A Guide to Venting Gas vs. Electric Dryers

Dryers look simple on the outside: toss in damp clothes, press start, remove warm laundry. Behind that convenience is a small but serious air-movement system that must be vented correctly and—especially in modern, airtight homes—balanced with adequate make-up air. This article walks Canadian homeowners through the practical differences between gas and electric dryers, what proper venting entails, where make-up air fits in, and how to navigate code basics with confidence.

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The short version (key takeaways)

Both gas and standard electric (vented) dryers must exhaust outdoors. Never into a garage, attic, crawlspace, or interior room.
Gas dryers add combustion by-products to the exhaust. The stakes are higher for vent quality and make-up air because of carbon monoxide (CO) risk and burner performance.
Make-up air matters in tight Canadian homes. Without it, the dryer can depressurize the house, backdraft a fireplace or gas water heater, and lengthen dry times.
Codes set the floor; the manufacturer’s installation manual sets the specifics. Local bylaws and provincial rules can add requirements—always check both.
Use a smooth metal duct, keep it short and straight, and clean it regularly. This improves safety, efficiency, and fabric care.

How a dryer actually moves air

A dryer pulls room air across the wet laundry, heats it, and pushes moist air outside. Restrict that airflow—say, with a long, kinked, or lint-clogged vent—and three things happen: dry times get longer, energy use spikes, and temperatures in the dryer rise, which can stress components and fabric. Gas dryers also rely on stable airflow to burn cleanly; starved airflow can cause incomplete combustion.

Venting fundamentals (applies to both gas and electric)

Dedicated outdoor termination.
Exhaust must go directly outdoors through its own duct and cap with a backdraft damper. No sharing with a bath fan or range hood.
Duct material and size.
Use a 4-inch (100 mm) smooth metal duct (galvanized or aluminum). Avoid plastic and thin foil “accordion” flex except for the short, visible connector from dryer to wall, where allowed—and even there, a short, UL/ULC-listed semi-rigid or rigid section is better.
Shortest, straightest path.
Each 90° elbow adds substantial “equivalent length.” Fewer bends and shorter runs = stronger airflow and faster drying.
Proper termination.
Exterior hood with a gravity damper (or low-resistance louver) that opens easily and sits at least 12 inches above grade, clear of snow drift zones, screens, and nesting (don’t add insect screens; they lint up). Point away from walkways to avoid lint stains.
Sealing and support.
Seal metal-to-metal joints with foil (aluminum) tape, not cloth “duct tape.” Support long runs every 4–6 feet to prevent sags that catch lint.
Routine cleaning.
Lint builds up in the duct, hood, and lint screen housing. Clean at least annually—or more often if dry times creep up.

What’s different about a gas dryer?

Combustion products in the exhaust.
Gas dryers exhaust water vapour plus small amounts of CO and other by-products. That makes airtight ducting and outdoor termination non-negotiable. Never vent to a garage, attic, or crawlspace.
Make-up air is more critical.
The burner needs oxygen and stable pressure. A tight home with a powerful range hood or HRV/ERV imbalance can cause the dryer to struggle or nearby atmospherically vented appliances (like an older gas water heater) to backdraft.
Bonding and gas work.
Supply gas connections must be done by a qualified person (licensed gas fitter), with approved connectors and shut-off valves. If you’re changing to gas, you’ll also need a properly sized gas line and a CO alarm on the floor with sleeping areas, per local requirements.

Electric dryers: simpler but still need good venting

Standard electric (vented) dryers vent just like gas models (minus combustion by-products). Airflow quality still affects dry time and energy use.
Condensing/ventless and heat-pump dryers (more common in apartments and tight spaces) don’t require an outdoor exhaust but do require good room ventilation to handle released moisture/heat (condensing) or dehumidification water management (heat-pump). If you switch to one of these, you may cap the old vent, but keep the exterior wall sealed and insulated properly.

Make-up air: why Canadian homes need to think about it

Canadian construction has trended tighter—with air-sealing, better windows, and continuous insulation—great for comfort and energy use, but it reduces “free” infiltration. A typical dryer moves 100–200+ CFM (50–95 L/s) of air outdoors. Without a path for outdoor air to replace that, the home goes negative:

Symptoms: slow drying, whistling around doors, outside air sucking in through chimneys, furnace room doors slamming, or smells entering from attached garages.
Risks: backdrafting of atmospherically vented fireplaces or water heaters (a CO hazard), and moisture/condensation issues.

Practical solutions:

Provide a dedicated make-up air pathway sized for the dryer—this can be a passive duct with a motorized damper interlocked to the dryer, or a small mechanical make-up air unit in tight homes.
Coordinate with the HRV/ERV: many installers slightly boost supply when the dryer runs to keep the house near neutral pressure.
Keep big exhausts (e.g., range hoods) from running full tilt during drying unless make-up air is also enabled.

Code & standard basics in Canada (plain-language overview)

Always check your province/territory and municipality: jurisdictions adopt and amend the National codes on different timelines.

Gas dryers: Governed by the Natural Gas and Propane Installation Code (CSA B149) and local gas regulations. Key themes are qualified installation, proper combustion air, and safe venting.
Electrical: The Canadian Electrical Code (CSA C22.1) applies to branch circuits and receptacles (e.g., 240 V circuit for electric dryers).
Building/venting: The National Building Code of Canada (NBC) and Provincial Building Codes (e.g., OBC, BCBC) address venting to outdoors, materials/fire spread, and terminations. Some municipalities add rules about exterior terminations, distances to openings, and snow lines.
CO alarms: Many provinces require carbon monoxide alarms where fuel-burning appliances exist or in routes to sleeping areas. Install and test them regardless—it’s smart protection.

What this means for you:

Follow the manufacturer’s installation instructions to the letter (vent length charts, elbow counting, hood type).
Ensure combustion/make-up air is accounted for—especially if you have other vented gas appliances.
Pull permits where required and use licensed trades for gas and electrical work.

Vent length & elbow math (how to stay within limits)

Manufacturers publish a maximum equivalent length table based on the dryer’s blower strength and the termination hood type. You count each elbow as an extra “foot/metres” of duct. A common pattern:

4" (100 mm) smooth metal duct, one hood with a damper
90° elbow = ~5 ft (1.5 m) equivalent (some charts differ)
45° elbow = ~2.5 ft (0.75 m) equivalent

Example: If the manual allows 35 ft (10.7 m) maximum with your hood:

Two 90° elbows = 10 ft
One 45° elbow = 2.5 ft
Usable straight duct left = 35 − 12.5 = 22.5 ft (6.9 m)

Go over that, and your dryer may not move enough air—especially with a gas burner. If you must snake a long route, look into in-line dryer booster fans that are specifically listed for lint-laden air and installed per code and manufacturer specs.

Materials: what to use—and what to avoid

Best: 4" smooth rigid metal duct, metal elbows with large sweep radii, and a low-resistance exterior hood.
Acceptable for short connector: Listed semi-rigid aluminum connector between dryer and wall; keep it short and without tight kinks.
Avoid: Plastic duct, thin foil “accordion” flex hidden in walls, and screens at the exterior cap (they clog with lint).
Seal with: Foil (aluminum) tape on seams; do not use cloth duct tape.
Fire safety: Keep clearances from combustible materials per the dryer’s manual and local code.

Make-up air options in practice

Passive duct with motorized damper: Opens when the dryer runs (interlock via current sensor). Simple and effective in moderately tight homes.
Tempered make-up air unit: Brings in outdoor air and tempers it so winter comfort doesn’t suffer; useful in very tight or cold-climate homes.
HRV/ERV strategy: Slightly biased supply > exhaust during dryer operation; many modern systems support this.

A home performance contractor or HVAC designer can measure pressure and recommend the simplest compliant path.

Safety checklist (Canadian homeowner edition)

CO alarms installed and tested (replace sensors per manufacturer schedule).
Dryer level, with adequate clearance to combustibles.
Rigid or semi-rigid connector neatly routed; no crushing behind the machine.
Duct runs within the manufacturer’s equivalent length limit.
Exterior hood opens freely and isn’t buried by snow; damper swings without sticking.
Lint screen cleaned every load; vent duct and hood cleaned at least annually.
No other fuel-burning appliances backdraft when the dryer operates (match-smoke test by pros, or better: a combustion safety test).

When to bring in a pro

Gas line work or conversion to gas: hire a licensed gas fitter.
Electrical circuit upgrades: hire a licensed electrician (e.g., new 240 V receptacle).
Equivalency questions: when your duct route is long/complex, or you’re considering a booster fan or a make-up air interlock.
Signs of trouble: scorch smells, unusually hot dryer top, repeated auto-shutoffs, or CO alarm events—stop using the dryer until inspected.

FAQs

Can I vent a dryer through the roof in snowy regions?
It’s allowed with the right hood, but roof terminations see more lint accumulation and are harder to service. A short sidewall termination usually performs better in Canada—just keep it above snow lines and away from gas meters and fresh-air intakes.

Is a ventless/heat-pump dryer a “no-maintenance” option?
Not quite. You’ll still clean lint filters, sometimes secondary filters/condensers, and manage condensate. They shine in tight or multi-family spaces where outdoor venting is impractical.

Do I really need to make up air for a small condo dryer?
If it’s vented to outdoors, yes—at least ensure there’s a path for air (e.g., undercut door, transfer grille). Newer, tighter condos often rely on balanced ventilation; coordinate settings so the unit doesn’t depressurize the suite.

Your next step

If you’re planning a laundry upgrade or troubleshooting slow dry times, start with a quick vent inspection and measure your run against the manual’s allowed equivalent length. For planning help and step-by-step homeowner guidance (remember, no repair services are offered), browse the resources at Appliance Rescue, or contact us with your specific scenario—gas vs. electric, vent route sketches, and photos of your termination go a long way.

This guide is for general information in Canadian homes. Always follow your dryer manufacturer’s installation instructions, your local building and gas codes, and the advice of licensed professionals.