85%+
Heat recovery efficiency
MERV-13
Minimum filtration rating
<50ppm
Target indoor CO₂ above ambient
In a conventionally built home, fresh air enters through cracks, gaps, and leaky windows — an uncontrolled process that wastes energy, admits pollutants, and provides inconsistent ventilation. In a high-performance home built to 1.0 ACH or tighter, those accidental air pathways are sealed. The house needs a mechanical respiratory system — and that system is the Energy Recovery Ventilator.
An ERV is not a simple fan. It's a precision heat exchanger that simultaneously exhausts stale indoor air and draws in fresh outdoor air, transferring up to 85% of the outgoing air's thermal energy to the incoming stream. The result: continuous fresh air without the energy penalty of opening a window in January.
At Starlit Homes, ERV design is integral to every project from the earliest schematic phase. Here's the engineering that makes it work.
How an ERV Works: The Core Exchange
At the heart of every ERV is the enthalpy core — a matrix of thin membranes or plates that separate the outgoing and incoming air streams. As stale warm air exits the building, it passes through one side of the core. Fresh cold air enters through the other side. The membrane allows thermal energy and moisture to transfer between streams without mixing the air itself.
This is distinct from an HRV (Heat Recovery Ventilator), which transfers only sensible heat — temperature — but not moisture. ERVs transfer both sensible and latent heat (moisture), making them superior for Ontario's climate where winter air is extremely dry and summer air can be excessively humid.
Modern counter-flow ERV cores achieve sensible heat recovery efficiencies exceeding 90% and total (enthalpy) recovery above 80% — meaning less than 20% of the outgoing air's energy is lost.
"An ERV doesn't just ventilate — it recycles thermal energy. In a -20°C Ontario winter, an 85%-efficient ERV delivers outdoor air to the living space at approximately 14°C before any supplemental heating."
Ventilation Rates: How Much Air Do You Need?
ASHRAE Standard 62.2 defines minimum ventilation rates for residential buildings. The formula accounts for floor area and number of bedrooms:
Required CFM = 0.03 × floor area (ft²) + 7.5 × (bedrooms + 1)
For a 2,800 sq ft, 4-bedroom home:
0.03 × 2,800 + 7.5 × 5 = 84 + 37.5 = 121.5 CFM continuous
At Starlit, we design ERV systems to exceed ASHRAE 62.2 minimums by 15–20%, ensuring robust dilution of CO₂, volatile organic compounds (VOCs), and particulate matter even during high-occupancy events. Our target is to maintain indoor CO₂ levels below 800 ppm — well under the 1,000 ppm threshold where cognitive function begins to decline.
Filtration: The Second Line of Defense
Fresh air is only beneficial if it's clean air. Every ERV installation at Starlit includes a minimum MERV-13 filtration stage on the incoming air stream. MERV-13 filters capture 85%+ of particles between 1.0–3.0 microns — including pollen, mold spores, bacteria, and fine dust.
For clients with allergies, respiratory conditions, or homes near agricultural areas, we offer HEPA-grade (MERV-17+) filtration upgrades that capture 99.97% of particles at 0.3 microns. Combined with the ERV's continuous air exchange, this creates indoor air quality that rivals hospital-grade clean rooms.
This mechanical filtration approach works hand-in-hand with our radon mitigation systems — by maintaining positive pressure in the living space through balanced ERV operation, we further reduce the potential for soil gas infiltration.
Duct Design: The Often-Overlooked Variable
Even the best ERV core is compromised by poor ductwork. At Starlit, we follow the Passive House Institute's duct design principles: dedicated, insulated, sealed duct runs with minimal bends, balanced flow rates at every register, and commissioning with measured airflows at each supply and exhaust point.
We specify rigid galvanized or semi-rigid aluminum ducts — never flex duct — to minimize pressure drop and turbulence. Each bedroom receives a dedicated supply register, and exhaust points are located in bathrooms, kitchen, and laundry areas to capture moisture and pollutants at the source.
Post-installation, every system is balanced using a calibrated flow hood to ensure measured airflows match design specifications within ±10%. This commissioning step is critical — an unbalanced system can create pressure imbalances that drive moisture into wall cavities or pull soil gases through foundation cracks.
"We design the ductwork before the framing begins. In a high-performance home, the ventilation system isn't an afterthought — it's a primary structural consideration."
The Starlit ERV Specification
Standard ERV Package
- • High-efficiency counter-flow ERV core (rated for Ontario climate)
- • 90%+ sensible heat recovery, 80%+ total enthalpy recovery
- • MERV-13 supply filtration (HEPA upgrade available)
- • Dedicated rigid duct runs — no flex, no shared HVAC trunks
- • Per-room supply commissioning with documented airflow reports
- • CO₂ sensor-driven boost mode in primary living areas
- • Summer bypass mode for free cooling on mild nights
Key Takeaways
ERVs recover 85%+ of outgoing thermal energy while providing continuous fresh air exchange.
ERVs transfer both heat and moisture — superior to HRVs in Ontario's extreme seasonal humidity swings.
ASHRAE 62.2 defines minimum ventilation rates; Starlit designs exceed these by 15–20%.
MERV-13 filtration is our minimum; HEPA upgrades capture 99.97% of particles at 0.3 microns.
Duct design and commissioning are as critical as the ERV unit itself — poor ducts negate premium equipment.
CO₂-sensor boost mode ensures air quality responds dynamically to actual occupancy patterns.
