Insulation in Chase

[thanley]

I've got the chase open and am finalizing prep for the z42.

I'm hanging 1/2 inch cement board on both the sides and back of the chase going 6 feet up and was planning on just having insulation secured above that to the first firestop between the first and second floor.

Talking to a builder buddy of mine and he said it didn't matter if I used kraft backed insulation between thes studs and the cement board or if it was unfaced. This came about because I have had zero luck finding unfaced r13 insulation here in Indianapolis.

Given that the insulation will be exposed another three feet above the cement board line I'm looking for input on this (though I think I know the answer already).

there was NO insulation in the chase originally when I ripped out the old unit so I'm just making sure I'm doing this right once and for all.

 

[DAKSY]

I've got the chase open and am finalizing prep for the z42.

I'm hanging 1/2 inch cement board on both the sides and back of the chase going 6 feet up and was planning on just having insulation secured above that to the first firestop between the first and second floor.

Talking to a builder buddy of mine and he said it didn't matter if I used kraft backed insulation between thes studs and the cement board or if it was unfaced. This came about because I have had zero luck finding unfaced r13 insulation here in Indianapolis.

Given that the insulation will be exposed another three feet above the cement board line I'm looking for input on this (though I think I know the answer already).

there was NO insulation in the chase originally when I ripped out the old unit so I'm just making sure I'm doing this right once and for all.

You don't need to use the concrete board. Those ZC boxes can be
installed with 1/2" drywall in the chase, so why worry about the
Kraft facing on the insulation? I'd use faced R-19 & sheetrock the
interior all the way to the first first deck & be done with it. I would
make sure EVERY seam is sealed with caulk - acoustic caulk comes
in BIG tubes & works very well in this application. Make sure you lay
insulation on TOP of the firedeck, too, leaving clearance to the firestop...
I would also seal the firestop to the venting with aluminum tape to
prevent any cold air from above the firedeck entering the fireplace cavity.
Aluminum tape can be used to seal around your combustion air intake, as well...
I've have installed HUNDREDS of fireplaces this way - without safety
or code compliance issues.

 

[JeffT]

I've got the chase open and am finalizing prep for the z42.

I'm hanging 1/2 inch cement board on both the sides and back of the chase going 6 feet up and was planning on just having insulation secured above that to the first firestop between the first and second floor.

Talking to a builder buddy of mine and he said it didn't matter if I used kraft backed insulation between thes studs and the cement board or if it was unfaced. This came about because I have had zero luck finding unfaced r13 insulation here in Indianapolis.

Given that the insulation will be exposed another three feet above the cement board line I'm looking for input on this (though I think I know the answer already).

there was NO insulation in the chase originally when I ripped out the old unit so I'm just making sure I'm doing this right once and for all.

You don't need to use the concrete board. Those ZC boxes can be
installed with 1/2" drywall in the chase, so why worry about the
Kraft facing on the insulation? I'd use faced R-19 & sheetrock the
interior all the way to the first first deck & be done with it. I would
make sure EVERY seam is sealed with caulk - acoustic caulk comes
in BIG tubes & works very well in this application. Make sure you lay
insulation on TOP of the firedeck, too, leaving clearance to the firestop...
I would also seal the firestop to the venting with aluminum tape to
prevent any cold air from above the firedeck entering the fireplace cavity.
Aluminum tape can be used to seal around your combustion air intake, as well...
I've have installed HUNDREDS of fireplaces this way - without safety
or code compliance issues.

Excellent advice.I work alot of commercial jobs and have had problems with faced insulation but in your case I don't see an issue.

 

[ScotO]

I am finishing my chase here too. I used Roxul fireproof insulation between the studs and held it in place with metal retaining rods (in the insulation aisle at Lowes). My chase has several feet of clearance on either side of the ZC fireplace (I am installing a Napoleon NZ3000), and around a foot and a half clearance at the rear of the unit, so I am not going to use drywall. Just the retainers for the insulation. I will drywall the ceiling firestop and insulate that when I install the flue pipe. I already have that framed to the metal firestop requirements.

 

[DAKSY]

I am finishing my chase here too. I used Roxul fireproof insulation between the studs and held it in place with metal retaining rods (in the insulation aisle at Lowes). My chase has several feet of clearance on either side of the ZC fireplace (I am installing a Napoleon NZ3000), and around a foot and a half clearance at the rear of the unit, so I am not going to use drywall. Just the retainers for the insulation. I will drywall the ceiling firestop and insulate that when I install the flue pipe. I already have that framed to the metal firestop requirements.

You will be surprised just how much cold air penetration you will
get in your chase if you don't install drywall over the insulation.
That cold will find ways to create cold drafts around the firebox
& into the living space whether or not you have a fire burning.
That's why we ALWAYS install drywall over the faced insulation
ALL the way to the firedeck & seal ALL the seams with either acoustic
caulk or aluminum tape. In windier locations, I will tape every overlap
seam on the facing just for sh*ts & grins...You're not
gonna wanna hafta go back in there to make adjustments when you
find out that your wife/fiancee/girlfriend/significant other feels a cold
draft...I've been there. It took us a number of iterations before we came
up with this method & the resultant number of call backs for "cold" installs
has diminished down to NOTHING.
Your house - your call.

 

[Dad the Handyman]

You will be surprised just how much cold air penetration you will
get in your chase if you don't install drywall over the insulation.
That cold will find ways to create cold drafts around the firebox
& into the living space whether or not you have a fire burning.
That's why we ALWAYS install drywall over the faced insulation
ALL the way to the firedeck & seal ALL the seams with either acoustic
caulk or aluminum tape. In windier locations, I will tape every overlap
seam on the facing just for sh*ts & grins...You're not
gonna wanna hafta go back in there to make adjustments when you
find out that your wife/fiancee/girlfriend/significant other feels a cold
draft...I've been there. It took us a number of iterations before we came
up with this method & the resultant number of call backs for "cold" installs
has diminished down to NOTHING.
Your house - your call.

Wow, this is great information and exactly what I have been looking for. Can you tell me what you guys do to the floor when you install these? I was thinking of Durock for the floor to come up even with the level of the heart, which is level with the wood floor.

 

[DAKSY]

We set the firebox right on the subfloor. The very bottom of the Heat n Glo or Heatilator boxes have a vertical metal fascia that comes up about an inch from the bottom surface. With a 3/4 hearth (marble, granite, composite or whatever) the opening into the valve area above that fascia is STILL 1/4" +/- above that hearth.

 

[Dad the Handyman]

Thanks for the quick response. I have another question, that's not insulation related, so I'm not sure where to ask it, BUT...Since you are an installer of Zero Clearance...What do people generally do about creating access to the chase after the front stone/brick, etc. are on? My chase is running up through the attached garage, and that wall has to remain fire rated. The only thing I can think of is a fire-rated, insulated access door.

 

[DAKSY]

Thanks for the quick response. I have another question, that's not insulation related, so I'm not sure where to ask it, BUT...Since you are an installer of Zero Clearance...What do people generally do about creating access to the chase after the front stone/brick, etc. are on? My chase is running up through the attached garage, and that wall has to remain fire rated. The only thing I can think of is a fire-rated, insulated access door.

There should no need for access. Why would you want to get in there?

 

[Dad the Handyman]

I guess I was thinking that you would need to access it for inspection at some point, and possible chimney replacement down the road.