Breather Valve Question

[CapePizza]

I'm planning on installing a breather valve on top of the dome. After researching what others have suggested/used I bought a valve shown in the photo from Napa Auto. Wasn't expensive. Maybe $12, if I remember correctly. After I got it and investigated how it works....I see it's not really a "valve" at all. It's kind of both an inlet and outlet. It can act as a release for any steam build up but can also allow moisture to enter. Am I interpreting this correctly and is this what's intended? In a moist environment such as where I am I'd rather not give moisture a chance to enter the space in the dome where the insulation resides. Wouldn't it be better to have kind of a one way check valve sort of set up.... letting built up steam out, but closing off a way for moisture to enter? Letting "stuff" out, but closing off from anything entering?

[cobblerdave]

G’day john
I think if you change some terms here it might put things into context. Change “steam”
for “moist air”. The vent just allows an escape point for moisture as the oven heats. You’ll not get steam venting in a plume from that point.
As for letting in moisture . No not really it’s the firebricks natural tendency to take up water from the air is where the moisture gets into the structure. Regular use minimises this.
I live in the subtropics my own oven is rarely 100 per cent dry due to humidity. I except this and just use it for what it is.
That looks like a good cap, insect and child proof and not dependant on remembering to screw a cap back on
regards Dave

[CapePizza]

thanks for the comments, Dave. I hadn't thought about the bricks themselves just sucking up moisture from the environment. I had thought the purpose of the breather cap was to kind of help in preventing any steam build up between the bricks, insulation and outer render.. and cracking the dome..... giving any steam a way out, sort of speak. So maybe the breather cap is just that.... it allows the space between the outer render and the bricks to just.... breathe.

further edit: In thinking about this a bit more, regardless of where the moisture comes from, if it gets in between bricks and outer render, the idea is get rid of it, expel it. not allow any over build up of either moisture or steam. The breather cap provides for the moisture and/or steam (if there is a steam build up) to expel. But why not just have a one way valve? I guess I'm not understanding why the oven would need an inlet.... seems like it would just want an outlet (like a one way valve).

[Gulf]

Dave is correct in his description. It can be called a vent, or a breather. It is just not a "valve". You are also correct. It's purpose is to not allow a pressure build up inside and to keep rain water out. It will let a lot of moisture out, but the amount of moisture returning via humidity would be minimal imo. I agree that what you have pictured will work just fine. However, I would not use the pvc fitting that you have pictured. Instead, I would use a threaded pvc bushing. Here is a link that may help explain how that will better anchor the reciever into stucco or mortar. The only thing different that I would do from what is picturef in my link is to use 2 electrical conduit lock nuts instead of 1. One on each side of the mesh.

[CapePizza]

Thanks Joe and Dave(again) for the help. Joe, I had previously seen those pictures from the link you provided. I was intending on adding a locking setup of some sort and trapping the 1/2" hardware cloth as you show it using a threaded bushing (just wasn't shown in the picture I posted). I was going to do the bottle in the Pcrete (leaving a hole of sorts) and then mortaring in the breaker cap set up. I'm assuming the bottom of the PVC opening just rests on top of the insulation blanket. Thank you both again for the help and clarification.

[Gulf]

I only anchored the mesh and fitting into the stucco layer. I filled the beer can sized hole in my vecrete up with excess blanket. V and P crete both will have some trapped moisture for months after they are set in place. I felt like that would give the moisture from it a little extra place to exit. Imo the bottom of the pvc opening needs to be as high as possible based on the theory that steam rises.