Use what the stove shop recommends. Use what the installer says to use. The insurance company would appreciate it.

Use 8 only Triple Wall pipe if you chimney goes through the walls of your home, any 2nd story and/or attic. The outer diameter will be 8in the inner diameter (where the heated smoke will travel will be 6inches)
It may be more expensive but your insurance company & loved ones will thank you in the long run. I used triple wall Simpson-Duravent from my basement ceiling up 30 ft to extend 4 ft beyond the opening of my metal roof home. I burn a Hearthsone Heritage woodstove.

woodinvirginia, is using the 8" a safety issue, or does it make your stove work better? Ours will go through a wall and up thru high rafters. Thank you.
Thanks, also, Chrisopher.

you have to use the pipe the fireplace tells you to use if they say you can use either 6 or 8 use six for money savings. Im in the business if you get me the make and model i can help make that decission

I'm with christopherh. Get an installer with experience. Also also get the penetration finished before the roofers come in. Make sure they(roofers) make a channel to divert all roof water away from the penetration. Just advice from our experience.

In our case we installed a lopi liberty wood stove. I had asked the installer about triple wall pipe. He said we didn't need it. We have a small attic penetration but most of the double wall is exposed. I was concerned about heat but after 2 years of cranking the stove up, my concerns about the double wall were unfounded.

Peace

Its a safety issue. Most of these us don't know what type of insulation you will be using in your attic, Glass, cellulose, foam. etc. We don't know if down the road some one other than you will make a mistake & put cardboard or luggage, wiring or anything flammable near to this chimney over the next 30 years . What you are doing is "prevention of anyone" not necessary you of making a faux pas that ends up costing you the homeowner. Some one once said 'penny wise but pound foolish!'

Sure appreciate everyone's knowledge and advice. Thank you, Jeanie

We, too, are about buy chimney pipe. We have 16 inch center scissor trusses and a vaulted ceiling. It looks like we can center our pipe (triple wall?) to miss the trusses. Have any of you made a box made out of Durock or some noncombustible material to go through our small attic? Or do we need to buy one made of metal? Thanks! Liz