sharing one stated set of design conditions.
- Result
- The output distinguishes each room contribution and the building fabric-versus-ventilation split.
- Review
- Investigate unusually dominant rooms before using the total in later engineering work.
Suggested workflow
Place the tool in a controlled project or practice process rather than treating its output as an isolated verdict.
- Fix the envelope and weather assumptions and reference their source.
- Model rooms consistently, then compare specific fabric or ventilation options one change at a time.
- Hand the coordinated geometry and assumptions to the appropriate detailed load calculation and services designer.
Check before saving or issuing
- Internal and external temperatures represent the intended design condition, not an average day.
- Opening areas are not also included in opaque wall area.
- U-values, ventilation and bridge allowances have identifiable sources and consistent units.
Common problems
- Heat loss is much too high: check temperature units, opening areas and whether wall area includes windows twice.
- Ventilation dominates unexpectedly: verify room volume, air changes and heat-recovery percentage.
- Imperial conversion looks inconsistent: confirm the original U-values and dimensions were entered under the correct unit setting.
Output
A room, zone and building heat-loss breakdown with a reproducible calculation trace.
Professional boundary
This is a concept-stage estimate, not a validated EN 12831 or Manual J calculation and must not size final heating equipment.