How to Install and Clean a Roof Dryer Vent

roof dryer vent

There are some building codes to consider when installing or cleaning a roof dryer vent. According to the International Residential Code requirements on the venting duct length, a venting duct should not exceed the maximum length of 35 feet starting from where the dryer is to the termination end, which could be the wall or the roof.

According to building codes, dryers must vent to the exterior. For dryer safety and efficiency, you should use the shortest and straightest ducting route to the outside. When dryers are on interior walls with no direct way to the exterior, they can vent through the roof.

Dryers venting through the roof need rigid metal ducting that extends straight to the roof exterior. Venting through the roof requires routine professional cleanings or the risk of lint build-up becoming a fire hazard.

The code reiterates that the venting duct should be as straight as possible from the start to the end. Turns and bends interrupt the airflow and could become potential catchment areas for lint.

Demystifying Dryer Roof Venting

It is common for households with slab foundations to vent their dryers through the roof. Though it is not popular with some contractors, builders, home inspectors, and vent cleaning technicians, this type of venting are commonplace in modern-day construction.

In the past, homeowners and venting system manufacturers focused more on getting the job done. Still, homeowners and constructors are more concerned about home beautification and greater efficiency, forcing vent duct manufacturers to up their game in today’s world.

Several scenarios can make a roof venting system the ultimate choice;

  1. The proximity to other homes – such as in townhomes where buildings are adjoined
  2. No other direct access to the exterior – such as laundry rooms on interior walls in slab foundations
  3. Aesthetics – where the venting affects building appearance or curb appeal
  4. Length of the duct – where the roof is the shortest route to the exterior
  5. Animal and rodent invasion – dryer vents low to the ground can be nesting locations for birds or be damaged by rodents
  6. Damage – children or pets can damage dryer vents low to the ground
NACHI roof dryer vent diagram

The Proximity of Other Homes

Proximity to the neighboring homes is born out of urbanization; the more people, the lesser space. Therefore, it has forced homeowners and contractors to make the best of available space.

Most often, you will find that modern homes do not have the luxury of a separate private compound. Wall ventilation becomes a little bit complicated near a building entrance or ventilation. The international code dictates that the venting duct terminates not less than three feet away from any direction.

No Other Direct Access To The Exterior

Concrete slab foundations are becoming the norm in building construction. When a dryer is along an interior wall in a concrete slab home, there is no access under the slab to run a dryer vent to the exterior. Directing a dryer to the roof becomes the only feasible option to vent the dryer outside.

Building codes say dryer vents can’t vent to a soffit, leaving the roof the only option. Dryers venting through the roof must have a rigid metal vent pipe and requires routine cleanings to prevent dryer fires. It would be best to have the roof dryer vent professional cleanings annually or as needed.

Aesthetics

Modern homes are keen on both style and beauty

No one wants vents protruding from a wall and attracting attention. And because a roof vent duct stands at less than 5 1/2 inches above the roofing slope, it’s a low profile with minimal visibility.

Any homeowner considering beauty and visibility will probably go for roof dryer vents.

Length Of The Duct

As much as the International Housing Code recommends a 35-foot maximum length, several scenarios can prove that the shorter the run, the better the outcome.

From saving you the cost and hassle of a long run to complications in maintenance, shorter runs will save you your money.

Longer runs require more energy. As heated moisture flows along a lengthy run, it may encounter friction and sometimes run into bends (if there are any) that act as speed bumps. As a result, the inside flow will be interrupted and need more energy to pick up speed.

When the runs are shorter, the duct will probably run straight. 

Straight shorter runs minimize the chances of lint build-up and dryer overheating, translating to lower chances of a roof dryer vent fire.

Animal and Rodent Invasion

Many small animals and reptiles live outside our homes and thrive on the grass and gardens in rural or urban settings. Rats, lizards, and mosquitos, among others, will quickly find entry into the homes’ interior through the piping duct.

Birds also love to nest inside dryer vent pipes which can clog the vent and restrict airflow, causing your clothes not to dry correctly and increasing fire risk.

Damage

Because wall venting systems are easily accessible, children playing outdoors and even animals might get curious, resulting in a damaged duct.

roof dryer vent

What to Consider Before Installing a Dryer Vent Through a Roof

Aside from the International Residential Code endorsing roof venting as a safe way of terminating moisture resulting from cloth dryers, there are also other organizations whose verdict plays a relevant role in the adoption and consumption of household dryer venting products;

  1. Building Code
  2. Certified dryer exhaust technicians
  3. Appliance Manufacturers

Local Building Codes

The International Residential Code and The International Mechanical Code unanimously state that dryer vents should terminate the moist water vapor on the home’s exterior.

Regardless of the termination location, a roof dryer vent meets the building code requirements as long as the termination duct has no screen feature and contains a backdraft damper.

Dryers can’t vent to a soffit.

Certified Dryer Exhaust Technicians

In their books, the Certified Dryer Exhaust Technicians union does not recommend a venting location over another. Still, it does stress the need to have shorter runs built from rigid pipes and the importance of minimizing elbows and bends. 

They also revised their notes on re-routing the venting system through the roof or the wall.

Appliance Manufacturers

All products and appliances come with a manual containing specific instructions while installing the product.

They also contain the specifications of the product. If you peruse through many dryer vent manuals, you will see that they have recommendations on roof installations.

Can a Dryer Vent Terminate Through the Roof? 

While it isn’t advisable, you can have the termination of your dryer vent going through the roof. However, venting through the roof should only be used as a last resort when running your dryer vent pipe.

The vent cap that you’ll have to put on the end of your dryer vent has the potential to block the dryer lint. Lint piling up in your dryer vent is a fire hazard, which is the number one reason why you should pursue other options for venting your dryer. 

Here are several of the main reasons why you shouldn’t vent your dryer through the roof:

Fire Hazard 

As I just mentioned, dryer vents terminating through the roof present a more significant fire hazard than vents going through the side of a wall. The dryer vent pipe is responsible for expelling hot air and moisture along with dryer lint away from the dryer. If the line is vented vertically through the roof, the type of vent cap that you must use presents more of a blockage hazard than other caps do. 

Risk of Water Damage 

While roof dryer vents have special rain caps installed, they aren’t 100% effective at keeping the rain out. The cap will stop rain from dropping through the vent from a vertical trajectory but not from the sides. If you live in an area with heavy winds, there’s a good chance that some rain will get swept into your dryer vent. 

More Difficult to Clean and Maintain

Once you install the roof dryer vent, you’ll still have to perform occasional maintenance to keep it working correctly. Maintenance includes removing the vent cap from the end and sweeping as much of the residual dryer lint out as possible. Your roof dryer vent maintenance will prove much more complicated than if it were on the side of your house. 

roof dryer vent pipe not connected

How to Vent a Dryer Through the Roof 

While it’s not recommended, there are some situations when the only possible way to vent your dryer is through the roof. If that’s your only option, then here’s what you need to do.

1. Pick your spot for vent termination

Figuring out the exact spot where you want your dryer vent going through the roof is your first step. Figuring this out is essential, and you shouldn’t rush this step. You’ll want a spot where the vent isn’t an eyesore but also where it’s relatively easy to get to for maintenance. 

Remember, even though you’re allowed to take your dryer vent as far as 35 feet, you should try to keep it as short as possible. The shorter the distance of your flue, the better your dryer will operate. Your clothes will take longer to dry, and you’ll have more issues with lint clogs if your dryer vent is too long. 

2. Make your outside hole

Once you’ve picked the vent’s final destination, your next step is to make the hole for the roof dryer vent. Nearly all roof dryer vent pipes are 4″ round, and you’ll want your hole to be large enough for the line to fit through, but barely. Unlike other vent pipes, you don’t need several inches of clearance around the pipe to accommodate its heat. A roof dryer vent is a fire hazard if it clogs and the lint inside it catches fire. 

Trace the outline of your home, ensuring that it’s large enough to accommodate both the dryer pipe and the rain cap installed at the end. The best way to do this is to put the rain cap facedown against the roof and trace your pencil around its perimeter. Next, cut your hole with a round drill bit or a saw. 

3. Install and insulate the vent pipe itself

Next, installing and insulating the roof dryer vent pipe is time. Using a 4″ aluminum or metal roof dryer vent pipe, connect one piece to another until you have a succession of lines running from the dryer to the roof vent location. Remember, 90-degree elbows count as an extra five feet, and 45-degree angles count as an additional 2.5 feet of distance. Make sure that you don’t exceed 35 feet in length. 

Installing the roof boot for the roof dryer vent is one of the more challenging parts of the project. You’ll need the appropriate size roof flashing and some blackjack roof sealant for the waterproofing process. The roof flashing should be installed first so the dryer pipe can slip through it. 

You’ll need to slide the flashing underneath the shingles on top of the hole through your roof. Secure the flashing to the roof with 1″ roofing nails specially designed for shingles and roof flashings. Put a bead of blackjack caulk around the bottom of the roof flashing to ensure that no rain can sneak underneath the flashing and into your attic. 

Once the flashing is correctly installed, slide the dryer pipe through the hole and extend it at least a foot through the roof. You want to ensure it’s far enough through the roof so piled-up snow won’t cover it up. Anywhere the insulation doesn’t cover the dryer pipe in your attic, you’ll need to wrap insulation around it. 

4. Tape and seal your pipe joints

Once the vent is run from start to finish, it’s time to go through and tape all of the joints in the dryer pipe. Anywhere that you connected one piece to another or wherever you used an elbow, the joint needs to be taped. You can use sheet metal tape or duct tape for this process. Make sure you never use screws to attach the pieces because the dryer lint will get caught on them and cause a blockage. 

5. Install your roof dryer vent cap

Finally, it’s time to install the rain cap and dryer vent cap on the outside of your pipe, which terminates through the roof. The best way to do this is to purchase a vent cap specially designed for dryer vents going through the roof. It should keep the rain out of the vent pipe and allow dryer lint to blow freely through the exit hole without clogging. 

There you have it, how to properly run a roof dryer vent. Remember that this is the last resort for venting your dryer and should only be used when necessary. 

How to Clean a Roof Dryer Vent

It is close to impossible for one to own a clothes dryer minus a laundry machine. Yet, that’s how much our lives are dependent on technology.

The amount of laundry you do depends mainly on the number of people in your household and the children’s presence. Children need a change of wardrobe more frequently than adults do.

The more the laundry, the more the lint will determine how often you do maintenance around your home.

Reasons for Roof Dryer Vent Maintenance

  1. The recommended set-up timing for a load to be complete is between 35 to 40 minutes. If the clock keeps ticking away and your load is not thoroughly dried, you should be concerned and consider doing a maintenance job on your machine.
  1.  Vent hood flaps do not open properly. The flaps should open automatically when air from the dryer begins to flow out. If not, lint is built up, and your dryer needs maintenance.
  1. Lint and debris are expected, given that clothes wear off quickly, especially with machines. However, as time passes, lint and debris accumulate around the dryers’ lint filter; when you notice this, do a cleanup or replace the filter. Failure to clean the lint filter is the leading cause of home clothes dryer fires.
  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.
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11/09/2022 04:39 pm GMT

Roof Dryer Vent Cleaning Process

Roof dryer cleanup is a complicated, multi-step process that needs the services of a professional.

Here is a more straightforward method of cleaning up a roof dryer vent;

  1. Switch off the electricity to the laundry room and pull the dryer away from the wall.
  1. Remove the venting tube connecting the dryer and the wall from both ends.
  1.  Vacuum both the insides of the dryer and the tube to remove lint altogether.
  1.  Stick a leaf blower to the wall’s exhaust duct and wrap a garbage bag around it to trap lint flowing down the flue from making a mess.
  1.  Turn on the leaf blower and keep it running for about a minute.
  1.   Have someone on the rooftop to confirm that the lint is coming out on the other end.
  1. Turn off the leaf blower when fully satisfied that all lint and debris have been cleaned.
  1.  Connect the venting tube to the dryer and the entry on the wall.
  1.   Push the dryer back to the wall and plug it into the source of power.

Cleaning a roof dryer vent is not a DIY job and should be left to a professional cleaning service. This video demonstrates why.

When to Call a Professional

  1. Cleaning a roof-based dryer vent could be a bit complicated and require a professional to handle it. If you decide to do it yourself, you may end up damaging the roof and risk losing footing and falling off the roof.
  1. Proper roof maintenance is conducted every 2-3 years; this could also be the perfect time to ask them to check the dryer venting duct for you.
  1. If your home has a furnace, it will be good to ask the company to check and clean it for you when checking the furnace.

Roof Dryer Vent FAQs

Can You Vent a Dryer Vertically?

It’s best to vent a dryer through an exterior wall. However, sometimes this isn’t an option.

You can vent a dryer vertically as long as you don’t exceed a distance of 35 feet in length. The preferred way to vent a dryer is downward or laterally but vertically is indeed an option. There are also special considerations to keep in mind when running a dryer vent vertically. Some of these are: 

  • Always insulate your duct when running through an attic or unconditioned space. 
  • Make sure you have a vent or exhaust hood to keep the rain out of your pipe while ensuring that lint has ample room to escape. 
  • Ensure you install a dryer booster fan if your distance exceeds 35 feet.
  • The hole in your roof where the dryer vent terminates should be in a location that’s easy to maintain yet aesthetically pleasing. 

How High Can a Dryer Vent Go Up?

The maximum height a dryer vent can go up is the same as the total length of any dryer vent, 35-40 feet. The dryer vent pipe can go as high as 40 feet in the air, barring the fact that there aren’t any turns. If you insert a 90-degree elbow in your dryer duct, that counts as five vertical feet. 45-degree angles count as an additional 2.5 feet. 

The type of material that you use to vent your dryer doesn’t affect how high it can go. Aluminum, PVC, metal, and metal flex are all options for venting a dryer, but you can’t run one farther than the other. The only thing that affects how high you can take your dryer vent is how many 90-degree and 45-degree angles you have in the pipe itself. 

How Long Can a Dryer Vent Be? 

A dryer vent should not exceed 35 or 40 feet in length at the absolute maximum. Anything longer than this will require a dryer booster fan to ensure the vent doesn’t clog up.

A dryer is only designed to push air and lint up to 35 feet, so if your vent is longer, there’s a good chance it won’t make it to the outside. A clogged dryer vent is a fire hazard, and you’ll also notice that it takes forever for your clothes to dry. 

Can a Dryer Vent Turn or Change Directions? 

When necessary, your dryer vent will need to turn to vent it to the outside. There are times when you’ll have to start venting the dryer vent in an upward direction, but you’ll want to end up going out the side of your house. The main thing to remember when doing this is that you should never have traps in your dryer duct. 

A trap is when you go from up to down and back to up again, effectively forming a valley and a hill in your vent pipe. A dryer doesn’t have enough power to propel its exhaust products through a trap, and a clog in your vent will result. If you don’t form a trap, your dryer duct can make several twists and turns when necessary. 

Here are some important things to remember when changing directions with your dryer duct: 

  • It’s okay to go up or down but never do both in rapid succession with your dryer vent pipe. 
  • Every 90-degree turn adds an extra five feet to your total distance, and every 45-degree turn adds an extra 2.5 feet. It’s extremely easy to forget this if you don’t have much experience installing dryer vents. 
  • When venting a dryer pipe out through the side of your house, you need a dryer vent cap but not a rain cap. 

Can My Dryer Vent Go Through the Attic? 

You can run the line through an attic if you insulate your dryer vent pipe. You can also run your pipe through unconditioned spaces if the vent pipe is insulated. 

A common misconception is that a dryer vent has no moisture, so it isn’t insulated. This idea about dryer vents is incorrect. Dryer vents have hot air running through them, which means condensation and moisture will form when the pipe with hot air is exposed to cold air. 

If your dryer vent isn’t properly insulated, then this could result in moisture and mold issues. As long as your pipe is insulated or vented low enough so that the attic insulation covers it, you can run your dryer vent through the attic. 

Does a Dryer Vent Need to be Insulated? 

Anytime a dryer vent runs through an unconditioned space, it should be insulated. Dryer vents have warm or hot air running through them, creating moisture when exposed to unconditioned temperatures. This moisture could eventually cause mold or water damage if the pipe isn’t properly insulated. 

You don’t need overly tough or thick insulation for the dryer duct. The insulation in your attic is sufficient if you can use it to cover the dryer pipe.

Conclusion

No matter what type of dryer vent you’re installing, there are always options. Running your vent up or down or all around is allowed, but remember that the shorter the pipe length, the better off you are. If the total distance of your roof dryer vent is more than 35 feet, then you’ll need a dryer booster fan to push the air and lint the rest of the way to the outside. 

Whether you decide to run your vent yourself or have a professional install it, always remember the rules when running your vent pipe through unconditioned spaces. When in doubt, it’s always best to insulate and play it safe. Be smart, and make sure your vent is installed and maintained correctly for the best results and safety. 

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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.
DISCLAIMER: The content published on HomeInspectionInsider.com is not professional advice. You should consult with a licensed professional and check local permit requirements before starting any project.
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