# Such a thing as a double bathroom vent wall cap?



## bob_cntrctr (Jan 30, 2008)

Gentlemen,

Remodeling two side-by-side bathrooms on the second floor of an old brick home. By happy coincidence, there is already a ~8" x 4" hole through the brick wall up near the ceiling in one of the bathrooms. Looks like it was long ago for vent pipes, but someone plugged it up with the most incredible mixture of newspaper, crumbling mortar and tin cans (no joke).

Anyway, to avoid going through the roof, I want to use this hole for both bathroom vents. Two 4" ducts will fit perfectly, but only if they're right against each other. Maybe 1/2" spacing is possible - but I've never seen wall caps designed to be placd that close together. Even if you butt the exterior plates right up against each other, there's going be ~1" between the pipes for most models I've ever seen.

I don't really want to downsize to 3" and ruin performance. And I'd rather not have to enlarge the hole.

I could use just a single vent by either:

a)two separate fans, Y them together into one vent and make sure there are back-draft dampers on each fan - not bad, but you're really depending on that damper.

b) single fan with single vent, drawing on both bathrooms, - never been a 'fan' (get it?) of this - seems to me a lot of wasted room air venting both all the time.

BUT, if there is such a thing as a dual-pipe vent cap out there that might do the trick, it'd mean being able to keep them separate. Anyone seen such an animal?


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## neolitic (Apr 20, 2006)

You can search other threads here,
but bottom line is joining them is
a no-go.
You might find a range hood cap
sized right for the side-by-side.
Seems like 4X10 is a standard size,
not sure.


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## j_builder (May 10, 2008)

To be code compliant you might want to go with your plan A Bob.

Here's some more information http://www.rd.com/familyhandyman/content/53294/


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## HVAC_Ryan (Jun 18, 2008)

*Is a Commercial Hybrid an option?*

Bob,
I suppose it starts with how much are you willing to spend, and what you are looking for?
If you've done any commercial projects you may remember that they typically place washrooms etc. back to back to minimize wall penetration points. 
You could go all out and talk to a Sheet Metal contractor you work with and ask him to draw something up and have it made for you, I can't see this being too expensive. Ask them to provide a Louver custom painted to match the exterior brick colour. 
 As a visual reference take a look at: eccoduct. com / ventilation .html

I'm still a new user so you'll forgive me for asking you to remove the spacing and insert the above as a web address?


Ryan


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## bob_cntrctr (Jan 30, 2008)

j_builder said:


> To be code compliant you might want to go with your plan A Bob.
> 
> Here's some more information http://www.rd.com/familyhandyman/content/53294/


 
I think you meant to type "plan B". Ya, typical - a Fantech inline downstream of a Y. Just, like I said, it seems terribly wasteful. But if it's that or break more bricks...

Figured the two-fan push into a Y would not pass.


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## mdshunk (Mar 13, 2005)

Actually for bath fan venting (not mixing with products of combustion), you can compliantly wye two 4-inchers into a minimum of a 6" round duct. Six-inch wall caps are a common stock item. 

It is somewhat common in apartment buildings for a whole floor of bath fans to dump into a common large exhaust duct.


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## bob_cntrctr (Jan 30, 2008)

Aha - now we're getting somewhere. Well if Y-ing two fans passes, then borrowing from HVAC_Ryan and combining with mdshunk produces something I DO like AND would pass: a custom fabbed, 4" x 8" square wall cap with dual 4" round ports each with a backdraft damper.

No prob for cost - Between wrench turning and renos I've fabricated my share of tin. A 4x8 boot, couple 'o collars, little while with the snips and the spot welder....

Thank you gentlemen. vbmenu_register("postmenu_455524", true);


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## j_builder (May 10, 2008)

mdshunk said:


> Actually for bath fan venting (not mixing with products of combustion), you can compliantly wye two 4-inchers into a minimum of a 6" round duct. Six-inch wall caps are a common stock item.
> 
> It is somewhat common in apartment buildings for a whole floor of bath fans to dump into a common large exhaust duct.


Excellent idea mdshunk:thumbsup: I've never seen or even heard of such an idea, course thats why I'm here to learn from the pro's on this site.


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