Dryer Vent Installation: Are Indoor Dryer Vents Up To Code?

It’s estimated that over 56% of households own dryers. Some are said to dry as many as 9 loads of laundry in a given week. So, if the service of a dryer is this crucial, then it becomes necessary that the venting meets the safety requirements. The problem arises when a dryer is added where none existed, and there’s no way to vent the dryer. This lead to the creation of indoor dryer vents.

According to building codes, dryers are required to vent to the exterior. While indoor dryer vents are sold in stores, contractors and home inspectors generally consider indoor dryer venting problematic because they do not supply exterior venting for warm, moist air that can cause moisture problems and mold growth.

Traditionally, dryers were meant to blow this hot vapor outside of the home through the wall. Still, it has now become an exception with households without direct access to an outer wall to blow this air right back inside their residences. 

Indoor Dryer Vents Versus Safety

Clothes dryers are powered up by either electricity or gas burners. And because the entire drying process is contained indoors, the use of electric heating is most recommended over the use of gas. 

Exhaust from gas dryers must be vented outside as they contain carbon monoxide, which is poisonous to humans.

Some people underestimate the importance of a vent to a clothes dryer. 

You might assume that its job is to expel hot air out of the dryer and possibly out of the home, forgetting that along with the heated water vapor, the exhaust duct carries with it highly flammable cloth particles that are mostly made of cotton and polyester. 

If not frequently and adequately cleaned, lint could accumulate inside the vent, restricting heat through the vent, causing the dryer to overheat. 

Too much heat energy could cause a mechanical malfunction triggering a spark. The lint acts up and bursts into flames concurrently, causing a massive inferno. 

According to the Consumer Product Safety Commission, house fires caused by cloth dryers are more common than people care to admit and are consequently responsible for several injuries, deaths, and substantial damage to property damage property.

Indoor Dryer Venting Kits

While an electric dryer doesn’t necessarily require venting, dryer ventilation helps the appliance to be more efficient, helps collect lint and a stream for proper airflow. Failure to install one will cause the machine to be inefficient, contribute to faster wear and unregulated power surge. 

Most indoor dryer vents installments come in kits and mostly DO IT YOURSELF (DIY) projects. However, as many do not have options and choose to install them on their premises, indoor vents remain a topic full of controversy.

An indoor dryer vent kit can vent an electric clothing dryer when outdoor venting is not possible. 

Typically, the kit consists of a lint bucket, a 4” thick 5ft long flexible aluminum duct, and a clamp. In this type of system, exhaust from the dryer flows to a bucket full of water to trap the lint (filtration method) then the humid air blows into the laundry room through holes in the bucket lid.

However, the maintenance aspect is largely exhausting to many users because one has to stand on guard and keep changing the water trapping lint in the bucket until the drying cycle is completed. 

Aside from physical exhaustion, owning a system that requires frequent replacement filters could make indoor venting more costly at the end of the day.

The International Residential Code

The International Residential Code (IRC) SECTION M1502 of the CLOTHES DRYER EXHAUST is mainly concerned about the following;

Why Home Inspections Are Important x
Why Home Inspections Are Important
  1. Duct Construction
  2. Duct Length
  3. Duct Termination
  4. Duct Size
  5. Transition Ducts
  6. Duct Installation

Duct Construction

The International Residential Code requires that exhaust ducts be constructed using rigid metal ducts with flexible connectors and 4” wide.

The duct should have a smooth interior surface, and its joints should run in the direction of the airflow to allow maximum airflow. Exhauster ducts should not be connected with sheet metal screws or any other fastenings which extend into the duct.

Ducting in unfinished areas, such as attics, basements, and crawl spaces, requires 4″ metal vent piping. Flex piping is only suitable for connecting the dryer to the metal vent pipe and should not extend more than 8 feet.

Dryer vents constructed using plastic pipes are extremely dangerous. The heat level emanated by the dryer machine could ignite a fire or cause a meltdown.

Note: Actually, the smooth interior is an excellent recommendation. It causes air to flow smoothly, unlike rough interiors that act as speed bumps engaging the drying machine to use more energy.

Duct Length

The international code also clearly highlights clothes dryer ducts shall not exceed the maximum length of 35 feet starting from where the dryer is located to the termination end, which could be the wall or the rooftop excluding the transition duct.

They should be as straight as possible right from the start to the end. Turns and bends interrupt the flow of air and could become a catchment area for lint.

During Installation, exhaust ducts are supported at intervals of 12 feet each or less and firmly secured. The insert end of the duct extends into the adjoining duct, fitting toward the direction of airflow.

The only two possible exceptions by The International Residential Code, in this case, could be where a manufacturer permits a more extended exhaust vent and the incorporation of large radius bends that have undergone engineering calculations and are certified to be safe to install and use.

Duct Termination

It is recommended that clothes dryer vents are required to terminate air fumes outside the building and not less than 3feet in any direction of openings leading into buildings.

Inspectors have witnessed many defective installations during inspection visits where dryer vents empty moist air into attics and crawl spaces, encouraging wood decay and mold.

But there are certain exceptions like indoor cloth dryer vents where a buyer is recommended to meet the manufacturer’s requirements and instructions.

Duct Size

The diameter of the exhaust duct shall be as required by the dryer’s listing and going by the manufacturer’s installation instructions. This information is available on the data plate.

Transition Ducts

These are the ducts that connect the machine to the exhaust duct system on the wall.

These transition ducts should be flexible and are not to be concealed but remain in the open. These transition ducts are limited to single lengths not exceeding 8 feet. Most indoor dryer vent transition ducts are 5 feet in length.

Duct Installation

Dryer venting to the exterior is required. As stated earlier, venting should not extend farther than 35 feet from the dryer. The venting must be 4″ rigid metal piping with a smooth interior surface, with as few bends as possible. Venting to the exterior is allowed through a side wall or roof. Dryers can not vent to a soffit.

Advantages and Disadvantages of Indoor Dryer Venting Systems

The indoor dryer vents system does save not meet the above requirements. 

But when one lives in a closed-up condominium or apartment and does not have the luxury to choose from a better venting system, they do not have an option but to settle for one. 

The advantage of the indoor dryer vent, as much as it’s surrounded by controversy, is that it gets the job done.

The challenge is finding a suitable vending kit that will meet your needs.

For you to find the right indoor clothes dryer vent that will work, it is best to consider the following;

  1. Type of dryer considering its heating system.
  2. Access to a sink
  3. Are your washer and dryer stacked up or separate

The three will determine what type of filtration to go. For example, easy access to a sink calls for a water filtration system.

Indoor venting kits are mostly safe when used with electric dryers and never with gas burners. 

Examples of suitable recommendable kits that work well by using water to trap lint and generally improving the quality of air in the house are;

  1. Dundas Jafine’s Proflex Dryer Duct System.
  1. BetterVent’s Indoor Vent kit. (See Video Below)

As we consider the options of a cloth dryer, we must also admit that there is no appliance without its pros and cons and an indoor dryer vent is no exception. 

Let us look into both sides to this type of vent;


  1. During the coldest seasons, the hot vapor expelled into the room during the drying process warms up the interior making the cold less bearable. As it warms up your home, the need to turn on the heating system reduces; therefore, your household bills are reduced in a way.
  1. Generally, venting systems are known to harm the environment through pollution. For example, gas burners can power dryers up, emitting carbon monoxide to the environment. But because indoor dryers only use electricity with very few polluting elements, they become less harmful to the environment.
  1. It is an expensive modern world we live in, and everyone would welcome the reduction of household expenditure as much as possible. However, most indoor dryer vents are DIY kits and made out of readily available materials. Therefore, the amount you incur becomes way less compared to the cost of installing an outdoor venting system.


  1. Laundry rooms are rather small spaces, and the humid temperatures created could last longer. However, for every load of laundry one dries, up to a gallon full of water goes up in moist vapor; therefore, you run the risk of having a sauna-like environment within your home.
  1. In the same breath, too much moisture prevailing in the air could cause health issues like allergies and asthma. The walls and ceiling will trap the water in the air and create an environment for mold and other microorganisms to become a health hazard. The extra moisture will as well ruin wooden storage cabinets.
  1. The dryer vent filters are not foolproof and still run the risk of lint accumulating in all the wrong places, amounting to a safety hazard.
  1. The maintenance part of the kit is quiet on the high as it requires one to manually and frequently change the water in the bucket, which can prove to be tedious.
  1. The presence of lint is evidence of your clothes wearing off. Therefore, if you choose to air dry your clothes instead of machine drying, you will preserve them and spend less on replacement.

Salvage the situation and create a healthy environment for your family. It is mainly advised that it is crucial to keep all ventilations like doors and windows open to help air the room and circulate the humid air during the drying circle.

Better still, one can connect a venting hose pipe to run from the dryer up an open window or door leading to the house’s exterior. But, of course, it is not a permanent solution, therefore not requiring permanent venting lines.

Note: On regular occasions, make sure to have a filtration method and its replacement on standby. And for you not to run into trouble, first check if your locality regulations on the building code allow dryers to be vented indoors.

Dryer Vent Ducting Types

There are five types of dryer vent ducting types.

  1. Flexible Aluminum Foil Duct
  2. Semi-Rigid Metal Duct
  3. Slim Duct
  4. Rigid Metal Duct
  5. Plastic or Vinyl Duct

The flexible aluminum foil is commonly used among them. But, unfortunately, many households are oblivious of the importance cloth dryer vents play in their homes’ safety and lives.

Aside from removing the hot, moist air from the dryer, the venting systems are meant to safely carry lint past the lint filter and deposit it into the bucket full of water.

For the clothes dryer venting system to work efficiently, it should be cleaned regularly to prevent fires and mold-related problems.

They will even go a long way in terms of wear and tear, and it is solely the owner’s responsibility to make sure that their venting system is constructed from recommended materials and installed per the required code.

In general, a safety inspection officer will only be able to pinpoint issues on the system that need correcting because he will not know the manufacturer’s specific recommendations, the local code requirements, or confirm the dryer vent compliance.

Warning Signs That Your Dryer Venting Needs Cleaning

  1. The recommended drying time for an average size load of clothes is between 35 to 40 minutes and shouldn’t extend beyond 60 to 75 minutes. If it’s taking longer than that, your dyer venting may need to be cleaned.
  1. Vent hood flaps do not open properly. It could be built up of lint clogging up the vent.
  1. Lint and debris are expected. However, over time, lint and debris accumulate around the dryers’ lint filter. You should clean your lint filter each dryer run.
  1. Another one is that when you start feeling the heat temperatures in the room rise even when the dryer is running, you should be aware that lint build-up might have occurred, interfering with airflow.


Indoor dryers need to be vented to the exterior. If you must use an indoor dryer vent kit, be sure to examine and clean it regularly to prevent moisture and mold problems that will come if neglected. If you’re using an indoor dryer vent on the interior of your home or inside a basement, consider using a dehumidifier.

A dehumidifier will help collect the warm moist air from the indoor dryer vent, remove the moisture, and discharge the water into an internal bin or through a drainage tube into a sink.

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Hubert Miles

I've been conducting home inspections for 17 years. I'm a licensed Home Inspector, Certified Master Inspector (CMI), and FHA 203k Consultant. I started HomeInspectionInsider.com to help people better understand the home inspection process and answer questions about homeownership and home maintenance.

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