[menwork]

What is the rule or height of a chimney for a roof vented direct vent fireplace gas furnace?

[twinkiedooter]

Should be at least 36" higher than roof surface.

[hvac1000]

The code standard > The chimney must extend at least 2 feet above any portion of any structure within 10 feet (measured horizontally) AND must extend at least 3 feet above the highest point of its roof penetration.This rule has been modified or changed in many jurisdictions who now accept manufactures install instructions.

Most inspectors now rely on the manufactures install instructions since the manufactures instructions overrule most code sections. The reason for this is the fact that when the code was written back in the 1920 or there about we had limited venting and chimney assemblies to deal with. Today there are a much larger variety of chimney or venting options with the advent of high efficiency furnaces and in your case direct vent fireplaces. These items did not exist back then and that is the reason the manufacturers instructions are so important. UL and CSA do the majority of the fire testing on these devices and actually dictate how the instructions are written or modified in many cases. Since these testing agencies have proven over time how good of a job they do the manufactures install instructions are now accepted not only in the USA but around the world as the basis for a proper install.

As a general rule most direct vented fireplaces exit out a side wall of the home but I have seen some that do go out the roof.

In your case follow the directions that came with the unit. If you cannot find them contact the manufacturer or search for there directions on there web site.