what do I use for 8" outdoor exhaust port?

My room is 15 feet, by 10 feet, with 8ft ceiling.

I have an 8" can filter and fan on the way rated at 750cm and I'm just trying to sort out a semi-stealth way to port this to the outside. I am not having much like finding any 8" exhaust ports of any kind.

Is there another way that some folks vent their exhaust air to the outside without resorting to pre-fabbed metal vents? It's kind of obvious if someone walks by and sees a massive 8" air exhaust blasting warm air out at high velocity. Most dryer, bathroom fan, and range hood ports average just 4" in size and less than 200cfm.

Looking forward to hearing some ideas and opinions on this one, it's got me scratching my head.

Thanks in advance.

ground floor? first floor? loft? can ya not just re-use the scrubbed air to heat youre house? i use two 6L rucks and one goes up my chimney the other into a room once scrubbed clean its free heat after all well not totally free but you get the drift! i hear you about the usaul 4i outlets they are crap arnt they?

Single floor. Two of the walls are exterior, so I can vent that way, and I can also access the attic directly above if I wanted to vent through the roof.

Buggins said:

and I can also access the attic directly above if I wanted to vent through the roof.

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Why not do that then, it's exactly what I do

also http://www.htgsupply.com/Product-Duct-Reducer-8-inch-to-4-inch.asp

reduce it to 6", they have nice 6" dryer vents that work and look great. i put two of them in.

build a plywood port....................or duct tape one

Will I lose much cfm reducing to 6" from 8"?

8" has an area of 50.26 sq. in. while 6" only has an area of 28.27 sq. in.
I split my 8" into two 6" without any noticeable reduction. I think just reducing it you are going to lose a lot.

If your attic is vented just exhaust it into the attic.

The attic is only passively vented, and if I'm blow 750 cfm of hot humid air up there, I know I'm asking for problems - especially with the weather cooling down and the condensation that would build up.

I managed to find an 8" roof stack that is normally used to vent a gas stove or similar appliance. Should work great, and I won't have to reduce or bottleneck it in any way.

Hanginiron, thanks for doing the math for me. That is a pretty substantial decrease in area compared to the 8" duct. That would be a massive bottleneck.

Yeah, I had already done the math. WHen I upgraded to an 8" fan and alll of my hoods were 6" it took a little figuring but splitting into 2 6" ducts seems to work out fine. I haven't actually measured the cfm but I am able to run 4k without ac...except in the summer, of course.

HanginIron said:

Yeah, I had already done the math. WHen I upgraded to an 8" fan and alll of my hoods were 6" it took a little figuring but splitting into 2 6" ducts seems to work out fine. I haven't actually measured the cfm but I am able to run 4k without ac...except in the summer, of course.

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How about a pic of the junction? Buy it pre-fab or rig it?