I’ve been running into a lot of furnace vents that are using the bendable corrigated vent pipe like you would use on a dryer vent. I see it on new construction and old. I thought the vent pipe had to be rated. Is this still true or is this new kind of vent pipe ok to use now?
Thanks for your input.
Sid 
It could be right, can’t realy tell from a pic. but there is a flexible vent pipe for that application that is alot thicker than that used for a dryer. i’ve seen Harry Homeowner use the wrong stuff though.
Flexible vent piping is manufactured in a variety of materials and used for many different types of applications.
Suitability for a particular application is generally dependant upon the manufacturer’s recommendations.
If proper labeling or documentation is not available for this particular installation (at time of inspection), a recommendation for further review to determine manufacturer compliance is justifiable.
Try the above URL.
OK, try the below URL.
oh make up my mind already
There’s a lot of new flexible vent material out there that is rated for high-temperature flues. That’s about all I see in new construction around here because it’s so easy (read, less money for labor costs) to install. Based on that bottom fitting in the picture, that looks like the appropriate rated stuff.
I believe the venting material must be Stainless steel. Not aluminum.
I have not asked the manufacturer’s for the composition of their approved vents, but they do look like aluminum. However, they are not flimsy like the dryer flue connectors. Perhaps I’ll check in at Home Depot later today and see if I can get one out of the box or read the exterior bos labeling to see what it says.
The ones I see are labeled as a B-vent connector and there is a warning that they are not allowed to pass through walls or ceilings. The label also states a minimum 1-inch clearance to combustibles. This one looks like it has a label as well. Need to read it to see if its approved.