Vents & Airflow Management

Balance energy efficiency with healthy indoor air quality

CRITICAL SAFETY WARNING: Never block vents that are required for combustion appliances (furnaces, water heaters, gas stoves) or bathroom/kitchen exhaust systems. Blocking these can cause carbon monoxide buildup, moisture problems, and building code violations.

Understanding Ventilation in Your Rental

Proper ventilation is essential for health and safety. While weatherproofing helps retain heat, you must maintain adequate fresh air exchange to prevent indoor air quality issues, condensation, and potential carbon monoxide hazards.

Types of Vents: What You Can and Cannot Cover

NEVER Cover These Vents

  • Furnace intake/exhaust: Required for safe combustion
  • Water heater vents: Prevents carbon monoxide buildup
  • Gas appliance vents: Essential for safety
  • Bathroom exhaust fans: Prevents mold and moisture damage
  • Kitchen range hoods: Removes cooking fumes and moisture
  • Dryer vents: Fire hazard if blocked

May Be Adjustable

  • Floor HVAC registers: Can partially close if system allows
  • Wall HVAC registers: Adjustable louvers on many models
  • Return air grilles: Check with landlord first
  • Passive air intakes: May be seasonal (consult landlord)
Always check your lease and consult your landlord before adjusting HVAC vents.

Managing Drafts from Vents Safely

HVAC Register Adjustment

If your heating/cooling system allows, you can partially close registers in less-used rooms. However:

  • Never close more than 20-30% of your home's registers
  • Closing too many can damage your HVAC system
  • Keep bedroom registers open for comfort and safety
  • Always leave at least one register open per room

Exhaust Fan Backdrafts

Bathroom and kitchen fans can allow cold air backdrafts when not in use. Safe solutions:

  • Install a magnetic vent cover (removable, do not permanently seal)
  • Remove cover before using fan
  • Use only on rarely-used exhaust fans
  • Never cover kitchen range hoods

Window Air Conditioner Gaps

Window AC units are major draft sources in winter:

  • Remove unit if possible and allowed by lease
  • Cover exterior with weatherproof AC cover
  • Insulate gaps around unit with foam weatherstripping
  • Use indoor AC cover to block drafts through vents

Fresh Air Requirements

Even with weatherproofing, your home needs fresh air exchange. Canadian building codes and health guidelines recommend:

0.35
Air changes per hour (minimum)
15
CFM per person (recommended)

Signs of Inadequate Ventilation

  • Excessive window condensation
  • Musty odors or mold growth
  • Headaches or respiratory discomfort
  • Stuffy or stale air
  • High humidity levels (above 60%)

If you notice these signs, improve ventilation immediately by opening windows periodically or using exhaust fans.

Balance Efficiency with Safety

Proper weatherproofing reduces drafts while maintaining necessary ventilation. Learn more:

Condensation Guide Window Films Full Checklist