Dryer vent question

[Kenneth Brown]

Finishing up all of my electrical and plumbing rough-ins in anticipation of drywall in a week or two on the new house. It suddenly occured to me that I don't have the dryer vent run yet. I don't want it to run onto the deck that goes around the house. I can run a hard line (possibly 3"pvc?) thru the wall and down till I go under the joists and then run this to the edge under the porch. This should keep condensation from under the house and eliminate an unsightly vent on the deck. Whats your thoughts?

 

[bruceb58]

Re: Dryer vent question

How long is the run and how many elbows? You need to look at the code in your area because there is a max run for 4" dryer vent. Every 90 degree bend reduces the length you are allowed to run. You can bump up to 6" dryer vent and increase the run.

3" is not acceptable at all. Your clothes will never dry because of the back pressure.

One thing you can do is add a dryer blower to your vent line. These blowers have a pressure switch that turns the fan on when the dryer turns on. I have had to add these to two of my houses because of long dryer runs. They paid for themselves in lower gas bills though

 

[Kenneth Brown]

Re: Dryer vent question

Lets see- 8" or so into the wall, 90degree bend down, 7' or so, 90 degree bend, and then about 9-10' to the cap. It almost has to be a 3" line though. I'll measure it out in the morning and see if I can squeeze a 4" in, is pvc acceptable? If I use the 4" metal line it'll give me a little more play room but then will condensation in the wall be a problem, this will be inbetween two "conditioned" spaces. This will all be inside drywall so I don't want to tear it out later.

 

[rickdb1boat]

Re: Dryer vent question

If it's in a conditioned space, you will have no problem running metal. IF any part of it is exposed to outside temps, then you will need insulation around it to prevent sweating...And from the way it sounds, you might not have the room to do that...

 

[Limited-Time]

Re: Dryer vent question

FWIW ours is vented through the roof. 1 90 and straight up and out.

 

[Kenneth Brown]

Re: Dryer vent question

Inside the wall space is limited, its a 2X6 wet wall so I have about 5 1/2 inches of wood, that leaves about 4" I can cut out, non load bearing. Outside I have all the room in the world.

 

[bruceb58]

Re: Dryer vent question

These are the fans I was talking about:

http://www.fantech.net/dryer_boosting.htm

Try to use the 4" or bigger. So you have 17' plus two 90's. That is considered a pretty long run.

This is from the Fantech site:

When to boost a dryer.
Typical residential dryers are rated at 160cfm. However, boosting is generally needed in order to maintain a minimum airflow of 100cfm as duct length increases and bends are introduced in the duct line.

Based on surveying the recommendations from dryer manufacturers, and local building codes in selected areas, dryer boosting is typically required when the duct length exceeds the following:

Maximum duct length with:

No bends 25'
1 bend 20'
2 bends 15'
3 bends 10'

 

[Mark42]

Re: Dryer vent question

The vent can also be put in the soffit if you don't want to run through the roof. My laundry is on the second story of our house. The vent goes up to the attic and over to the soffit and exits using a soffit vent. I put the vent near a second story window so I can just reach out and clean away any lint buildup.

One advantage of having the pipe in the attic is I can easily inspect it for buildup. I just pull it apart where the check flapper is (keeps cold air out) and I can see almost the entire run.

 

[Kenneth Brown]

Re: Dryer vent question

Went to Lowes and Home Depot tonight and got everything to do it in 4" metal. Really suprised me what all is actually available. I've never seen most of this stuff before and Lowes is like a second home to me.

 

[KRS]

Re: Dryer vent question

Gotta do metal. 4" all the way. Be sure you can "snake" it out when it gets clogged down the road.