An HVAC Tech's Guide To Optimal ERV/HRV Settings In The Summer

When Ontario’s humid summer air starts to creep indoors, your Energy or Heat Recovery Ventilation (ERV/HRV) system becomes just as important as it is in January—only now the goal is pulling heat and moisture out, not keeping it in. Tuning your HRV for the warm season helps you stay comfortable, protects your home from mould, and can even lower cooling costs. Below is a quick guide from our in-house technicians to getting those settings right.

WHY YOUR ERV MATTERS WHEN IT’S HOT

Unlike simply opening a window, a balanced ERV exchanges stale indoor air for fresh outdoor air while controlling humidity. By removing latent heat before it enters your living space, the unit lightens the load on your air conditioner and prevents that sticky “sauna” feeling that often settles in during July thunderstorms.

OPTIMAL ERV SETTINGS FOR SUMMER COMFORT & EFFICIENCY

1. VENTILATION RATE & FAN SPEED


  • Switch to low-speed, continuous mode. Running 24/7 at a gentle speed maintains steady airflow without over-ventilating—much more energy-friendly than cycling the unit on and off, which forces the core to re-equalize every time.
  • Use high-speed “boost” only for spikes such as big family cookouts, long showers, or basement workouts.


2. HUMIDITY CONTROL

  • Target 40 – 50 % indoor RH. Health Canada notes that keeping summer humidity below 50 % limits mould and dust mite growth.
  • If your HRV includes a built-in dehumidistat, set it near 45%. Otherwise, pair a plug-in hygrometer with manual boosts whenever RH creeps above 50%.


3. BALANCE FRESH AIR WITH COOLING

  • Confirm that supply and exhaust airflows are equal. Excess incoming air can push warm drafts into upper floors, while excess exhaust can depressurize the home and draw humid air through cracks.

HOW TO ADJUST YOUR ERV/HRV CONTROLLER FOR SUMMER STEP-BY-STEP:

  • Set the Mode to Ventilation (not Recirculation).
  • Dial Fan Speed to Low/Continuous.
  • Enable Summer Defrost (if available). Some models bypass heat exchange when outdoor temps exceed ≈ 25 °C, so you’re not pushing extra heat back indoors.
  • Fine-tune the Dehumidistat to 45%.
  • Schedule Night-Time Boosts. Cooler night air lets the HRV expel built-up heat without raising indoor temperature.
  • Re-Balance After Major Weather Swings. When a heat wave breaks, double-check humidity and adjust as needed.

QUICK MAINTENANCE CHECKLIST

  • Filters: Vacuum or replace every 30–60 days; clogged filters choke airflow and cancel out savings.
  • Core Inspection: Rinse the heat-exchange core at the start of summer to remove spring pollen buildup.
  • Outdoor Hoods: Clear lint, leaves, or insect nests so the HRV can breathe freely.
  • Condensate Drain: Ensure the line isn’t blocked; standing water breeds bacteria.

Mistake

  1. Turning the ERV/HRV off during vacation
  2. High-speed 24/7
  3. Ignoring balance

Why It Hurts

  1. A closed-up house traps moisture that can swell hardwood floors and feed mould.
  2. Wastes energy and may increase humidity by dragging in more moist air than the core can remove.
  3. Imbalanced airflow can back-draft combustion appliances or suck humid attic air inside.

BREATHE EASIER ALL SUMMER WITH GUELPH CLIMATECARE

Fine-tuning an ERV or HRV isn’t complicated, but every home is unique. If you’d like expert calibration, fresh filters, or a whole-home humidity assessment, our certified technicians are ready to help. Call (519) 829-3666 or contact us for a summer comfort check-up today.