If the climate in your area is very cold insulate the chase to the top to keep the chimney warmer increase the draft and reduce creosote buildup.
Fireplace attic chase.
A chimney installer indicated that i would need a firestop in this chase between the first second floor and another one 8 feet up from that.
Measure the height of the furthest point of the installation.
The rsf manual in the section about chases though they mean outer wall chases says.
As currently designed the distance inside the chase to the chimney or firebox will be more like 24 on average with the closest spot about 6.
You can also taper the chase above the fireplace.
Climb into your attic and locate where your chimney system will enter this space.
Inspecting the firebox clearances is more challenging.
The base of the chase must accommodate the framing dimensions of your fireplace.
If this height exceeds 15 you are okay to install a attic insulation shield.
The chimney chase top chimney chase cover is usually metal constructed of formed aluminum or stainless steel.
Seldom do we think about the fireplace metal vent pipe running up through the attic and roof.
We also recommend to insulate the ceiling of the chase just as if it were in the attic space.
Smaller dimensions for a rough frame of a chimney chase are about two square feet.
Most of the units inspected by chimney professionals are improperly installed and a trip to the attic to check clearances is definitely time well spent.
However a home inspector may tell you that there is no fire stop or that it is installed wrong.
Fire stops are self describing.
Any wood that is too close to the chimney will undergo a process called pyrolysis and even catch fire at temperatures as low as 200 degrees.
The interior of the chase has plenty of clearance to the fp and chimney.
They are installed to stop a fire in the chase area where the vent pipe runs through to get to the roof.
Doing this leaves room to encircle the chimney pipe.
After you know where the penetration point will be for both attic and roof add 2 to all sides.