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Essential Guide for Dryer Vent Inspection - How to Ensure Your System is Up-to-Code

Updated: Jul 17, 2023


Home Inspectors | Dryer Vent Inspection | SafeFlow Dryer Vent Cleaning Pittsburgh PA
Dryer Vent Clogged Due to Improper Installation

Ensuring proper dryer vent installation is a vital part of the home inspection process. As an essential part of the International Residential Code's (IRC) regulations, inspectors must ensure that all dryer vents are properly installed and in compliance with safety standards. This guide will provide comprehensive advice and best practices for home inspectors to follow when checking dryer vents during an inspection. We'll discuss everything from how to identify potential issues to what should be done if something is found and needs repair or replacement. By the end, you'll have all the information you need to make sure your future inspections are up-to-code and your clients have dryers that run safely and efficiently.


Why Is Proper Dryer Vent Installation so Important?


I often encounter confusion among homeowners and realtors when it comes to choosing the correct venting material for clothes dryers. Startling statistics from the Consumer Product Safety Commission (CPSC) reveal that faulty clothes dryer vent installations cause over 15,000 house fires and nearly $100 Million in property damage each year in the US alone. Surprisingly, these fires related to clothes dryer vents are more common than most people realize, but thankfully, they can be easily prevented. Many dryer vents are incredibly dirty inside, a fact that most people are unaware of until they experience a fire or decide to finally clean out their clothes dryer vent, often years later than they should have. Let me help you understand how to avoid these risks and keep your home safe and your clothes dryer running smoothly.


How to Properly Clean Your Dryer's Lint Filter and Compartment


When it comes to clothes dryers, we all know about the lint trap filter. But did you know that the compartment housing the filter tends to accumulate lint as well? This area often goes unnoticed and neglected, but it's vital to keep it clean for optimal performance. While accessing this hard-to-reach spot can be tricky, it's usually protected by a secured cover with a few screws. Here's a handy tip: make it a habit to not only clean the lint filter after every load of laundry but also remove the lint from the surrounding area. To do this, you'll need a vacuum cleaner with a hose attachment. Simply remove the cover, and voila! Cleaning both the lint filter and the adjacent compartment is key to ensuring efficient dryer operation.


Avoid the Use of Improper Dryer Vent Materials


During a typical drying cycle, approximately a gallon of water is extracted from clothes, transforming into water vapor. To facilitate safe removal, the dryer vent system plays a crucial role in transporting this vapor, along with lint and heat, outside the house. However, it's essential to be aware of an improper type of dryer vent often found in many homes—flexible vinyl tubing. While this ribbed, white tubing seems benign, it poses a significant fire hazard due to its potential to melt. Once that happens, even a tiny spark can ignite the highly flammable lint buildup inside, resulting in a dangerous house fire. Moreover, this accumulation of lint obstructs the vent, hindering the free flow of air and causing the clothes dryer to consume more energy and take longer to dry clothes. Consequently, utility bills rise as the drying cycle extends to an excessive two or three hours. Take a look at the photo below that illustrates the vinyl (plastic) tubing commonly found in such instances. This is a picture taken at a client inspection where the vinyl tubing had melted and had been exhausting lint and moisture into the ceiling for some time before we were called to investigate and replace it.


Home Inspectors | Dryer Vent Inspection | SafeFlow Dryer Vent Cleaning Pittsburgh PA
Vinyl tubing melted, exhausting into ceiling

I often come across another type of improper dryer vent material called mylar foil tubing. It's a shiny, flexible ribbed tubing that mistakenly gets installed because it looks like metal. However, it is not approved for use as a clothes dryer vent. This material is manufactured for bathroom venting and is not designed to withstand the heat generated by dryers. Instead, it is recommended to use a UL 2158A approved material. One excellent example is a product called DryerFlex, which looks similar to mylar but is more rigid and reliable.


To determine if your transition duct is UL approved, look for a sticker that says "UL 2158A". If it doesn't have this sticker, it's best to replace it with a proper rigid metal dryer vent material. Keep in mind that the transition duct should be as short as possible, ideally no longer than 8 feet, to ensure a good connection to the metal vent.


Additionally, make sure the transition duct is not located within any wall, floor, or ceiling covering. Concealing flexible duct in walls, floors and ceilings is a violation of IRC building code. This is important because it needs to be visually inspected and easily cleaned.


Home Inspectors | Dryer Vent Inspection | SafeFlow Dryer Vent Cleaning Pittsburgh PA
Mylar foil duct cannot be concealed in ceilings, floors or walls

Occasionally, I come across situations where the mylar tubing is improperly used to vent a clothes dryer into the basement. What I would like to highlight first is that using tubing that is longer than 8' is an incorrect installation. Secondly, venting the dryer into the basement can lead to moisture being released into your home, which creates a potentially dangerous environment. This moisture can contribute to the risk of fire (due to lint) and the growth of mold. It's also important to note that this type of vent can easily get crushed which causes blockages and ventilation issues. Additionally, I've noticed installations where the vent discharges into a garage, which poses even more hazards. In this case, carbon monoxide or the risk of a garage fire can potentially enter your home through the vent. Making sure your dryer vent is properly installed and vented is crucial for the safety and well-being of your home.


I've noticed a concerning trend in newer homes where builders are using 4" PVC drain pipe as the clothes dryer duct. In fact, during a recent inspection, I discovered plastic drain pipe, typically used for downspouts, was being used as a dryer vent. It's important to note that while PVC is suitable for plumbing drain and venting purposes, it should never be used for venting a clothes dryer. Why? Well, PVC is made of plastic, which can create a static charge that can ignite dryer lint, potentially leading to a dangerous fire. Check out the image below from a recent home inspection that highlights the incorrect use of thin aluminum tubing and cloth duct tape connected to PVC pipe. It's clear that all three items (the tubing, tape, and PVC pipe) were improperly used. We need to make sure we get it right and prioritize safety every step of the way.


Home Inspectors | Dryer Vent Inspection | SafeFlow Dryer Vent Cleaning Pittsburgh PA
Never use thin aluminum, duct tape or PVC for dryer vents

The IRC (International Residential Code) section M1501 sets out requirements for the construction of clothes dryer vents. These vents should be made of rigid, smooth, galvanized metal, with a thickness of at least 0.016" (28-gauge). It's important that the interior surfaces of the vent are smooth and that no sheet metal screws extend into the duct. To ensure safety and prevent potential clogs, it's recommended to meet the UL 2158A standard for clothes dryer vents.


Sheet metal screws that penetrate the material can trap lint, leading to vent blockages over time. Check out the second photo below for an illustration. Keep in mind that a home inspection is not a code compliance inspection - the AHJ (authority having jurisdiction) is responsible for determining and verifying code compliance. However, as a reference, home inspectors follow these standards to protect their clients from potential hazards, like house fires.


Take a look at the first photo below to see the proper rigid metal duct material. You'll notice that it looks quite different from the mylar foil material, which can't be easily bent.


Home Inspectors | Dryer Vent Inspection | SafeFlow Dryer Vent Cleaning Pittsburgh PA
Smooth, rigid, metal at least 0.016" thick (28-gauge)

Dryer Vent Exhaust Terminations


To maintain optimal dryer performance and prevent unwanted elements like water, birds, insects, and cold air from entering the duct, it is essential to have a dryer ventilation system that terminates to the home's exterior with a proper dampered or louvered cover. Exterior screens on dryer vents, although prohibited by the IRC, can cause lint buildup and vent blockage over time. Fortunately, these screens can often be easily removed (and must be, according to IRC regulations for dryer vents) while leaving the dampered or louvered cover intact.

Home Inspectors | Dryer Vent Inspection | SafeFlow Dryer Vent Cleaning Pittsburgh PA
Screens must be removed from dryer vent terminations
Home Inspectors | Dryer Vent Inspection | SafeFlow Dryer Vent Cleaning Pittsburgh PA
Screens left in dryer vent terminations create lint blockage

Venting a clothes dryer inside the house, be it in the garage, basement, attic, or any other enclosed area, can result in excessive humidity, potential mold growth, and increased fire risk. Make sure the dryer vent terminates in an exterior area free from obstruction by vegetation, snow, mulch, dirt, etc., and maintains a distance of at least 3 feet from doors and windows. Avoid discharging dryer vents into covered basement window wells as well. Additionally, it's important to position the dryer vent away from air conditioning or heat pump units to prevent lint accumulation on the unit's fins, which can hinder its proper operation. Lastly, if you live in a snowy area, ensure that the dryer vent termination point remains clear of snow to minimize the risk of fire or carbon monoxide buildup.


When connecting your clothes dryer to the rigid metal duct material, it is recommended to use semi-flexible rigid metal ducting. Although this material has a slight bendability, its fire-proof design is stronger than plastic or mylar foil (slinky-style) material, cannot be easily crushed and maintains the required 4 inch size which ensures optimum performance. Take a look at the photo below to see the flexible rigid metal ducting. Notice the significant difference compared to the mylar foil ducting shown earlier in this article. If your clothes dryer and exterior vent are close together, you can often use a single piece of flexible rigid metal duct, as shown below, as the primary duct, so long as it does not pass behind any wall, floor, or ceiling covering.

Home Inspectors | Dryer Vent Inspection | SafeFlow Dryer Vent Cleaning Pittsburgh PA
UL 2158A listed, semi-rigid, metal transition hose

Proper Length for Dryer Vent Exhaust Systems


Sometimes, I come across dryer vents that are way longer than they should be - exceeding 40 feet. In such cases, it is recommended to modify or reroute the vent system to terminate in a different exterior location, closer to the laundry appliances. This way, we can have a shorter run, which is highly beneficial. IRC standards advise that clothes dryer vents should not exceed 35 feet in length, should be free of kinks, and have minimal bends. The more bends there are, the shorter the overall length should be. For every 90° bend, the vent should be shortened by 5 feet, and for every 45° bend, it should be shortened by 2.5 feet.


As part of a home inspection, it is crucial for the inspector to report the visibility, type, and condition of the clothes dryer vent, and recommend necessary modifications if any safety concerns are found. If the vent is not visible, such as when it passes through walls, ceilings, or insulation, the home buyer should ensure that a proper rigid metal vent is installed and inquire about the last time it was cleaned from the seller.


During every home inspection, it is highly recommended that the clothes dryer vent and its exterior cover be thoroughly cleaned at least once a year for preventive maintenance. This practice also serves as a reminder for homeowners to check that the vent is secure behind the dryer and at its termination point. If the dryer vent is relatively short and easily accessible, homeowners can disassemble and clean the interior using a vacuum cleaner with a long hose attachment. However, for long vents or those located within walls or ceilings, it's best to hire a professional. Professional dryer vent cleaning services use specialized tools and equipment to fully inspect the venting materials, length of the system, and ensure thorough cleaning using visual inspections with dryer vent video cameras and test for proper back pressure and air flow.


In numerous home inspections, only a small portion or even none of the clothes dryer vent is visible. This is all the more reason why it is important to hire a professional to support your inspection and ensure a thorough cleaning is completed.


Preventing house fires caused by improper or blocked dryer vents is simple, and a little preventive maintenance can make a life-saving difference. When was the last time you checked and cleared your dryer vent? Ensuring your family's safety is crucial, and I'm here to help you with that. Call Allegheny County's dryer vent specialists at SafeFlow Dryer Vent Cleaning Pittsburgh PA.


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