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Thread: Dryer Vents

  1. #1
    mathew stouffer's Avatar
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    Default Dryer Vents

    This is a question I should know, but one I have never really asked myself. Does the IRC require a dry to be vented to the exterior in a single family room. I know the length requirements on the vent but is it required to vent if a dryer is installed.

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    Default Re: Dryer Vents

    Quote Originally Posted by mathew stouffer View Post
    This is a question I should know, but one I have never really asked myself. Does the IRC require a dry to be vented to the exterior in a single family room. I know the length requirements on the vent but is it required to vent if a dryer is installed.
    Absolutely!

    (Unless the dryer is a condensing dryer.)

    - 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.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  3. #3
    mathew stouffer's Avatar
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    Default Re: Dryer Vents

    So if I slap a hallway closet laundry room in my 3 million dollar home, five years after the home is built it requires an exterior dryer vent. Would a lint box ever suffice.


  4. #4
    Robert Schenck's Avatar
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    Default Re: Dryer Vents

    Matthew – I see Jerry hit the nail on the head. The IRC M1502.1 makes it easy to understand. Clothes dryers produce lots and lots of moisture, along with a substantial amount of lint that doesn’t get filtered out by the dryer.

    This moisture and lint needs to be discharged to the exterior of the house. The external lint trap you’re speaking of does not allow the moisture to discharge to the exterior of house and from what I hear – doesn’t catch 100% of the lint.

    So over time – if you choose the external lint trap – the moisture is going to take its toll on the immediate area of where the dryer is located. Not only will moisture be an issue – but your wife having to clean up the loose lint not caught by the trap will become a pain in the arse. Besides – I don’t know why you felt the need to mention “my 3 million dollar home”, but it doesn’t matter if it’s a 3 thousand, 300 thousand or a 3 million dollar home, whether its 5 days, 5 months or 5 years old - moisture and lint are not particular. It should vent to the house exterior.

    (I know the length requirements on the vent but is it required to vent if a dryer is installed.) Odd question, but yes. If there’s a dryer vent there – then a clothes dryer should be able to vent – to the “exterior”.


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    Default Re: Dryer Vents

    Quote Originally Posted by mathew stouffer View Post
    So if I slap a hallway closet laundry room in my 3 million dollar home, five years after the home is built it requires an exterior dryer vent. Would a lint box ever suffice.
    Unless you're installing a listed residential condensing clothes dryer, identified in the plans and actually installed. If installing non-condensing dryer you will also require sufficient make-up air (being exhausted mechanically via dryer vent) and if fuel-fired dryer - additional combustion air - for venting dryer the make-up air supply and if applicable combustion air supply must be available whether the "closet" doors are open or closed.

    You'll also have to "slap" a dedicated laundry circuit (grounded and GFCI protected) supplied receptacle for the laundry "area" even if you don't expect to be ironing, etc. there (closet isn't a "room") and you may or may not require a means for ventillation and light (depends on the configuration, etc.) since the laundry area as opposed to a clothes or storage closet is expected to be occupied (not habitated) and the moisture generated during clothes washing & drying activities may require exhaust venting to control negative effects on the adjoining living space & structure.


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    Default Re: Dryer Vents

    Quote Originally Posted by mathew stouffer View Post
    So if I slap a hallway closet laundry room in my 3 million dollar home, five years after the home is built it requires an exterior dryer vent.
    You betcha, unless the dryer was a condensing type dryer.

    Would a lint box ever suffice.
    Nope, a lint box is not needed with a condensing dryer ... oh ... you mean with a regular dryer ... er ... what part of "M1502.1 General. Dryer exhaust systems shall be independent of all other systems, and shall convey the moisture to the outdoors." needs to be explained further?

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  7. #7
    Don Burbach's Avatar
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    Default Re: Dryer Vents

    Matthew, I've pondered several scenarios:

    1. Business is slow and you're tired of going to the laundromat.

    2. A Realtor told you that those lint boxes really work, and you believed'em.

    3. You added a zero, but you really have a $300,000 house.

    4. A seller hacked your business account and is trying to get even with you for calling out the lack of a dryer vent.

    5. You and a bunch of other inspectors have a pool about who would answer faster; HG or east coast Jerry.

    My money is on #5, and Jerry!


  8. #8
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    Default Re: Dryer Vents

    Good one Don That was worth a few chuckles. The real reason is someone called me out on this and I said it was required but never looked it up. I was 90 percent sure. After confirmation from these posts I get to lay the beat down on them

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    Default Re: Dryer Vents

    Then add to the fact that almost no manufacture would allow that type of ducting for their warranty then you really got em ; )

    Do we need to mention the fire danger also.

    Don Hester
    NCW Home Inspections, LLC
    Wa. St. Licensed H I #647, WSDA #80050, http://www.ncwhomeinspections.com

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    Default Re: Dryer Vents

    I inspected a 1200sq.ft. house yesterday where the previous owners attempted a garage conversion. They installed a free standing wall 1/4 of the way in from the garage door forming what looked like a storage room. This wall had a window and door opening but no window or door installed. They used the remaining space for a bedroom. This bedroom area was also used for the air handler,which was in its own closet space, and an electric water heater that was out in the open sitting on the floor. Next to the WH was the space for the washer and dryer with the dryer vent connection directly above in the ceiling. In the attic I was able to see the flex duct looping back into the front area by the garage door. The lint was recirculating back into the bedroom. This room configuration looked like something from an M.C. Escher print where you can't determine what's up or down or whether you're coming or going.


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    Default Re: Dryer Vents

    Quote Originally Posted by Robert Schenck View Post
    . . . . . Not only will moisture be an issue – but your wife having to clean up the loose lint not caught by the trap will become a pain in the arse. . . . .
    I am not going there. Just not going there.




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    Default Re: Dryer Vents

    I hope that the attached photos give some idea of why venting a dryer to the outside is imoprtant. These photos came from a condo community where I was doing a reserve study. And, a LOT of the dryer vents were like this, which makes me believe that other issues might exist. (I am also think that the black stuff in the one photo might be remnants of the bird kind.

    But, I am not so certain that the dryer boxes are a solution. Some of these devices work by impingement of the ot air onto a water surface, that is blowing the air directly at the water surface. Impingement would capture larger fibers, but not the smaller ones. The smaller ones are an issue because they don't settle out of the air as fast as the larger ones and can travel throughout the building until they finally settle out or get attracted to another surface or particle. So, accumulations of lint dust in the building can still occur. As I found out years ago after being awaken in the early morning hours by a hotel fire alarm going off, that lint is highly flammable. Then, there is that issue with these devices going dry and not working at all, and the issue with all of the moisture being put in the air, which could be worse because this device also puts moisture in the air.

    A filter could also be attached to the outlet. But, to be able to capture all of the lint, the filter would have to have a relatively high efficiency. A higher efficiency means greater pressure resistance. The greater the resistance per area or filter; the more the dryer air flow is reduced. And dryer fans are not made to counter a lot of resistance. (Thus, the limitations on duct length). So, the size of the filter area would have to be increased to reduce the overall resistance. That could mean a very large filter box. Then, there is that issue with the moisture being put in the air.

    Speaking of moisture, have you ever done an inspection where you see moisture condensed on and/or dripping off of ductwork during the cooling season or possible signs of such moisture issues? You might also find signs of mold growth in areas where the ducts have leaks. One of the first things to suspect is a leaking dryer duct or unvented dryer.

    Matt also mentioned knowing the length requirements of the ductwork. Keep in mind that those are general guidelines. Not all dryers have the same duct size requirements. The ultimate authority is the manufacuter, which specifies which duct size/lengths can be used. Also keep in mind that type of duct and the number and type of bends also affects how long the duct can be. The numbers are for effective length, which is related to total resitance (pressure drop), not actual length.

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  13. #13
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    Default Re: Dryer Vents

    Quote Originally Posted by Matthew Klein View Post
    I hope that the attached photos give some idea of why venting a dryer to the outside is imoprtant. These photos came from a condo community where I was doing a reserve study. And, a LOT of the dryer vents were like this, which makes me believe that other issues might exist. (I am also think that the black stuff in the one photo might be remnants of the bird kind.

    But, I am not so certain that the dryer boxes are a solution. Some of these devices work by impingement of the ot air onto a water surface, that is blowing the air directly at the water surface. Impingement would capture larger fibers, but not the smaller ones. The smaller ones are an issue because they don't settle out of the air as fast as the larger ones and can travel throughout the building until they finally settle out or get attracted to another surface or particle. So, accumulations of lint dust in the building can still occur. As I found out years ago after being awaken in the early morning hours by a hotel fire alarm going off, that lint is highly flammable. Then, there is that issue with these devices going dry and not working at all, and the issue with all of the moisture being put in the air, which could be worse because this device also puts moisture in the air.

    A filter could also be attached to the outlet. But, to be able to capture all of the lint, the filter would have to have a relatively high efficiency. A higher efficiency means greater pressure resistance. The greater the resistance per area or filter; the more the dryer air flow is reduced. And dryer fans are not made to counter a lot of resistance. (Thus, the limitations on duct length). So, the size of the filter area would have to be increased to reduce the overall resistance. That could mean a very large filter box. Then, there is that issue with the moisture being put in the air.

    Speaking of moisture, have you ever done an inspection where you see moisture condensed on and/or dripping off of ductwork during the cooling season or possible signs of such moisture issues? You might also find signs of mold growth in areas where the ducts have leaks. One of the first things to suspect is a leaking dryer duct or unvented dryer.

    Matt also mentioned knowing the length requirements of the ductwork. Keep in mind that those are general guidelines. Not all dryers have the same duct size requirements. The ultimate authority is the manufacuter, which specifies which duct size/lengths can be used. Also keep in mind that type of duct and the number and type of bends also affects how long the duct can be. The numbers are for effective length, which is related to total resitance (pressure drop), not actual length.

    I install and clean dryer vent systems all the time, part of the business. The vent covers that Matt has shown are a good example of why dryer vents should be maintained every year. Those vent covers in Matt's photos get replaced out all the time by me because they are made cheap. I have attached two files. 1) pdf for the IMC; 2) pdf for a double door vent cover which a better design then the old ones.

    Please also include the IRC and the IMC coupled with HOA guidelines for dryer vents.

    Attached Files Attached Files

  14. #14
    Robert Schenck's Avatar
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    Default Re: Dryer Vents

    . . . . . Not only will moisture be an issue – but your wife having to clean up the loose lint not caught by the trap will become a pain in the arse. . . . .
    Rod - Little did I know how silly the comment I posted sounded .... until you quoted me - lol. Derr me


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