Is an indoor dryer vent a good idea?

Having an indoor dryer vent may seem convenient, but it can lead to some serious issues. Indoor dryer vents do not effectively remove moisture and lint from the air like an outdoor vent does. Over time, this can create moisture damage and mold growth in the home, clogged ducts, and a fire hazard. While they may be tempting for some homeowners, indoor dryer vents usually cause more problems than they solve.

Why are indoor dryer vents problematic?

There are a few key reasons why indoor dryer vents tend to be problematic:

• They recirculate moist air back into the home – Outdoor vents expel hot, moist air from the dryer outside. Indoor vents recirculate that air back into the home’s environment. All that moisture can lead to mold growth, promote allergies, and damage finishes/structures in the home over time.
• They do not exhaust lint effectively – Lint screens trap some lint, but not all. The powerful air flow of an outdoor vent is needed to remove lint from the air. Indoor vents allow lint to accumulate in ducts and the indoor air.
• They increase the risk of fire – Lint buildup in ducts is highly flammable. Indoor vents allow more lint accumulation than outdoor vents, increasing fire risk.
• They are against code – Most building codes prohibit indoor dryer vents due to the risks posed.

While indoor dryer vents seem like an easy solution, the lack of proper ventilation causes big problems. Unless a high-quality filtration system is added, indoor dryer vents do not ventilate as effectively as outdoor vents.

What are the hazards of excessive indoor moisture?

The moisture from indoor dryer vents contributes to several hazards, including:

• Mold growth – Mold spores thrive in damp environments. Allowing a dryer to dump moisture into the indoor air constantly creates an ideal environment for mold to grow in walls, under floors, etc. This can contribute to allergies and respiratory issues.
• Bacteria growth – Dampness also allows bacteria like salmonella and E. coli to thrive. These can cause illnesses through contact or by spreading into the air.
• Damage to structures – Constant moisture can warp wood framing and trim, cause drywall to deteriorate, and damage household items through mildew damage and condensation.
• Damage to finishes – Moisture encourages mold growth on furniture, carpets, curtains, and more. It also leads to peeling paint and wallpaper over time.

Left unchecked, excessive indoor moisture can literally rot a home from the inside out. An indoor dryer vent adds a steady stream of moisture to an environment that is likely already humid.

What are the fire risks of indoor dryer vents?

Indoor dryer vents come with several fire hazards, including:

• Lint accumulation – Lint can build up in ducts over time, creating a flammable tinderbox inside the walls of the home.
• Reduced airflow – As lint accumulates, it restricts airflow. This can cause overheating of the dryer or ducts.
• Combustion – The combination of restricted airflow, excess lint, and high heat increases the chances of combustion inside the ducts.
• Difficult detection – Duct fires inside walls make detection and suppression difficult before serious damage is done.

The CPSC estimates that over 15,500 dryer fires occur each year in the U.S., resulting in an average of 51 deaths, 380 injuries, and $236 million in property loss. Indoor dryer vents significantly contribute to these risks. The lack of a proper exhaust vent allows lint to accumulate, restricts airflow, and recirculates heat. This creates an invisible fire hazard inside walls and ducts.

How much does an indoor dryer vent installation cost?

Installing an indoor dryer vent costs $200 to $500 on average. The exact cost depends on factors like:

• Vent type – Ducting, wall caps, terminations, etc.
• Length of venting required
• Difficulty accessing install site
• Need for structural modifications
• Labor rates in your area

Short, straight duct runs are cheapest. Long ducts that require navigating framing members or adding access hatches increase cost. Installation labor typically accounts for 50-70% of the total project cost.

Cost to install an indoor dryer vent

Vent type	Average cost
Short metal ducting	$200 – $300
Long or flexible metal ducting	$300 – $500
Through-wall vent kit	$350 – $450

Keep in mind that a poor quality indoor vent is likely to cause problems that will cost much more than installation. Investing in a higher quality vent reduces risks but does not eliminate them entirely.

What are code requirements for dryer vents?

Most building codes do not allow indoor dryer vents, with very few exceptions. Code requirements include:

• Vents must terminate outside the building.
• Vents should be as short and straight as possible.
• Vents must have a backdraft damper.
• Vents should be made of smooth metal ducting only.
• Ducts must not be fastened with screws or nails that extend into the duct.
• Maximum length should not exceed 35 feet.
• Ducts must not be crushed or kinked.
• Indoor vents require an interlock switch to deactivate dryer when filters are missing.

Some local codes may prohibit any indoor dryer vents at all. Others make exceptions for existing multi-family buildings where venting outdoors is impossible. In these cases, strict makeup air requirements (around 200 sq.ft.) and filtration systems are usually mandated. But even then, indoor venting is highly discouraged due to fire and moisture risks.

International Residential Code dryer vent requirements

Vent Criteria	Requirement
Termination location	Outdoors
Maximum length	35 feet
Duct material	Smooth metal
Duct joints	In direction of airflow
Duct supports	Every 12 feet
Backdraft damper	Required

Very few situations meet the criteria for a code-approved indoor dryer vent. In most cases, a vent terminating outside is required according to code.

Should you remove an existing indoor vent?

If your home currently has an indoor dryer vent, it’s highly recommended you remove it and install a proper outdoor vent. Leaving an indoor vent in place risks:

• Moisture damage
• Mold growth
• Higher energy bills
• Lint buildup
• Reduced dryer lifespan
• Dryer fires

Removing an existing indoor vent and routing the ducting outside can cost $500 to $1,000. While not inexpensive, this investment can prevent extensive repairs and safety hazards down the road. When contracting the work, be sure the existing duct is thoroughly cleaned of any built-up lint before re-routing it outdoors.

What are the alternatives to indoor dryer vents?

Instead of using an indoor dryer vent, consider these safer alternatives:

• Dedicated outdoor vent – Install a new vent that routes ductwork directly from the dryer to the outdoors. This is ideal, as it minimizes lint buildup and provides maximum airflow.
• Window vent kit – These kit provide a quick way to vent a dryer by fitting into a slightly open window panel. Not ideal, but safer than indoor venting.
• Condensing dryer – Condensing dryers use a closed-loop system to cool exhaust internally, then drain and evaporate residual moisture. No outdoor vent needed.
• Ventless (ductless) dryer – Ventless dryers filter lint and vent moisture into the room. Consider only if condensing dryers are not an option.
• Laundromat – For apartment buildings where venting is impossible, using a local laundromat may be the safest option.

Installing a proper outdoor vent is always the best solution. But in cases where that is impossible, the alternatives above are safer than using an indoor dryer vent.

Can you vent a dryer into a chimney?

Venting a dryer into an existing chimney or flue is sometimes presented as a solution. However, it is not recommended. Venting a dryer into a chimney has risks including:

• Increased fire risk if lint or blockages occur
• Moisture damage to chimney and roof
• Harmful gases released into the home
• Poor venting performance
• Violation of building code requirements

Most building codes prohibit venting dryers into existing chimneys or flues. The moisture, lint, and airflow can damage the chimney and reduce its ability to safely vent combustion gases. The joints are also not designed to withstand the air pressure from dryers. Ducting the dryer outdoors is the only recommended approach.

Conclusion

Indoor dryer vents may seem like a convenient solution, but in most cases they should be avoided. The lack of proper exhaust ventilation allows hazardous levels of moisture, lint, and heat to accumulate indoors. This leads to increased risk of property damage, mold growth, breathing difficulties, and dryer fires. Installing an indoor dryer vent also frequently violates building code.

There are alternatives that allow indoor drying without the risks of venting indoors. But whenever possible, installing a dedicated outdoor vent for the dryer is recommended. This provides the safest and most effective means of managing moisture, lint, and heat. Investing in properly routing your dryer ducting can prevent extensive home repairs, health hazards, and safety issues in the long run.