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Choosing correct duct?

I need help picking the suitable product and figured I'd ask the people with firsthand experience.

So I've got about a 15' run thru 3 6" sealed hoods, the fan is an 8" hyper fan pulling thru a 8" phresh carbon filter. I'm hoping to exhaust the room via the filter and dump the heat into the living space of the home.

My question is what type of flexible duct should I use? Home depot and lowes carry the really flimsy
Aluminized mylar $12, or the insulated 2 layer plastic duct $30. What should I be using?
 
The shiny mylar stuff is full of pinholes and can leakk light and odor.
The insulated stuff wont but obviously its mucho more spendy.

i prefer the insulated stuff but am using mylar at the moment. Both work.
 
Last edited:

DrDee

Member
Hi Fitz,
I'm setting up my ventilation like you...dumping the warm filtered air to living space. A little nervous if I ever have an infestation and need to treat plants.

Anyway, heard guys claim the insulated duct acts to suppress sound from fan motor too...so seems that's the best bet.
JD
 

f-e

Well-known member
Mentor
Veteran
Insulated ducting is often fiberglass filled. Fiberglass is horrible stuff. I have worked with asbestos, and the guys that taught us drew no line dividing asbestos from fiberglass. Telling us the only reason fiberglass was allowed, is because there is too much in use to regulate it.


Your fan should be coupled to your filter, without flex between them. Partly this reduces fan noise, but it's a loss of power if the fan has to pressurise any air volume, and if that air is in a flexible container, It's even harder to transmit the pressure from the fan to the filter medium. Flex leads to an inefficient system, that means turning up the fan further. If you have the spare capacity.

I presume your blowing backward through the filter. If the fan is bolted straight to it (or better still, using a foot of hardpipe for meaningful noise reduction) Then your duct run to the tent can be a bit porous. Any holes won't let air out. Air will come in.

This all leads towards a visit to the local air handling experts. They sell good ducting without holes. Foil/fibreglass reinforced pvc/metal/plastic whatever. They also sell metal fans, which are suitable for the higher temps involved with shifting hot air. More so then plastic. It's also wholesale prices. Need an excuse?

Excuse for insulated.
Your electric bill is massive. You have built a workshop at the back, and heating it with electric is costing the earth. You want to take some air from beside a blow air heating vent in the house, and pipe it through the garage rafters to your workshop.

Excuse for normal
You want to vent the paint? fumes from your internal garage. So your putting a fan at the back to suck in air and pipe it back out the front.

Both excuses are just a confidence boost. They won't even care. They sell fans and duct 'all day long' it's their business.
I 'always' buy from them, and they never ask what I am doing, expecting the whole plan. Their only concern is selling you bits that fit together.

Where you join the 8" AND 6" is debatable. The same air volume going down a 6" as an 8, needs to be traveling perhaps twice as fast in the 6" sections. Which can be a lot more noisy and turbulent. Sapping power from the fan.

I have gone way past ducting 101, and forgot the opening post lol
 

Drop That Sound

Well-known member
Ideally you would want rigid metal ducting for most of the run, and flexible insulated or maybe semi rigid (aluminum) just where the hoods connect, so you can still raise and lower them. I find it all super cheap at local construction recycling\salvage stores. Same with the fittings, I save like +80% compared to HD and Lowes, and I selectively pick out brand new stuff mostly.

I agree with the cheap flimsy mylar ducting being crap, with pin holes. But it does work, I just plan to replace it often when used. It works better than insulated ducting if you sleeve a piece of 8" over the 6", especially if your worried about glass strands contaminating the grow. That shouldn't be a problem though if you wrap the exposed ends well.

The cool thing about rigid metal ducting is you can always insulate around it later, but it flows so much better that you probably won't need to. And you can paint it if you want, which is nice if you find some that used and you want it to look brand new.
 

CannaRed

Cannabinerd
So do you guys ever insulate the fan itself? I wasn't sure if that was a good idea or not. Thought it could cause fan to over heat, but it's exhausting the air over the motor so shouldn't be a problem right?
 

siftedunity

cant re Member
Veteran
theres no need to insulate a fan, just insulated ducting either side of it. its definitely not gonna make it any quieter and most likely isn't safe.
 

f-e

Well-known member
Mentor
Veteran
I havn't purposefully insulated a fan, but have boxed them, which is very normal. As said, their heat leaves in the air stream.

What I invariably have to do is wrap gaffer tape round them at some point during their life. The assembly method used at factory, leaves tiny gaps in the casing. Sometimes gaps where the wires come through into the electrical terminal box. Who's lid is also not air tight. They're not gas tight. They may leak just 0.1% and still be a smell issue.


I'm loving fast clamps. OK, so a few cable ties will do, especially under vacuum with a low budget. Jubilee clips or banding is pro. Fast clamps though.. You can butt a fan and filter together, wrap with gaffer to seal, then fast clamp. And it's sorted. Remember fans, mufflers, filters, lots of things are the exact same size so won't slot together. They slot to duct. So if you want a fan with muffler each side, fast clamps are the way. Then you could support the mufflers with whatever your suspending them with, and the fan would be happy just held between them with the clamps. The clamps also offer tabs to use themselves as hangers. It's costly, but if that falls apart you must of had a decent quake.

I'm actually a dab hand at this. I make stuff I really should market. But it's not the thread.
 

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