Chase design questions

[M1_Mission]

Hello,

Please forgive my ignorance in all things fireplace related...

I recently purchased a home and had the Heat & Glow SL-550TRS-C fireplace inspected.

The inspector identified a few issues.

The main issue is that the back side of my fireplace, is entirely in my garage and there is no chase built to house the fireplace and exhaust duct.

I have the owners manual and intend to follow the clearance requirements to combustible materials. I have lots of experience with construction and DIY projects. However, I have never dealt with fireplaces and am a little apprehensive to build something that is potentially going to start on fire and burn my house down.

After hours of google searches, i cannot find clear and concise instructions on how to properly construct a chase.

Can someone please spell it out for me like I am a small child? lol

I.e., Do both sides of the chase walls have to be sheetrocked? What type of insulation is used that near a fireplace? The side and back clearance to combustible material is .5". I understand what that means, but is it actually safe to have sheetrock .5" away from the the fireplace? Any information that can be used in chase design and construction will help tons.

I will post some photos later this evening.

Any feedback is greatly appreciated.

Thanks,

Adam

 

[M1_Mission]

Here are some pictures before and after I removed the sheet metal tape and trimmed the Sheetrock to meet the clearance requirements.

 

[DAKSY]

Here is the installation manual for your unit. Take a look at it & if anything is unclear post your questions.

 

[M1_Mission]

Thank for your reply. I have reviewed the manual and have trimmed all the Sheetrock accordingly.

One of my many questions is when I frame out the chase, is the interior sheet rocked as well?

Is it safe to have Sheetrock .5” away from the fireplace even though my distance to combustible material is .5”?

If I don’t Sheetrock the inside the chase, is the insulation safe?

What type of insulation do I need?

Thanks in advance,

Afam

 

[begreen]

The chase is basically just a framed box enclosing the stove and flue. The protects the unit and also protects people from accidentally touching it. If the clearances are honored it should be safe. There is no harm in exceeding clearances and often it's a good idea for peace of mind. Note that the flue pipe has different clearance requirements.

The chase doesn't have to have insulation, but it may be desired to keep the cold from entering the house. If so, string wire in an X fashion in each stud bay in order to keep the stove--side of the insulation in place. The chase does not need a sheetrock liner but that is recommended to create a sealed interior of the chase to block breezes and cold air infiltration. Check with the inspector to see what local code requires.

 

[Lennox65]

The pictures below are from a rear vent fireplace in an exterior chase. While your application is somewhat different, the principles are the same. As others have said, make sure that you keep the proper clearances from the fireplace and venting( as specified in the installation manual).

 

[M1_Mission]

I just purchased thermafiber F15. After I got home I realized the packaging says do not use insulation in spaces around metal chimneys, fireplaces or flues.

I will return it.

If I cannot use fire rated mineral wool, What type of insulation can I use?

 

[Lennox65]

Do the instructions say do not pack or fill around chimneys? As long as you have the proper clearance from the fireplace and flue, you should be able to use that in-between the studs(provided that the thickness of the insulation is not greater than the depth of the framing). It needs to be fixed in place so that it does not fall on the fireplace or flue.

The clearances are for air space and many people think that non combustible insulation can be placed against the fireplace or flue. This is incorrect and will cause a fire.

 

[begreen]

That's correct. The insulation should not contact the insert or the flue pipe.

Regular fiberglass insulation can be used with the paper side facing the garage interior away from the ZC insert. In mineral wood, Roxul brand batts are ok.

 

[M1_Mission]

I really appreciate the information.

I will be maintaining the proper clearance to combustibles. I just wasn’t sure if the insulation I bought is appropriate since it says not to be used in fireplaces. Even though it is fire rated rock wool.

Due to clearance issues. I have to frame the chase out with 2x3. The insulation is 3.5 inches thick. I plan to line the inside wall with chicken wire and then trim the insulation down an inch so the exterior Sheetrock doesn’t smash it so much.

Thoughts?

 

[M1_Mission]

@Lennox65, the clearance for the second 45 joint is going to be right at the .5" limit of acceptable clearance to combustible material.

Is it permissible to fashion a sheet metal shield in the stud bay to help protect the rockwool?

Or is this just going to heat up the wool and become an even more unsafe area?

Thanks for all your help.

 

[Lennox65]

@Lennox65, the clearance for the second 45 joint is going to be right at the .5" limit of acceptable clearance to combustible material.

Is it permissible to fashion a sheet metal shield in the stud bay to help protect the rockwool?

Or is this just going to heat up the wool and become an even more unsafe area?

Thanks for all your help.

The pipe actually needs 1" clearance on all sides when it is vertical. It needs 3" clearance above and 1" clearance on the sides and bottom when being run horizontally.

Covering a combustible with metal does not reduce the clearances or make the combustible material non combustible.

 

[M1_Mission]

Understood. Sorry I was thinking of the .5" clearance from the Sides and back of the actual fireplace.

So to be clear, I gain nothing by installing a piece of Sheetmetal in the stud bay nearest the duct 45?

I would have thought it acted as some sort of heat sink and would help to dissipate the heat on from the pipe.

 

[begreen]

@Lennox65, the clearance for the second 45 joint is going to be right at the .5" limit of acceptable clearance to combustible material.

By duct, so you mean the flue (exhaust) pipe? Flue pipe has a different clearance. Check this. It's either 1" or 2". Check the manufacturer's requirements. While the metal will block radiant heat it still gets hot. A sheetmetal guard without an airspace between it and the combustible does not work. Metal is a good conductor of heat. It's the 1" air gap that is the insulator.

I'm not following why the chase bumpout into the garage can't be made an inch or two deeper to eliminate any close spots.

 

[M1_Mission]

By duct, so you mean the flue (exhaust) pipe? Flue pipe has a different clearance. Check this. It's either 1" or 2". Check the manufacturer's requirements. While the metal will block radiant heat it still gets hot. A sheetmetal guard without an airspace between it and the combustible does not work. Metal is a good conductor of heat. It's the 1" air gap that is the insulator.

I'm not following why the chase bumpout into the garage can't be made an inch or two deeper to eliminate any close spots.

Thank you for your response.

It totally can be built differently to ensure proper clearance to combustibles.

I was hoping to be able to frame out the chase following the shape of the box that was built for the fireplace to sit on. Doing this requires 2x3s, leaving 2” to the fireplace on each side and almost exactly and in the to the flue pipe where it makes its 2d 45 turn.

Not a big deal to enlarge the dimensions. It’s actually proving to be much more complicated trying to meet all the clearance requirements this way.

I guess the worst part about enlarging it is cutting the dry wall back to install blocking to tie the new frame to.