had a dealer at my house yesterday to look at proposed venting thru my basement window.this is what he proposed.this is all 4" duravent pro 3" to 4" t off stove 6 ft vert 90 elbo 18" hor thru window outside t 5ft vert 90 elbo jet cap install was $380 piping was $850.(same pipe on dynamitebuys is $530). i dont think i need all that pipe on the outside.i can meet the clearance of 18" off the ground.the only concern is clearance to the gas meter.my enviro meridian install manual says 36" from center of meter to vent termination(page 10).i went to building inspector yester but he was out doing inspections.his secretary said he tells everyone to install acording to manual.i can meet the clearance to the meter also.with a whole inch to spare even.so my piping configuration will now look like this. 3" to 4" t off stove 6ft vert 90 deg 18" hor thru window jet cap all for a grand total of $330 from dynamitebuys and this is also for black pipe. a question i had for you all is,i will be taking the window sash out and my plan is to cover both sides of the window with 1/2" cement board and insulate between.am i correct in assuming i do not need a thimble since i am passing thru a non combustible wall.