Flexible insulated duct

[Todd.Brock]

How do you guys feel about insulated duct work? I have 2 bathrooms that have I have replaced the exhaust fans with super quiet Panasonic high CFM fans.

The directions weren’t super specific about what to use. I used rigid 4” for most of one run, but getting into the soffits with rigid was going to require a bunch of flex elbows.

I decided to call Panasonic and they said I could use flex duct for the last 3 ft of the run. I have never worked with stuff but it seems pretty flimsy. The plastic is thin at best, but it did make it easier to get into the soffit.


Should I just **** it up and hard pipe this stuff or am I ok with the flex duct?
Soffit connection and pic of the 2nd soffit vent waiting connection.

 

[Todd.Brock]

This was supposed to be in the Heating and Cooling. Mods- can you relocate?

Thank you

 

[K'ledgeBldr]

Most fart fans use "uninsulated" flex- depending on the length of the run (code).

So to answer your question- No; don't see a problem with what you have.

 

[Fixed]

It'll work. If you have a short run I wouldn't worry. If it's in an attic and you're in a cold climate then the insulated is great for reducing your mould risk.

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[peter2772000]

It'll work. If you have a short run I wouldn't worry. If it's in an attic and you're in a cold climate then the insulated is great for reducing your mould risk.

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This!

Flexible duct ruins efficiency when you run excessive lengths. We like to terminate rigid runs with 3-6' of flexible, acts as a bit of a muffler for possible air noise.

 

[Fixed]

This!

Flexible duct ruins efficiency when you run excessive lengths. We like to terminate rigid runs with 3-6' of flexible, acts as a bit of a muffler for possible air noise.

In commercial installs in my area, a length of flex from elbow to diffuser is almost always specced out for that reason.

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[peter2772000]

Here too, and we're also in the commercial sector

 

[Todd.Brock]

Well heck fire. Guess it isn’t as rigged as I thought. In that short run, I would have needed 3 flex elbows if I used rigid.

It is quiet! I’ll say that. It’s just that plastic duct is flimsy. I used worm clamps and then taped with foil tape.

It’s right against the roof deck too. I hammered a couple nails so they were bent over a bit so it didn’t stick the insulation.


Thanks again!

 

[Trey T]

Need to vent it up thru the roof to prevent moisture building up the roof deck near the soffit.

 

[NUTTSGT]

This was supposed to be in the Heating and Cooling. Mods- can you relocate?

Thank you

I moved it earlier this morning to General Discussion without thinking or reading the entire thread. I opened it up and saw what it was and moved it out of GenTool. I should have pair more attention but it's in the correct section now.

Sorry about the delay.


I wouldn't sweat a small section myself.

 

[Todd.Brock]

Thanks NuttsGT!

Trey. The builder had it running just into the soffit , blocked off by some batt insulation. That to me did not seem any different than just letting it vent directly into the attic. Wanting to do this correctly, I called the building inspector and asked what the new requirement is. Ironically, I was not thinking about using insulated ducting when I talked to them. I did not think to ask about insulated ducting and if it was up to code. I will have to hope for the best. They told me it had to penetrate the Exterior of the building.

I bought two soffit vents and it now route directly to the outside.


Did I mention I don’t like heights?

 

[zmaxmotorsports]

Around here fart fan lines have to be insulated,whether they're rigid or flex lines.

 

[AP514]

hum my Fart Fan just vents into the attic....Is that a bad thing ?
My Shower exhaust vents outside...

 

[Todd.Brock]

I wouldn’t get a fart fan in the attic would hurt anything. No different moving conditioned air into the attic vs outside...

My fans are a shower/fart combo so they had to go outside

 

[Ohmthis]

A few (3-5) feet won't hurt anything. Just make sure that the bends aren't squishing the flex and causing flow problems. Here everything in an unconditioned space has to be insulated, some for efficiency, but mostly to prevent condensation.

 

[Fixed]

I wouldn’t get a fart fan in the attic would hurt anything. No different moving conditioned air into the attic vs outside...

My fans are a shower/fart combo so they had to go outside

No don't vent a bathroom fan into your attic, shower or not. Warm air moving into your attic is the opposite of what you want, the RH is still very high, shower or not. Also against code... Well, everywhere.

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[larry4406]

Around here fart fan lines have to be insulated,whether they're rigid or flex lines.

Same here new construction northern VA and MD.

 

[ripperd]

hum my Fart Fan just vents into the attic....Is that a bad thing ?
My Shower exhaust vents outside...

In texas you might be able to get away with it. But certainly not in any colder states...

I wouldn’t get a fart fan in the attic would hurt anything. No different moving conditioned air into the attic vs outside...

My fans are a shower/fart combo so they had to go outside

When the weather gets colder, that air coming from inside the house is much warmer and more humid than outside air. Your attic should generally be the same temperature as outdoors. If you dump humid shower air at 80% humidity and 70 degrees into a 30 degree attic, guess what happens? As the air cools the humidity will condense out onto the cold surfaces (insulation, roof decking) and form condensation or frost. Lets this continue for a bit and pretty soon you will have mold and rot.

Venting like this into a vented (perforated) soffit is also going to be a problem.

Today's building codes specifically require this type of vent to be vented to the outdoors, and there is a minimum distance from the outlet to any vent inlet (including soffit vents).