BuildMeter guide · Energy & Electrical
Heat-Recovery Ventilation Planning Guide
Plan balanced ventilation from required outdoor airflow and climate conditions. Includes measurement workflow, a worked example, decision table, ordering checkpoints, common failures and professional boundaries.
Direct answer
What to know first
Plan balanced ventilation from required outdoor airflow and climate conditions.
Open Heat Recovery Ventilator CalculatorPlan airflow and recovered heat as separate quantities
A heat-recovery ventilator (HRV) exchanges stale indoor air for outdoor air while transferring part of the temperature difference between the two air streams. The planning inputs are ventilation airflow, indoor/outdoor temperatures, sensible recovery efficiency and operating time—not packages or generic material allowance.
| Input | Meaning | Why it matters |
|---|---|---|
| Outdoor-air flow | cfm or L/s | Sets ventilation volume and fan duty |
| Temperature difference | Indoor minus outdoor temperature | Sets sensible heating/cooling load |
| Sensible recovery efficiency | Fraction of temperature load recovered | Reduces ventilation heat loss |
| Run time | Hours/day or duty cycle | Converts rate to energy |
Worked recovery example
Assume 100 cfm of outdoor air, indoor air at 70°F and outdoor air at 30°F, a 40°F temperature difference. Using the common sensible-air approximation 1.08 × cfm × ΔT, untreated ventilation would represent about 4,320 Btu/h of sensible heat. At 70% sensible recovery, roughly 3,024 Btu/h is recovered and about 1,296 Btu/h remains as ventilation heating load, before fan power and frosting/defrost effects.
Recommended workflow
- Establish the required outdoor-airflow basis for the home and local requirements.
- Use the Heat Recovery Ventilator Calculator to compare airflow, temperature difference and recovery efficiency.
- Check fan power and annual run time separately from recovered thermal energy.
- Verify duct size, balancing, intake/exhaust placement and condensate handling from the selected equipment instructions.
Common mistakes
- Using advertised maximum airflow instead of the balanced design airflow.
- Treating sensible recovery efficiency as total system efficiency in every climate condition.
- Ignoring fan electricity when comparing annual energy impact.
- Assuming an HRV replaces bathroom/range exhaust requirements or dehumidification strategy.
Professional limits
Ventilation rates, duct design, combustion safety, frost control and balancing require system-specific design and commissioning. The calculator is a planning model, not an HVAC design approval.