Trap Door Style HVAC Wall Caps - Need Recommendations

[larry4406]

Currently I have conventional wall caps for dryer and bath fans as shown below. Ignore the capped electrical conduit as it is just protecting a pneumatic line from the barn from UV exposure (not hooked up yet).


Our master bath addition will occupy this space. It will be built elevated like a deck with a horizontal trimmed bottom lid. Rendering from similar vantage point with framing diagram below. Perimeter joists in green, dropped beams in yellow. There will be an under build to flush out the bottom of the beams and create a single horizontal plane for the bottom lid to be installed. In-field framing will be 2x10 joists sitting on existing house sill plate and sistered to existing joists, bear on intermediate and end beams, and hangered to end

Thus, I have to relocate these wall caps.

I have been thinking of possibly turning them down and exiting the horizontal trim bottom lid using a spring loaded trap door type vent. The bottom lid will be a solid surface (MDO with batten strips). Some random examples found on line shown below (ignore the vented soffit shown in the example). Alternately, I can extend the ductwork 15' and continue using the same type wall cap that I have now. I was told the orange box store had this type of cap but I did not see them when I was there today.

Concerns with wall caps that mount on a horizontal surface?
Hot humid dryer exhaust creating a mold farm on the bottom lid? The footprint of the addition is 15' deep and 13' wide.

 

[75gmck25]

Dryer exhaust is warm and humid, and always has some lint in the airstream. I would recommend finding an exhaust path with the fewest bends, and use all rigid metal vent except at the connection to the dryer. Also figure out where you will be able to open it up and run a brush/snake through it to break loose anything that is clinging to the inside of the pipe. Dryers work much more efficiently when there is less resistance to air flow out.

Bath fans are less fussy for the venting, but using a similar scheme is good idea. They will often need to exhaust more humidity, but the dust level is just whatever is floating around in the air.

 

[larry4406]

Dryer exhaust is warm and humid, and always has some lint in the airstream. I would recommend finding an exhaust path with the fewest bends, and use all rigid metal vent except at the connection to the dryer. Also figure out where you will be able to open it up and run a brush/snake through it to break loose anything that is clinging to the inside of the pipe. Dryers work much more efficiently when there is less resistance to air flow out.

Bath fans are less fussy for the venting, but using a similar scheme is good idea. They will often need to exhaust more humidity, but the dust level is just whatever is floating around in the air.

Agreed. Thanks for the feed back! This thread kind of went nowhere...

Here is before.

Here is after first deck today. Dryer is far left. On the right side, the left cap of the pair was a spare for a basement future dryer and is deleted.

So I either extend these all 15' and exit the new band board, or I turn 90 down and exit out of the lid below. Below exit would need the trap door style cap that the original post is all about.

Here is new band board 15' further out. Each elbow is worth 5' they say, so going straight is just a 10' more penalty.

Current dryer is around 20' assuming the one included elbow is worth 5'. Interestingly, reading the dryer specs just now, say its good for 125' of equivalent length with rigid duct which is what I have! So, I guess I am going to use a traditional wall cap!

 

[PCustoms]

Any chance of moving the laundry to in the master bath?

Not sure I'd want to dump that under me new addition.

Surprised that's not PT framing...

 

[thammel]

My comment is about plastic vs stainless steel wall caps. I had a couple plastic ones that fell apart after a few years of sun exposure. You can buy pretty nice ones in stainless steel from Amazon. If you want the best quality ones, in a variety of metals and/or finishes, check out luxurymetals.com. Not cheap but really nice!

 

[geneg]

My comment is about plastic vs stainless steel wall caps. I had a couple plastic ones that fell apart after a few years of sun exposure. You can buy pretty nice ones in stainless steel from Amazon. If you want the best quality ones, in a variety of metals and/or finishes, check out luxurymetals.com. Not cheap but really nice!

A friend of ours had bath exhaust fans venting thru the attic wall with flex duct & plastic wall caps. Red squirrels chewed the plastic caps & the flex duct. They created an entire neighborhood in her attic. She had critter control trap them. I then piped the fans with aluminum ductwork inside of flex insulated fiberglass ducts (prevents condensation on the aluminum in the cold attic) to stainless steel wall caps. Also check to see if the cap has hardware cloth inside the flaps to ensure there is no access if the flap or louvers stick open.

 

[larry4406]

Any chance of moving the laundry to in the master bath?

Not sure I'd want to dump that under me new addition.

Surprised that's not PT framing...

The laundry room is in a closet off the main hall so accessible to all, so its not moving. The specs for the dryer great exceed the normal 25' limitation so I will be extending it straight out thru the deck. Same for the basement bath fan.

Yeah I was concerned about dumping it under the new addition as well. Hence the statement in the opening post.

Regarding not using PT framing, the posts will be PT. There will be an under build at the level of the beams and a flat bottom lid installed after spray foam insulation. The entire addition will have matching Hardy cement board siding.

 

[larry4406]

..... Also check to see if the cap has hardware cloth inside the flaps to ensure there is no access if the flap or louvers stick open.

The bath fan cap has hardware cloth while the dryer vent does not. Screens on dryer vents is not recommended due to the lint build up.

 

[geneg]

The bath fan cap has hardware cloth while the dryer vent does not. Screens on dryer vents is not recommended due to the lint build up.

Yes, I should have said that. My ss dryer vent has 5 horizontal shutters. I've never found any stuck open.