Can a Dryer Vent Pipe Go Up Vertically?

Dryer vent cap on the roof of a house

Clothes dryers are pretty much a standard commodity in most of today’s homes. If you don’t have direct access to a dryer in your home, you likely have access to one in a laundromat. If you live in an apartment, most complexes have a laundromat or laundry room on site. With all the dryers in the world, there are many different ways to vent them based on your situation. 

When necessary, a dryer vent pipe can go up and vent vertically. Dryers are designed with multiple options for venting because venting dryers isn’t one-size-fits-all. If the situation calls for it, then you can vent your dryer up, down, or sideways depending on where the termination needs to go. 

Venting a dryer upward has different rules and stipulations than venting sideways or down. There are many things to remember when it comes to dryer venting to maximize safety and effectiveness. To find out more about how to properly vent your dryer, keep reading. 

How High Can a Dryer Vent Go Up?

The maximum height that a dryer vent can go up is the same as the total length of any dryer vent, 35-40 feet. The pipe that’s venting your dryer can go as high as 40 feet in the air, barring the fact that there aren’t any twists or 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 up 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. 

Diagram of a proper vertical dryer vent

Can My Dryer Vent Go Through the Attic? 

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

A common misconception is that a dryer vent doesn’t have any moisture, so it isn’t insulated. This idea about dryer vents is incorrect. Dryer vents have hot air running through them, which means that when the pipe with hot air gets exposed to cold air, condensation and moisture will form. 

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 attics’ insulation covers it, you can run your dryer vent through the attic. 

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. Venting through the roof should only be used as a last resort, however, 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 on them, 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 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. If your dryer vent is on the roof, maintenance will prove much more complicated than if it were on the side of your house. 

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 vent is, 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 dryer vent. Nearly all 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 the heat that it gives off. A dryer vent is only a fire hazard if it clogs and the lint inside of it catches fire. 

Trace the outline of your home, making sure that it’s large enough to accommodate both the dryer pipe and the rain cap that’s getting 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 either a round drill bit or with a saw. 

3. Install and insulate the vent pipe itself. 

Next, it’s time actually to install and insulate the dryer vent pipe. Using a 4″ aluminum or metal 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 dryer vent is one of the more challenging parts of the project. You’ll need the appropriate size roof flashing as well as some blackjack roof sealant for the waterproofing process. The roof flashing should get installed first so that the dryer pipe can slip through it. 

You’ll need to slide the flashing underneath the shingles on the top side 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 in the flashing and extend it at least a foot through the roof. You want to make sure it’s far enough through the roof so that piled-up snow won’t cover it up. Anywhere that the dryer pipe isn’t covered by the insulation 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 that you never use screws to attach the pieces because the dryer lint will get caught on them and cause a blockage. 

5. Install your dryer vent cap and rain cap. 

Finally, it’s time to install the rain cap and dryer vent cap on the outside of your pipe, where it terminates through the roof. The best way to do this is to purchase a vent cap that’s specially designed for dryer vents going through the roof. It should fulfill the job of keeping 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 dryer vent through the roof. Remember that this is the last resort for venting your dryer and should only be used when absolutely necessary. 

Vertical dryer vent not connected to the roof cap in the attic

Can You Vent a Dryer Vertically?

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 that you have a vent or exhaust hood that will keep the rain out of your pipe while making sure that lint has ample room to escape. 
  • Make sure that you install a dryer booster fan if your total 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. 

Can a Dryer Vent Have Twists and Turns in It? 

When necessary, your dryer vent can have a twist or turn in it in order 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 be the result. As long as 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 ok to go up or down but never to 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. 

Does a Dryer Vent Need to be Insulated? 

Anytime that a dryer vent is running through an unconditioned space, it should be insulated. Dryer vents have warm or hot air running through them that will create moisture when exposed to unconditioned temperatures. This moisture could eventually cause mold damage 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 that’s in your attic is sufficient if you can use it to cover the dryer pipe. If that isn’t an option, then wrapping the pipe with any type of insulation is sufficient. 

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 that the vent doesn’t clog up.

A dryer is only designed to push air and lint up to 35 feet, which means that if your vent is longer than that, there’s a good chance it won’t make it all the way 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 Tumble Dryer Vent Go Up? 

Installing the vent for a tumble dryer is slightly different than that of a typical dryer, but you can still run the vent upward if necessary.

Tumble dryer vents need to be a little bit shorter than other dryers, but the vent can still run vertically when necessary. You can even have twists and turns in your tumble dryer vent as long as the vent doesn’t exceed 25 feet in length. 

Final Thoughts 

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 always remember that the shorter the pipe length is, the better off you are. If the total distance of your 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 it comes to 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 properly for best results and for your own 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.
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