Why mechanical ventilation matters in tight, energy‑efficient homes
Modern airtight, energy‑efficient homes stop the uncontrolled air leakage that used to dilute indoor pollutants; intentional whole‑house mechanical ventilation is required to maintain acceptable indoor air quality and meet codes and standards for these tight buildings.[4][1][3]
HRV vs ERV — what each device does
HRV (heat recovery ventilator)
An HRV transfers sensible heat only (heat without moisture transfer), providing balanced supply and exhaust while recovering heat to reduce heating load. HRVs are commonly recommended in cold, dry climates where bringing in outdoor moisture is undesirable.[6][7][5]
ERV (energy/enthalpy recovery ventilator)
An ERV transfers both sensible heat and some moisture (latent energy) between supply and exhaust streams, which helps control indoor humidity as well as temperature. ERVs are commonly recommended in mixed or humid climates to limit indoor moisture gain from humid outdoor air.[6][7][5]
There is no universal rule that fits every house; the best choice depends on climate, indoor moisture generation, overall HVAC strategy, and occupant preferences.[6][7][5]
Sizing: use ASHRAE 62.2 to pick a design airflow
Use ASHRAE Standard 62.2 to determine the continuous whole‑house ventilation target. The commonly used simplified continuous formula is:
Qfan (cfm) = 0.01 × conditioned floor area (ft²) + 7.5 × (number of bedrooms + 1).[1][12]
Example: a 2,000 ft², 3‑bedroom house → Qfan = 0.01×2000 + 7.5×(3+1) = 20 + 30 = 50 cfm continuous.[1][12]
This Qfan is the minimum design target you should meet or exceed with the installed system; use it as the basis for selecting a unit and for commissioning.
Selecting and sizing a unit for real installed performance
Determine Qfan from ASHRAE 62.2 (step above) and treat it as the required continuous flow.[1][12]
Choose a unit whose rated continuous airflow at the expected external static pressure meets or exceeds Qfan. Account for duct pressure losses, filters, and any accessories by reviewing manufacturer performance curves or selecting a slightly larger model to ensure installed flow is sufficient.[8][9][12]
Include commissioning and balancing (measure and adjust flows) to verify supply equals exhaust and that the installed system actually delivers the required continuous CFM.[1][3]
Manufacturers publish performance curves and example models to guide selection; for instance, Zehnder publishes ComfoAir performance/spec sheets and Panasonic publishes Intelli‑Balance product ranges—use those pages for model‑specific capacity, efficiency, ECM motors, frost modes, and installed‑performance curves.[8][9]
Installation best practices
Install the unit indoors in an accessible mechanical space per manufacturer instructions; provide exterior supply and exhaust terminations with weatherhoods and back‑draft protection, follow clearances, condensate drainage, and frost‑control guidance in the product documentation.[8][9]
Design ducts to minimize long, undersized, or convoluted flexible runs that increase pressure loss; include dedicated ducts for required exhaust sources (bathrooms, kitchens) as required by ASHRAE 62.2 and code guidance. For guidance on routing and termination of bathroom exhaust, see our piece on how to vent a bathroom fan correctly.[1][3]
Include controls and hardware needed for balancing (dampers, factory controls, or commissioning tools) and perform a post‑install airflow test to confirm the continuous CFM meets ASHRAE 62.2 requirements.[1][3]
Cold‑climate installs should use units or strategies with frost protection (preheat, bypass, recirculation, or electric preheaters) to prevent core icing and loss of performance; consult the manufacturer for the unit's frost‑control features and required clearances/drainage.[8][9][6]
Indoor air quality and safety considerations
Mechanical ventilation lowers indoor concentrations of pollutants (VOCs, CO₂, moisture, odors) but must be paired with source control, filtration, and combustion‑safety checks—ventilation is one part of an overall IAQ strategy.[4]
If combustion appliances are present, ensure the whole‑house ventilation plan does not create depressurization that could cause back‑drafting. Coordinate ventilation rates and commissioning with combustion appliance venting checks as part of safety testing.[3][4]
Costs and budgeting
Installed costs vary widely with unit choice, ductwork complexity, labor, electrical work, exterior terminations, and commissioning. Consumer and installer guides report typical installed totals ranging from lower‑thousand‑dollar simple installs to several‑thousand dollars for higher‑complexity jobs—get itemized bids (unit, ducts, electrical, balancing) and check for local incentives or rebates when comparing options.[11][10][5]
Commissioning checklist (installers and homeowners)
Confirm Qfan per ASHRAE 62.2 and set the unit for continuous operation at that flow.[1]
Measure supply and exhaust flows with a calibrated flow hood or manometer and adjust dampers or controls so supply ≈ exhaust and total flow meets or exceeds Qfan.[1][3]
Verify exterior terminations are installed with weatherhoods and back‑draft protection; check condensate routing and frost‑control operation per the manufacturer.[8][9]
Document operating fan speed/setting that achieves required flow and leave clear operating/maintenance instructions and filter access for the homeowner.
When to consult a pro
Hire an experienced HVAC or ventilation contractor for duct design, electrical work, and commissioning if you lack the tools or experience to measure and balance flows. For houses with combustion appliances or complex HVAC interactions, coordinate installation with combustion‑safety testing and a qualified technician.[3][4]
Quick recap
Use ASHRAE 62.2 to set continuous Qfan (formula and example above).[1][12]
Pick an HRV in cold, dry climates and an ERV in mixed/humid climates unless specific indoor moisture needs or HVAC strategies suggest otherwise; consult device specs for performance curves and frost features.[5][6][7]
Account for duct losses, filters, and static pressure when selecting a unit; commission the installed system to confirm required continuous CFM.[8][9][1]