[pman6]

4" sewer pipe.
Half the price of aluminum duct per foot.
Max airflow compared to corrugated flex duct.

If you were going to install rigid exhaust pipe for max airflow, this plastic sewer pipe would work well, wouldn't it?

Lowes and home depot sell them cheap.

http://www.lowes.com/ProductDisplay...gId=10051&cmRelshp=req&rel=nofollow&cId=PDIO1

http://www.homedepot.com/h_d1/N-25e...eyword=4"+pvc+pipe&storeId=10051#.UQOsrL_7KHc

 

[joecaption]

Should work fine.
If it's in an attic insulate it so it's less likly to form condinsation.

 

[jagans]

Joe's right, as usual. You can usually just run it under the attic insulation on the warm side. Hook up with a Fernco, put some SS screening on the outside

 

[joecaption]

Not liking the screen idea, a reguler siding block will work with some foil tape on it. It would just look better to me anyway.

 

[pman6]

Something interesting.

This cheap sewer pipe is made of HDPE, which I've read is a good insulator.
http://www.isco-pipe.com/products-and-services/hdpe-pipe.aspx

So you may even be able to skip buying a roll of insulation.

I'm running the exhaust to a soffit, so I'll be experimenting with this to see if there is any condensation.

If there is no condensation, this would be max performance on the cheap !