# Dryer Venting through an unfinished attic



## Magnettica (Dec 19, 2006)

I am wiring for a new stackable washer/ dryer combo tomorrow and was asked to do the venting at the last minute. I plan on installing 4" galvanized up and into the attic space and then using flexible insulated venting to the gable side and venting out. 

I have some of this left over from a bathroom exhaust fan job and was wondering if it'll be good for dryer venting too. My main concern is the plastic enclosed around the aluminum body would it be likely to cause a fire. 

Like this....


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## genecarp (Mar 16, 2008)

More appropriate is full rigid pipe, but that flex is used ALL THE TIME, GMOD, BTW by the time the exaust gets up to the attic fire in the pipe is not a concern.


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## Magnettica (Dec 19, 2006)

What if I did do the full rigid duct work? Would I just need to wrap it with insulation or is it not even necessary once I get into the attic? 

Thanks...


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## genecarp (Mar 16, 2008)

Magnettica said:


> What if I did do the full rigid duct work? Would I just need to wrap it with insulation or is it not even necessary once I get into the attic?
> 
> Thanks...


If you go hard pipe all the way, no need to insulate, but is so much easier to transisition to flex, the typical dryer vent flex has no insulation, what you have there mostly gets used for AC, but since you have it, transision to that in the attic, and get er done, GMOD


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## Magnettica (Dec 19, 2006)

Nice Gene. Much appreciated for the advice. And that's exactly what I'm doing.... Git er done!


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## naptown CR (Feb 20, 2009)

even down here they make us use hard pipe all the way. no screws just metal tape and if run through an unconditioned space (attic) we are required to insulate it and slope toward the outlet (Condensation inside the pipe will accelerate lint build up.) I have used the flex duct but only sleeved over the hard pipe as insulation. 5" works nicely. I believe this is a code item in the newer codes also.


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## Rory Read (Feb 5, 2010)

*metal flex, right?*

I am a plain old remodeler, not an HVAC guy, so pardon my ignorance, but we are talking about wrapping metal flex with the pictured insulation, not just the insulation, right?

The owner needs to be able to clean it out with a brush for fire safety and dryer efficiency sake, and I am pretty sure no manufacturer would be ok with just the above.

I know the ideal installation is rigid duct, insulated, with maybe a short near- straight metal flex or adjustable metal section to ease the install.

r


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## genecarp (Mar 16, 2008)

Rory Read said:


> I am a plain old remodeler, not an HVAC guy, so pardon my ignorance, but we are talking about wrapping metal flex with the pictured insulation, not just the insulation, right?
> 
> The owner needs to be able to clean it out with a brush for fire safety and dryer efficiency sake, and I am pretty sure no manufacturer would be ok with just the above.
> 
> ...


 
No Rory just the insulation, only for the last few feet up in the attic, hard pipe will come out of the dryer through the first floor, into the attic. No HO is brushing out 14ft into the attic, Most HO never ever bother to clean out anything, they call when there clothes are not drying, then i clean it out, GMOD


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## Rory Read (Feb 5, 2010)

*no doubt*

GeneCarp,

I have no doubt that's the way it is and that's the way it's done.

At the same time, I know a fire fighter who mutters something about dryer vents every time he passes a laundry room. So I google dryer vent fire hazard, and the third hit is this from Consumer Reports:

February 2008
Dryer fire caution

More than 13,000 fires a year start in laundry rooms in the United States, resulting in 10 deaths and $97 million in property damage. Nearly 4,000 of these fires arise from lint buildup that occurs when people fail to clean their dryer vents. The following safety information from _Consumer Reports_ can help you prevent a disaster....

I have no skin in this thread and certainly respect the way it is commonly done. For all I know CR is full of it. But I do know how I am going keep installing these things.

Cheers,

R


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## genecarp (Mar 16, 2008)

Rory, if something works for you by all means keep on doing it, i was curious, so i googled dryer fires also, here is what came up

*LINT RELATED FIRES IN DRYERS: by Charles C. Roberts, Jr. *








Many dryer related fires are attributed to lint accumulation in the dryer as a result of several causes. Improper maintenance of the lint trap is at the top of the list. Lint from clothing can enter the dryer cavity through improperly installed or damaged lint traps and contact hot surfaces such as electric heating coils or the flames of a gas operated burner. Damaged drum seals, door seals and other dryer components allow lint into the dryer cavity. Finally, restrictive dryer vents cause reduced air flow and high temperatures in


If the customer does not maintain the lint trap, we could be using clay flue pipe and it would still burn according to this. I dont know whats the truth really is, i only know what i have been doing for 30 years, and what i see, to each his own, GMOD​


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## Rory Read (Feb 5, 2010)

*yup*

Gene,

Your quote & post make sense to me.

R


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## neolitic (Apr 20, 2006)

Magnettica, if they have soffit vents,
and they should, you may just be
cycling it back through the attic.
Keep it as far away from vents
and windows as you can.


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## Magnettica (Dec 19, 2006)

Thanks for the heads up, Neo. 

I actually searched the site here before posting and found this to be a bit interesting. 

http://vcisafety.org/dryer_vent_fires.cfm


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## beenthere (Mar 5, 2009)

Many areas here require it to be a metal vent, no vinyl.

And yes, it must be insulated. Or you'll have more water in the vent then you know what to do with.


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## Tinstaafl (Jan 6, 2008)

genecarp said:


> No Rory just the insulation, only for the last few feet up in the attic, hard pipe will come out of the dryer through the first floor, into the attic. No HO is brushing out 14ft into the attic, Most HO never ever bother to clean out anything, they call when there clothes are not drying, then i clean it out, GMOD


You're probably right about most HO's, but sooner or later someone's going to have to do it. And that flex duct would totally suck when the time comes. There's a fair chance it would have to be replaced.

Rigid all the way. :thumbsup:


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## seeyou (Dec 12, 2008)

genecarp said:


> If you go hard pipe all the way, no need to insulate,


That was the source of a "mystery" leak. Fairly long run of rigid pipe through the attic. When it was near or sub zero, a wet spot was showing up on the ceiling. Nearby plumbing vent and roof vents that could have been the culprit. Finally got in the attic at the right temp when the dryer happened to be running. Spotted the drip from condensation near the end of the pipe, coming from a joint. Joint had been taped, but condensation build up had broken the seal down (my guess). Had it insulated, problem solved. 

To the OP, I'd run rigid pipe through the insulated flex you have unless your temps stay pretty warm. Belt and suspenders.


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