Fire DamageQ.  I'm going to put triple wall through my floor up to the roof then go back to single wall.  Is that okay?

A.  No. A lot of people think this would be a great way to save some pennies. However, it’s actually National Fire Code that once you transition to Class A pipe (aka triple wall pipe) that you cannot transition back to single wall. This code exists for several reasons.

The first reason is that single wall pipe is only meant to be a connector, meaning it must be exposed in a living space. The support boxes for Class A pipe need a special adapter piece that allows you to transition from the single wall to the Class A pipe. There is no adapter made to transition back from Class A pipe to single wall. So you’d have to simply shove the single wall in and hope for the best. This is not a positive connection.

More importantly Class A pipe is tested and designed to withstand temperatures up to 2100°F, which means it protects surrounding structures from potential chimney fires. Excel pipe carries a lifetime warranty and meets Canadian test standards (which are much stricter than U.S. standards.) Not only will single wall not contain a chimney fire, it can get hot enough to char and potentially ignite the wood around it, like this one:

Another reason it’s so important to run Class A the entire way, is for draft purposes. Newer, highly efficient stoves send just enough heat up the stack to create a draft. Meaning more heat is released into your home instead of up your chimney. (Awesome, right?) However, these lower stack temperatures mean that it’s extra important to keep the exhausting gases as hot as possible to ensure proper draft. Most Class A pipe is a stainless steel double wall packed with an inch of insulation to make sure those gases stay nice and toasty. Obviously, the gases are most prone to cooling once the pipe exits the roof and is exposed to the outside. With single wall pipe the gases will cool exponentially faster. When gases cool creosote builds up. When creosote builds up bad things happen like smoke leaks, poor performing wood stoves, and the potential for chimney fires.

So while Class A pipe is much more expensive than single wall, it is less expensive than rebuilding a home due to fire damage. And ultimately the safety of your family is priceless.