Dumb question on attics and vents/airflow

[kyphysics]

I'm wondering if attics supposedly have air vents to let air flow in and out, how is it that these "holes" in the attic also don't let water come through during rain?

 

[berkeman]

Like these type of attic vents? Looks pretty rainproof to me...

https://www.gaf.com/-/media/hero/pr...hash=3AB0548E9D44315297DE8CDB6AC201C32CCBF9B5

 

[Klystron]

Vents in attic walls are protected by louvers; horizontal slats set at an angle to inhibit rain but allow air. Louvers also keep out larger pests such as rodents and birds.

Vertical vents commonly use pipes through the roof. The top of the pipe is protected by a raised cone or cap larger in diameter than the pipe. Rain splatters off the cone but air comes through the gap.

Any of these openings can be protected by a metal mesh, a screen that allows air flow but inhibits insects. Some attics have small screened windows perhaps with an overhang.

[Edit: 20200302: added cap to standing pipe.]

 

[anorlunda]

Pictures are worth a thousand words.

There are many more variants.

Edit: LOL @berkeman found the same picture as I did, but faster.

 

[Klystron]

Pictures are worth a thousand words.
[...]
There are many more variants.

True, but I love using words such as "louvers".

 

[berkeman]

Vertical vents commonly use pipes through the roof.

So you are asking for unprotected vent pipes protruding out of the roof? I'd guess that their j-traps keep water from backing up, but I don't know that for sure. I'll Google a bit more...

https://i.pinimg.com/originals/0d/72/41/0d7241ce5b63f17b835e6eeb1b971988.jpg

 

[berkeman]

but I like your spinning cap shown in your first post.

You just gave me serious vertigo, and my stomach contents are now cleared. Thank you very much.

I think you meant to reference that *other* poster's reply about the spinning attic vent. I need to go lay down for a few minutes...

 

[berkeman]

So you are asking for unprotected vent pipes protruding out of the roof? I'd guess that their j-traps keep water from backing up, but I don't know that for sure. I'll Google a bit more...

https://i.pinimg.com/originals/0d/72/41/0d7241ce5b63f17b835e6eeb1b971988.jpg

View attachment 258026

Ah, I understand how the unprotected vent pipes drain now. They drain out of the overall house drains...

https://en.wikipedia.org/wiki/Drain-waste-vent_system

 

[kyphysics]

Pics are very helpful.

I see more of the "vertical" vents in my neighborhood. Always wondered how they worked. Figured if you had a hole, "stuff" could come in (bugs or water). Thanks for the pics and explanations!

 

[Lnewqban]

Pics are very helpful.

I see more of the "vertical" vents in my neighborhood. Always wondered how they worked. Figured if you had a hole, "stuff" could come in (bugs or water). Thanks for the pics and explanations!

Most building codes require an insect screen behind the louvers and any other path into the attic.
With enough wind speed, rain-driven rain will penetrate the attic space.

Some industrial and properly designed louvers reduce that type of penetration very well.
Please, see:
https://www.archlouvers.com/How_Louvers_Work.htm

 

[Rolacycle]

I'm wondering if attics supposedly have air vents to let air flow in and out, how is it that these "holes" in the attic also don't let water come through during rain?

Depending on type of house your talking about (gable/hip) there are 2 basic types of intake flow vents (gable vent / Soffit vent) respectively. House that have gables usual don’t have as many exhaust flow vents due to flow ability and how wind can drive thru attic. There is a specific formula based upon surface area of roof : area of house footprint that calculates needed intake surface area and proper exhaust flow depending on vent type. But as long as your shingles (laminated) don’t look like burnt toast intake/ exhaust ratio isn’t damaging shingles

 

[Averagesupernova]

The vertical pipes sticking out the roof have nothing to do with ventilating the attic. They are sewer vents.

 

[Averagesupernova]

If anything drains into the sewer vent is considered part of the drain waisted vent system and will be protected with a trap to prevent sewer gas from escaping. Whatever device that drains into the sewer vent happens to reside in an attic well then that is coincidence. The sewer vent is meant to vent the sewer system, not the fixture or appliance that happens to be hooked to it or space the said appliance resides in.
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Edit: I should be a little more careful with my wording. A vent pipe that is part of the main DWV system that runs from an individual sink for instance is said to vent the sink. But what it actually does is allow air to follow the drain water away from the sink. If this is not provided there is danger of the trap under the sink being drawn empty or close to empty which will low sewer gas into the room.
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So again, the vertical pipe pictured in post #6 is just a sewer vent and nothing else.

 

[Rolacycle]

If you post picture of exactly what you what identified I’ll answer with the exact answer

The vertical pipes sticking out the roof have nothing to do with ventilating the attic. They are sewer vents.

or vent for a gas appliance,
vent-a-hood for stove top
Few others that off the top of my head escape me

 

[Averagesupernova]

If you post picture of exactly what you what identified I’ll answer with the exact answer

I referred to the pic in post #6. 'Nuf said I think.

 

[Rolacycle]

I referred to the pic in post #6. 'Nuf said I think.

Is that what he was referring to because that’s not clear from anything I read?

Or just what someone else posted picture of?

maybe Texas jack or a one way HE water heater? Or chimney even

 

[Averagesupernova]

Someone has deleted their post. I thought they were referring to the pipe in post #6. So, this is what my replies were aimed at. I have to assume who delete and dash poster was figured out they were wrong. Chicken way out if I've ever seen it.

 

[Rolacycle]

Someone has deleted their post. I thought they were referring to the pipe in post #6. So, this is what my replies were aimed at. I have to assume who delete and dash poster was figured out they were wrong. Chicken way out if I've ever seen it.

Ahhh well those are definitely pvc (1-1/2” ; 2” ; 3” ;4” etc.. ) vents that supply sewer drain air relief for anything that drains to city connected water supply in #6 comment right