- Homes built or renovated after 2010 to current energy codes may be tight enough to require mechanical ventilation under ASHRAE 62.2 standards.
- ERVs transfer both heat and moisture — preferred for humid climates and summer cooling seasons across the North Shore.
- HRVs transfer heat only — preferred in very cold climates where winter moisture control is a primary concern.
New construction or major renovation in Lake or Cook County
Modern construction to current energy codes — upgraded insulation, air sealing, and high-performance windows — dramatically reduces natural infiltration. Mechanical ventilation is required by code in very tight buildings and is best practice for any new construction that achieves ACH50 below 5.0 on a blower door test.
Elevated CO₂, persistent odors, or humidity build-up in a newer home
CO₂ above 1,000 ppm in occupied spaces indicates inadequate fresh air supply. Persistent cooking odors, bathroom humidity that doesn't clear, and guests complaining of stuffiness are behavioral indicators. An IAQ test or blower door test confirms whether ventilation is the root cause.
How ERVs and HRVs work — the core exchange mechanism
Both systems pass incoming fresh air and outgoing stale air through a heat exchanger core, transferring thermal energy between the two streams. ERV cores also transfer moisture — incoming humid summer air is partially dried before entering; dry winter exhaust air is re-moisturized before venting. The two air streams never mix, preventing cross-contamination.
Integration with existing ductwork or standalone installation
ERVs and HRVs can connect to the existing forced-air distribution system or operate with dedicated supply and exhaust ducts. Standalone systems are more controllable but require a separate duct run; integrated systems leverage existing ductwork but require proper damper configuration to prevent short-circuiting.
ERV core icing in very cold weather reduces effectiveness
ERV cores can frost in very cold weather when indoor humidity is high and outdoor temperatures are below −10 °F. Quality ERVs include defrost cycles that temporarily pause fresh air intake to melt frost. Ensuring the defrost cycle is functional is part of seasonal inspection.
Unbalanced supply and exhaust creates pressure problems
An ERV or HRV that supplies more air than it exhausts — or vice versa — creates positive or negative pressure in the home that drives infiltration or exfiltration through unintended paths. Airflow commissioning and balancing after installation is required for proper performance.
Questions homeowners ask
- Do I need mechanical ventilation if my home already has bathroom exhaust fans?
- Bathroom exhaust fans remove humidity locally but aren't designed for whole-home fresh air supply. ASHRAE 62.2 requires continuous or intermittent whole-home ventilation at a rate based on floor area and number of bedrooms — point-source exhaust fans don't fulfill this requirement in tight homes.
- Will an ERV make my home feel drafty?
- A properly designed ERV introduces fresh air at low velocity through diffusers distributed across the home — perceptible as improved air quality rather than a draft. The incoming air is preconditioned to within a few degrees of indoor temperature by the heat exchange core.
- Does Legendary install ERV and HRV systems in existing homes?
- Yes — Legendary installs both systems in existing construction, integrating with the HVAC system or using dedicated ducting. The flat-rate assessment includes a ventilation rate calculation for your specific floor area and occupancy.
Editorial provenance
Content by Legendary Service editorial team
Updated:
Methodology
Guidance compares the stated system factors, applicable utility program rules, and the conditions that must be confirmed in the home. Figures are planning ranges, not quotes; Legendary Service provides an upfront flat-rate price after diagnosis.