When installing a vented dryer, you have to follow the building codes. Not just to be code-compliant and legal but also to be safe and healthy (which is why the codes exist anyway). One crucial part of dryer installation is vent termination.
Building codes can get pretty complicated, and sometimes, it’s hard to figure out exactly what they mean by what they say. Over the years, there have been certain parts of the IRC that I have grown very familiar with, and venting is one of them. I am going to share my plain English interpretations with you here.
Venting a dryer through the roof is not explicitly prohibited or allowed by the IRC. However, it can be done if the manufacturer allows it, it’s the shortest ducting route, and the vent is not located near any openings into the home.
Roofs Are Not Mentioned in the IRC
Section M1502 of the International Residential Code (IRC) discusses dryer venting codes. However, it does not say whether or not roof venting can be used.
That means it comes down to inference or logical reading between the lines.
Basic Venting Requirements for Dryers
There are a lot of rules regarding venting dryers in the IRC. We cover these in detail in our guide on the Dryer Vent Code Requirements. For the purposes of this article, we are going to be looking at a few key points.
Do What the Manufacturer Says
While the IRC doesn’t say one way or the other whether roofs can be used for dryer vents, they do explicitly say to do what the manufacturer says.
If the manufacturer says you cannot use the roof for the vent, then the roof should not be used for the vent.
If they say that you can, then doing so will not be considered a code violation and it will be up to you to decide if this is the best option for your situation.
If the manufacturer doesn’t mention a roof vent one way or the other, then it can be assumed that venting through the roof is a possibility.
However, if you are permitted to vent through the roof, this location also has to meet all the other venting code regulations in order to be compliant. We will go through these in the next few sections.
The most likely situations will be that they don’t mention it specifically or they give it as one of the options.
The IRC defers to the manufacturer for venting criteria because the manufacturer may have designed a dryer with a particular venting scheme in mind. This venting scheme is likely the most efficient and safest way to vent that particular dryer.
Make Sure That It Vents Outside
These regulations are listed in back-to-back sections, so you can be sure this regulation is serious and quite important.
Venting via the roof leads to the outside, so a roof vent would be in compliance with this regulation.
Making sure that vents lead outside is extremely important because if they don’t, serious health and safety hazards can arise in your home.
Exhaust vents release hot and moist air, which can be damaging to the structure and finish of a house and negatively impacts the indoor air quality. It also promotes mold and mildew growth, further harming the home and homeowner.
Additionally, lint is carried in the exhaust. Lint is flammable and can create a fire risk if it settles and accumulates around the home.
Finally, gas dryers vent carbon dioxide, which is not great to fill a home with, but they can also create carbon monoxide, which, if inhaled, can be deadly. The chance of breathing in these fumes increases greatly if a vent releases these fumes inside.
Keep Away From Openings Into the House
If the manufacturer doesn’t offer specific instructions regarding where the vent should be located, the IRC offers their own instructions/directions.
Section M1502.3 of the IRC says:
“If the manufacturer’s instructions do not specify a termination location, the exhaust duct shall terminate not less than 3 feet (924 mm) in any direction from openings into buildings, including openings in ventilated soffits.”
If you are going to all the trouble of venting your dryer to the outside, you will want to keep all the exhaust outside. Placing vents near openings into the home will defeat this goal.
A dryer roof vent would be well away from most windows, doors, and mechanical intakes, but you will still need to watch out for:
- Soffit vents
- Attic vents
- Other exhaust vents (e.g., from the bathroom fan)
- Openable skylights
- Gable windows
- Plumbing vents
Choose the Shortest Ducting Route
Duct length should be decided by referring to the dryer’s manufacturer of the dryer exhaust power ventilator.
Additionally, Section M1502.4.6 of the IRC offers some regulations for dryer ducting in the absence of manufacturer guides. The ducting must be 35 ft minus a certain length per elbow or bend that occurs.
This regulation that most often excludes venting a dryer through the roof because dryers are normally located in the basement or on the ground floor of a home.
In such cases, running ductwork all the way up the house to reach the roof is definitely not the shortest path. Rather vent through the wall or even the soffit.
If the dryer is kept on an upper level of a home, then the roof becomes a more viable option. The closer the dryer is to the roof, the more reasonable using the roof for the vent is.
The shortest route is important for the effectiveness and efficiency of the dryer.
The longer the ductwork is, the less efficient it is at expelling the exhausted air because this air needs to cover more ground before leaving the ducts.
So, it is exposed to larger duct surface areas and suffers greater energy loss as a result of friction. Moreover, longer ducts are more likely to have bends and elbows, which also causes energy loss.
Benefits of Roof Venting
Dryer Vent Is out of Sight
A dryer vent on the roof is convenient because it is out of sight. Dryer vents and their covers may be considered an eyesore but this problem is pretty much completely avoided when the vent is located on the roof.
The dryer vent being on the roof also gives it a higher chance of being further away from other openings or vents leading into the house.
Exhaust Is Quickly Carried Away From the House
A dryer vent on the roof is also one of the best ways to ensure that the exhaust is quickly carried away from the house. This is because there are fewer objects or things in the way of the air being released.
A vent on the side of the house already makes the exhaust fight against its natural tendency to rise as it travels through the ducts.
But once it is released outside, wind blowing in a certain direction keeps it trapped against the side of the house.
Other obstructions like shrubs, bushes, trees, hedges, etc., are also commonly found along the sides of homes. These can also slow down the dispersion of the exhaust.
Easier to Keep Away From Neighbors’ Houses
Exhaust vents that are on the roof also have less of a chance of impacting your neighbors’ homes.
In tightly packed urban housing (downtown in cities for example), dryer vents that come out of the side of the home may be too close to a neighbor’s window, door, or any of their vents.
An exhaust vent on the roof almost certainly avoids a neighbor’s home and any potential of the exhaust fumes from your home impacting theirs.
If the neighbors have a balcony, then more consideration may need to be given when placing a dryer vent on the roof and the direction it is most likely to release the exhaust.
Drawbacks of Roof Venting
Cleaning the Duct May Be Difficult With a Roof Vent
A dryer vent being on the roof is almost definitely going to be more difficult to clean than if the vent were on the side of the house.
The IRC doesn’t say that the ducts need to be cleaned regularly, but they absolutely should be so that there isn’t a buildup of lint or potentially animals/insects attempting to live in the vents.
You will not find a dryer for which regular cleaning is not in the manufacturer’s instructions.
The reason for a roof vent being more difficult to clean is just the accessibility factor. To clean the roof vent, you will most likely need a ladder, which in itself is a hassle and creates more hoops to jump through.
A vent on the side of the house is significantly easier to access and is, thus, easier to maintain and clean.
Holes in the Roof
Holes in the roof are not very desirable.
Anytime there is a hole in the roof, the attic and the roof become exposed to increased risks. Some of these risks include water damage and animals or insects entering the home.
Even when the holes in the roof are made for vents and sealed properly, any sort of opening in the roof is going to create a higher risk for problems than if there wasn’t a hole in the roof.
Problems on a roof tend to go unnoticed longer than problems with a home’s siding, for example, because of their location. This then means that any problems that do arise have a greater chance of becoming more severe.
With holes increasing the potential for risks, and the hole being on the roof, problems caused by a vent through the roof could be devastating.
Exposed to Weathering and Weather
A dryer vent on the roof is also exposed to greater degrees of weathering.
This can be a problem for numerous reasons.
Rain may leak into the ducting, which can create mold and lead to other problems because the ducting isn’t meant to hold any amount of water.
Snow could also accumulate over the vent and block it from releasing the air it is trying to get outside of the house.
Snow buildup on the vent could also create problems with snow entering the duct. This snow may then melt due to the warm air that the vent is releasing, and more water is then present in the duct.
A vent constantly encountering water is also more likely to wear faster, which makes maintenance more difficult and replacement more likely.
The wind and sun are also weathering elements that can shorten the lifespan of the external portions of your dryer vent.
Not Viable if Roof Is an Entertainment Area
Roofs that have patios, decks, or are used as an entertaining space are not suitable to have the dryer vent through them.
This is because the vent is supposed to keep the exhausted air away from you. In addition, there is more likely to be an opening into the house located near or on the roof.