Dryer Vent Installation: Can Dryer Vent Through A Roof?

According to The International Residential Code requirements on the length of the venting duct, it states that a venting duct should not exceed the maximum length of 35 feet starting from where the dryer is to the termination end, which could either 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 route 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 risk lint build-up becoming a fire hazard.

The code goes ahead to reiterate that the venting duct should be as straight as possible right from the start to the end. Turns and bends interrupt the flow of air and could become potential catchment areas for lint.

Demystifying 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 is becoming commonplace in modern-day construction.

In the past, homeowners and venting system manufacturers were more focused 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. Proximity of the neighboring 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 – dryer vents low to the ground can be damaged by children or pets.

1. Proximity Of The Neighboring Homes

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

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

2. 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.

According to building codes, 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 if you had the dryer vent professional cleanings annually or as needed.

3. Aesthetics

Modern homes are keen on both style and beauty

No one wants vents that are protruding out of 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 most probably go for roof system dryer vents.

4. Length Of The Duct

As much as the International Housing Code recommends a 35 foot maximum in 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 dryer vent fire.

5. 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, 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 increased fire risk.

6. Damage

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

Approval from Authorities

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

1. Building Code

The International Residential Code, together with The International Mechanical Code, unanimously states 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.

2. 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.

3. 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.

 How to install a dryer vent on the roof

  1. From the location of your dryer inside the house, locate the point of exit on your rooftop where you would want the vent to terminate. 

Use a tape measure to make out the distance between the two points. If it falls below 35 feet, you are good to go, but anything above requires that you relocate your dryer and the venting system to a different location than meets the standard length.

  1. From inside the roof and on the exit location in the attic, trace the outline of the venting duct on the roof, then drill a hole through it before cutting around the outline using a reciprocating saw to make a hole through which the outline roof venting cape will come in.
  1. Then from the rooftop, cut and trim the shingles lying over the hole to make a delicate edging. 

Install the vent cap by inserting the pipe through the hole, then attach the cap firmly on the siding or the roof deck. The pipe should extend down the roof so that you may access it from the inside. 

To keep the vent cap in place, you may require the use of regular 11/4″ nails to fix the venting cap to the siding or galvanized roofing nails to attach it to the roof decking.

  1. Spread roofing tar around the diameter of the hole to seal it completely and prevent water from dripping in.
  1. Again from inside the attic, make a hole on the ceiling that will accommodate and allow the pipe to run straight from the roof down to the dryer.
  1. Insert a 4” metal duct elbow upward inside the vent at the back of the dryer, firmly securing it using a duct clamp.
  1. Now, connect the dryer to the roof vent using a 4” metal duct pipe.
  1. Reinforce every joint along the duct using metal foil tape.

Disadvantages of a Roof Dryer Vent

Water damage

During a storm, there is a chance that a roof venting system may contribute to more roof damage, especially if the area sounding the duct cap is not well secured, or the roofing tar did not glue everything in place.

 A damaged roof will see water trickling down inside your home, damping and damaging the ceiling.

Moisture drainage

Hot air rises and makes it easy to be transported up (along with lint) through the vent and out the venting system. But when the cycle completes, the remaining water vapor might condense along the way and then trickle down the venting duct bringing lint down with it.

Moisture drainage could cause unexpected lint build-up calling for early or an emergency cleanup.

Cleaning 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 children’s presence. Children need a change of wardrobe more frequently than adults do.

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

Reasons For Dryer Maintenance

  1. The recommended and 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, then you should be concerned, and you should consider doing a maintenance job on your machine.
  1.  Vent hood flaps do not open properly. The flaps should flap open automatically when air from the dryer begins to flow out. If not, it means there is lint 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 goes by, 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.

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 exhaust duct on the wall and make sure to wrap a garbage bag around it to trap lint that will be flowing down the tube from making a mess.
  1.  Turn on the leaf blower and keep it running for about a minute.
  1.   Have someone on the rooftop who will confirm that the lint is coming out on the other end.
  1. Turn off the leaf blower when you are fully satisfied that all lint and debris have been cleaned.
  1.  Connect back 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 Use a Professional

  1. Cleaning a roof-based dryer vent could be a little bit complicated and may need a professional to handle it. If you decide to do it yourself, you may end up damaging the roof and put yourself at risk of 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.

Conclusion

As discussed earlier, roofs sometimes provide shorter vent pipe runs for dryers. However, the length of the run also reduces efficiency. The longer the run, the more friction loss is created, so the building code restricts total run length. 

Lint build-up is the root cause of all dryer vent problems. Ensure to clean the lint filter every time before running the dryer, and this will be one step every other time to win against lint build-up and potential safety hazards.

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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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