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I own a home built in 2003. The laundry room is in the middle of the house, but also adjacent to the garage. I live in Florida.

The dryer venting system is close to the floor, turns 90 degrees, goes straight up, and into the attic. In the attic it does a 45 degree bend and travels directly to the roof. The vent is somewhere between 18 and 20 feet long.

I have had a long history of dryers lasting only a short time. I typically get about 2-3 years out of a dryer. The last dryer that died, I took apart and the dryer had all kinds of lint on the internal parts. My prejudice is that since the vent does not work very well, the lint gets blown back into the dryer, and kills it.

BTW, I regularly clean the dryer vent with one of those brush, drill and extension flexible pole things. I clean it about every 6 months and just did it the other day.

So my current dryer is acting up. When vented to the duct, clothes will dry after about four or five 70 minute cycles. When I vent directly into the garage, the clothes dry in about 50 mins. (This is done by running the flexible hose from the dryer through a door open to the garage.)

What can be done here? Should I redo the duct through the roof? Should I pursue venting directly into the garage? Who is qualified to do this kind of work? I don't think I can pull this one off myself.

Again, we live in Florida so it has not been bad leaving the door to the garage open as it has been pretty cool, but in the summer this would stress our AC unit and run up our electric bill.

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    Sounds like your efforts at cleaning may not be helping and may be making things worse. It may just be shoving the lint down the pipe further, clogging it more. Can you positively inspect each section of the pipe? Or no? I have a feeling if you dismantle the 45 degree pipe through the attic, you will find a frightful mess.
    – Harper - Reinstate Monica
    Commented Mar 5, 2018 at 22:40
  • I have had a home in Central Florida 15 years .. with a vent through the roof, from my floor It went 90 degrees and straight up through the attic and out the roof (@25 feet I think - my ceiling was vaulted at 16 feet and attic had about 6 feet) and I had no issues (I still have the same dryer 22 years old now - I clean its lint trap every dry cycle @30 - 45 minutes to dry a large load Never needed to do redo's). I wonder if your vent has a blockage in it or is capped on top preventing rodents / birds from crawling in ? What is the diameter 4 inch all the way ? Mine was.
    – Ken
    Commented Mar 7, 2018 at 7:26
  • Just another quick answer the spin cycle of your washing machine should have your clothes damp but not wet and this will affect dry times too.
    – Ken
    Commented Mar 7, 2018 at 7:39

6 Answers 6

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Add both a secondary lint trap and a dryer duct booster fan. Fantech and Tjernlund are a couple brands to help you start your search.

Also, replacing any easily accessible flexible duct with rigid ducts can help prevent lint from building up.

Finally, check that the exhaust louver/vent cap outside isn't filled with lint too. Sometimes contractors use dual use intake/exhaust vents and forget to take the intake screen/mesh/filter out that is used to keep bugs from flying inside when used as an intake.

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  • Any idea who can add those things? Just a general handyman?
    – Pete B.
    Commented Mar 5, 2018 at 14:09
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    HVAC contractors are familiar with venting ducts for kitchens, bathrooms, dryers, etc. For a smaller job you may get a better deal from a good general handyman.
    – Stanwood
    Commented Mar 5, 2018 at 14:30
  • The booster fans I have installed for dryer ducts were cord connected and had a sensor when it got warm the booster kicked on until 10 minutes after the temp was below set point, an easy DIY. Cut flex duct install the booster with the arrow away from the dryer and 2 zip ties to hold the duct on the booster. I used large hose clamps instead of the zip ties so I could inspect it. The great thing was lint quit building up and my clothes dried in 1 cycle. The secondary lint trap may be a good idea but my install it was not needed.+
    – Ed Beal
    Commented Mar 6, 2018 at 0:35
  • A “mechanical contractor” is a superset of an HVAC one and can also deal with ducting.
    – rrauenza
    Commented Mar 6, 2018 at 3:57
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    All are good suggestions, but based on your (the OP) calculations, you shouldn't need a booster fan, and if adding one, you often add a number of extra issues with it as well (that can all be overcome of course, like Ed mentions) just note you will have to clean the fan too! Be sure to consult the manual that comes with your dryer as it tells you the max run for its ability to move the water column
    – noybman
    Commented Mar 6, 2018 at 4:57
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Your duct experiment and past experience indicates that the existing venting is limiting the performance of the dryer. You can't vent into the garage (see below) and being in Florida I assume you are on a slab so there won't be some alternate route into a basement or crawl space.

Your best solution may be a condensing (ductless) dryer.

This snippet of residential code outlines the problem and the solution [emphasis added]:

M1502.1 General. Dryer exhaust systems shall be independent of all other systems, and shall convey the moisture to the outdoors.

Exception: This section shall not apply to listed and labeled condensing (ductless) clothes dryers.

M1502.2 Duct termination. Exhaust ducts shall terminate on the outside of the building. Exhaust duct terminations shall bein accordance with the dryer manufacturer’s installationinstructions. Exhaust ducts shall terminate not less than 3 feet(914 mm) in any direction from openings into buildings. Exhaust duct terminations shall be equipped with a backdraft damper. Screens shall not be installed at the duct termination

[BUILDING] Building shall mean any one- and two-family dwelling or portion thereof, including townhouses, that is used, or designed or intended to be used for human habitation, for living, sleeping, cooking or eating purposes, or any combination thereof, and shall include accessory structures thereto.

Previously asked on SE

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So years later I hired someone to install a booster fan. Luckily he was a good guy and told me I didn't need that. He took the ducting apart in the attic. Sure enough it was clogged with lint. The brush and flexible pole thing didn't work sufficiently it still allowed link to build up near the top.

He cleared that out, and the dryer worked just fine afterwards. It would be advisable for a person with a similar setup to take the ducting apart every couple of years to give a good cleaning.

I won't be doing this as I since moved to a home with more sensible dryer ducting. The new home has a host of other problems but drying ducting isn't one of them.

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I wrote up a Q & A adventure I took with this same problem. I listed the math used and the performance considerations. Also, I ended up buying one of those pressure sensors as well to at least alert me when lint needs attention. 6 months is a good guideline but you mileage may vary.

Things like how large is your family? How often is the dryer used? Also, have you invested in a new washer? I'm not asserting that your washer is the culprit, but to be honest, as long as the dryer doesn't have a bad pressure issue or a back flow problem (like wind across your roof flowing back into the dryer) then it shouldn't be taking more than 1 drying cycle.

What size is the washer vs. dryer? Is the dryer rotting out or the motor burning out? You should also clean out the dryer itself from time to time as well.

Either way - it is probably a good idea to re-think your duct run. Use rigid smooth ducts, no screws, do not use booster fans if you can at all avoid it. Make sure your duct goes out a gable or some non-weather facing side of the house if at all possible. Since you are in FL the roof is probably ok but given your experiences, it might be worth rerouting it. Minimize bends and consult the dryer manufacturers run-length calculations as they typically exceed the general code guidelines and that is ok!

Here's my info: Dryer Venting Woes - what to do?

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  • Great idea using a pressure sensor to alert you of a lint problem!
    – Dotes
    Commented Mar 6, 2018 at 14:17
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If the vent run is too long or has too much resistance due to sharp bends, and there are little other options on where your vent could be run then I'd consider switching to a more expensive condenser or heat pump dryer.

These closed circuit dryers do not require venting as they extract and condense excess moisture into a tank or drain. As with alternative technologies, they come with their advantages but also disadvantages such as increased drying time.

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my dryer recently stopped working and gave me a D80 code which meant it was 80% blocked. I bought one of those long dryer brush/drill extensions and had minimal results. I watched a video of a guy cleaning his vents with a leaf blower. Worked like a charm.

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