Running Dryer Vent Up Interior Wall

[BikingBrian]

My dryer backs to an interior wall.  The vent currently goes through the crawl space and out of the house too low to the ground (it can flood when it rains).  I'm looking to fix that, but it means I will have to run the vent up an interior wall.



Does anyone know if there are any county codes that require rigid aluminum pipe inside the wall?  Otherwise I could use the semi-rigid expandable ducting, which would make installation easier.

[RennMan]

We have a similar problem in that the dryer is also on an interior wall, but on the second floor.  The original vent ducting is the flexible white plastic stuff.  The ductwork drops down between floors, then out through my workshop to a vent high on the first floor outside wall, perhaps 7 feet off the ground.

The problem is, after many years the plastic gets brittle, and can be easily punctured by moving or handling it.

I want to use the flexible aluminum ducting to get it snaked through between the floors, then a rigid duct to pipe the hot air to the outside.

If you use the flexible ducting, I recommend using aluminum duct, and straight runs of rigid ductwork if possible.  That's my plan...

Remember that the more bends in the ductwork, the greater the possibility of lint being trapped in the kinks and bends.  That reduces dryer efficiency, and could lead to a lint fire (if the lint builds up and doesn't get cleaned out every so often).

Just my opinion, remember it is worth what you paid for it.

Peace

[BikingBrian]

I wish I took photos of the original install.  There was the white vinyl ducting under the house, sagging in many places due to the weight of the lint.  At least as a temporary measure, I replaced the white stuff with the flexible foil stuff.

[lagomorphmom]

Couple of things to think about.

First, look at the install instructions for your dryer (probably available online if you don't still have them). There you will find the fluid-flow (remember that class in engineering school?) requirements for the exhaust install, including the allowable run lengths by duct material and number of 90deg turns.

I checked mine and found nothing about an upward ducting, but I would be VERY surprised that it would be code as lint will necessarily accumulate at the bottom of the vertical run.

In my manual, they say to never use plastic duct. Rigid metal duct is preferred over flexible and will of course give you roughly twice the allowable run length due to the smooth sides. Also, they recommend that if "flexible metal duct must be used, use the type with a stiff sheet metal wall. Do not use flexible duct with a thin foil wall. Serious blockage can result if flexible metal duct is bent too sharp. Never install any tpe of flexible duct in walls, ceilings or other concealed spaces. .....Secure joints with duct tape. Do not use screws." etc. etc.

Good luck, keep us posted!

Signed,
The Wet Blanket

[RobertW]

I don't believe you are allowed to run rigid or flex alluminum up an interior wall for a dryer.  The problem being the lint.  It is prone to a fire and you need to have access to the entire run to clean the lint out on occasion.  It is a different situation than a flue or water heater vent.

Have you thought of using black sewer piping just through the wall at it's current location, (I've heard this is acceptable for dryer venting) using a 90 and bringing it up a few inches to be above flooding water level and a cap or another 90?  90s aren't recommended because they trap lint, but the lint should collect at the first 90 at the wall which could be removed for lint removal easily on occassion. You would only have a few inches of upflow.

I'm not a contractor and this is just a suggestion.  I don't know county codes.

[BikingBrian]

I know upward venting is allowed - otherwise how could the folks back east with dryers in their basement vent them?  But they have the advantage that they can run the vent straight up behind the dryer without venting to an interior wall.  Access would be needed to the elbow at the bottom to clean any lint, but most upward installs would have that access anyway.

[cedar]

Another idea.
http://www.improvementscatalog.com/
home/improvements/75991-indoor-dryer-vent.html

I haven't tried it, but have heard you can keep the dryers warm air inside the house by using a water trap.

After looking this up for you, seems like it might be great for the Winter to have this as an alternate system.  The extra heat and humidity would be great in my house.

[Bob C]

I have something similar.. its basically a flapper valve. Flip the lever one way, and the exhaust is routed into the house. Flip the valve the other way, and the exhaust goes outside.

I did remove it, only because it broke. Yeah, you do get warmth in the house, and moisture (although it tends to have that smell drying clothes/lint give off.. not objectionable, but there).

My dryer is electric, but I don't think the exhaust of a gas dryer should be vented in doors, unless gas dryers have a separate exhaust for the flame.

[Keltnip]

We had a long run on the dryer vent at our previous house. It was not very effective for two reasons.
1) no lint trap. The line was always full.
2) because it was a gas dryer, the longer the vent the less efficient the combustion. Less drying per hour. This is also a potential CO hazard. SO be carefull if you have a gas dryer in the house.
If you run your vent up about about light switch height you will have less trouble using standard dryer materials and avoid the snow water issues you have at the present location. Higher than that you will have to consult the Uniform Plumbing Code to find the pipe/vent sizes to insure the volumetric efficiency mentioned by lagomorphmom

[lagomorphmom]

Keltnip makes some other good points.

I know upward venting is allowed - otherwise how could the folks back east with dryers in their basement vent them? 

That's not a logical conclusion because the rest of the country is primarily electric and you can vent an electric dryer indoors.

Don't forget, we're not busting your chops to rain on your parade, just to keep you all safe. Like I said before, the dryer install guide is very informative, but for upward ventilation, you really should check the code because that's for your safety also. If you go to the SB county website, it's not that bad to navigate around to find the right dept to call.

AND, if what we've brought up hasn't scared the !#$% out of you, don't forget that if you don't check code, are wrong, and a fire ensues, your insurance may not protect you....

[BikingBrian]

That's not a logical conclusion because the rest of the country is primarily electric and you can vent an electric dryer indoors.

I'm not concluding that upward venting is allowed because they do it back east.  I know for a fact it is allowed by code, my back east comment was just an example to show that upward venting was not uncommon - I grew up there and every house I had been to with a dryer in the basement vented upward and up to the outside.  (By the way, it has nothing to do with electric versus gas, it has everything to do with not adding moisture to a place where humidity is likely to already be an issue.)

Don't forget, we're not busting your chops to rain on your parade, just to keep you all safe. Like I said before, the dryer install guide is very informative, but for upward ventilation, you really should check the code because that's for your safety also. If you go to the SB county website, it's not that bad to navigate around to find the right dept to call.

I'm an engineer in my day job and so I'm used to people playing devils advocate to my designs.  But if you're going to bust my chops over something, it should at least be based on fact - don't first say that you "think" upward venting is not allowed, and then in the next post act as if it's a true statement.

Oh, and the install instructions - I don't have the ones for the dryer in WW, but I do have the instructions for the one down the hill.  There are plenty of examples of upward venting.  There are no examples of upward venting through an interior wall, but of course there won't be any because all the diagrams show the dryer on an exterior wall.

There's a PDF file on the SB County website called "Residential Building Guidelines" (or something like that) but it is silent on the particular issue of running the vent through an interior wall.

AND, if what we've brought up hasn't scared the !#$% out of you, don't forget that if you don't check code, are wrong, and a fire ensues, your insurance may not protect you....

Believe me, I'm aware of all those issues - otherwise I would have just taken the old white vinyl ducting, fished it up the wall and not even posted here to begin with!     The main reason I posted here was in case there was anything specific to SB county that I needed to be aware of.

[lagomorphmom]

I'm not concluding that upward venting is allowed because they do it back east.  I know for a fact it is allowed by code,....

I'm an engineer in my day job and so I'm used to people playing devils advocate to my designs.  But if you're going to bust my chops over something, it should at least be based on fact - don't first say that you "think" upward venting is not allowed, and then in the next post act as if it's a true statement.

You know, there's no need to get huffy. You originally asked a question and then later cited an example that related to your problem; however, you did not include the information that you had already checked local code. Everyone who replied were not familiar with local code but expressed their doubts for reasons stated and encouraged you to find out for sure which you now say you knew all along.

Best of luck with your problem.

Lagomorphmom
CSLB Mechanical Enginerring '91

[BikingBrian]

You know, there's no need to get huffy. You originally asked a question and then later cited an example that related to your problem; however, you did not include the information that you had already checked local code. Everyone who replied were not familiar with local code but expressed their doubts for reasons stated and encouraged you to find out for sure which you now say you knew all along.

If we had this conversation in person you'd see that I'm not getting huffy, after all I did have a grin in that last post!    I'm willing to chalk up any misunderstandings in tone due to this discussion being online rather than face to face.

Anyway, back to the topic - rather than say upward venting was allowed by code, I gave an example because I thought it would make the concept more clear on a non-technical forum.  In retrospect, I should have done both. 

But let me make it clear that I knew upward venting was OK per code only in the context of the vent pipe being exposed and accessible.  My particular question was about running the vent pipe upward inside a wall.  That of course has more potential issues because the pipe is then inaccessible.

By the way, all my comments above are based on national code.  I am still not yet aware of whether there are any local codes that are more stringent.  I doubt there are any, as they would likely have been mentioned in the "Guidelines for Single Family Construction", but I will still need to confirm.

Anyway, thanks to all for your genuine concerns and warnings.

Brian
WPI ChE '90