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Ventilation heat loss: practical guide
This guide explains how to use the Count.ie ventilation heat loss. Estimate air-change heating losses and heat-recovery benefit. Follow the inputs, method and worked example below, then compare your own scenario.
Guide written .
Open the Ventilation heat loss calculatorWhat to prepare
- Use meter readings, bills, equipment specifications and actual tariff periods where possible.
- Separate power in kW from energy in kWh and daily use from annual use.
- Identify whether efficiency, standing charges and losses are included in the chosen model.
Understand the inputs
The calculation method
Loss coefficient = 0.33 × air changes/hour × volume. Annual heat = coefficient × degree-days × 24 ÷ 1,000.
Worked example
Illustrative inputs and their result.
Example inputs
- Heated building volume (m³)
- 300
- Average air changes per hour
- 0.5
- Annual heating degree-days (K·days)
- 2200
- Effective heat recovery (%)
- 0
- Heating efficiency (%)
- 90
- Input energy price (€/kWh)
- 0.1
Calculated example result
- Annual Heat Loss KWh
- 2,613.6 kWh
- Residual Heating Cost
- €290.40
How to interpret the result
Energy consumption and money saved are different outputs. Results based on entered prices or efficiencies are scenarios, not a performance guarantee, installer quote or measured emissions assessment.
Use the same demand and time horizon for each option. Test a less favourable tariff, lower efficiency or lower use to see how sensitive the estimated saving is.
Common mistakes to avoid
- Do not count the same efficiency loss twice.
- Keep standing charges and unit charges separate when the model distinguishes them.
- Check seasonal demand, export restrictions and tariff assumptions before extrapolating.
Assumptions and sources
Air changes and recovery are editable estimates. Excludes fan electricity, bypass and defrost effects, demand control and infiltration interactions.
If your case falls outside this scope, use a more suitable calculator or contact us about an unclear method.