Thread: Extended length vent

I know this is not an HVAC topic but I cannot find the area in the forum that covers Dryer vents, so here goes:

I am seeing more and more of new construction large houses with this dryer vent length disclaimer, when the vent length is extended due to the large attic space the dryer vent go through. The IRC used to be 25 feet, but now it appears the length has been increased in a new code release? When I read the new revision, there are enough exceptions to cause it to be confusing. I cannot seem to find any consensus on dryer vent length. Then there are some dryers that are rated for extended length vents. Those of you that are seeing these extended length vents, how are you handling them on your reports?

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Originally Posted by Gene South

I know this is not an HVAC topic but I cannot find the area in the forum that covers Dryer vents, so here goes:

I am seeing more and more of new construction large houses with this dryer vent length disclaimer, when the vent length is extended due to the large attic space the dryer vent go through. The IRC used to be 25 feet, but now it appears the length has been increased in a new code release? When I read the new revision, there are enough exceptions to cause it to be confusing. I cannot seem to find any consensus on dryer vent length. Then there are some dryers that are rated for extended length vents. Those of you that are seeing these extended length vents, how are you handling them on your reports?

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At least you are fortunate enough to have found one with the warning and the developed length filled in. Many times you will find no sticker and no length. Dryers, many dryers, now have the ability to use longer than the old standard 25 feet, minus 2.5 feet for 45 degree fittings and minus 5 feet for 90's.

As long as the dryer installed is rated for the length they are fine. If the sticker is missing or the length not identified and a person puts a standard dryer in that is not rated for the length it is a fire hazard.

Oh, and this is the correct area. HVAC stands for Heating Ventilation and Air Conditioning.

Dryer vent length should not exceed dryer manufacturer recommendations. Vent length may differ from appliance to appliance. Exceeding recommendations may create a fire hazard, or at the minimum reduce clothes dryer efficiency - for example; it takes longer to dry clothes.

If you find the sticker, I would leave it at that, assuming of course that is is not an obvious lie!
I might mention it to a client to keep that in mind while shopping for that new dryer.

Dryer exhaust duct length (it's not a "vent") is, and has been, required to be posted on a permanent plaque at the dryer connection end when the dryer exhaust duct is not visible to determine the effective length.

I know this is in the Mechanical Code, and I'm pretty sure it is in the Residential Code but will need to verify that.

From the IRC:
- M1502.4.5 Length identification.
- - Where the exhaust duct is concealed within the building construction, the equivalent length of the exhaust duct shall be identified on a permanent label or tag. The label or tag shall be located within 6 feet (1829 mm) of the exhaust duct connection.

Originally Posted by Jerry Peck

From the IRC:
- M1502.4.5 Length identification.
- - Where the exhaust duct is concealed within the building construction, the equivalent length of the exhaust duct shall be identified on a permanent label or tag. The label or tag shall be located within 6 feet (1829 mm) of the exhaust duct connection.

Thanks Jerry. You're da Man, as always.......

A few days ago, I saw a booster fan for the dryer vent. I had never seen one before. I wonder if there are issues with lint collecting on the fan blades.

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