Ventless fireplace and firestopping the attic

**JB Thompson** · 02-11-2016, 03:26 PM

Hello all,

While in the attic today, I could see all the way into the void behind the ventless heater.

Normally, I write the lack of firestopping especially when there is a prefabricated fireplace unit and chimney. However, the installation instructions for this unit were on site and did NOT say a word about blocking off the void to prevent fire extension into the attic.

There was also no requirement for the void to have sheetrock installed on the studs, so as you can see, everything is exposed in the photo.... even the lack of insulation.

There was a gap between the firebox and the brick lintel which, depending on what sort of flange/insulation is up there, could allow for a wayward fire to extend into this void.

So, I don't like it. But, the manufacturer doesn't seem to require the void to be sealed from the attic.

Any thoughts?

Similar Threads:

**Jerry Peck** · 02-11-2016, 03:53 PM

Originally Posted by JB Thompson

Normally, I write the lack of firestopping especially when there is a prefabricated fireplace unit and chimney. However, the installation instructions for this unit were on site and did NOT say a word about blocking off the void to prevent fire extension into the attic.

There was also no requirement for the void to have sheetrock installed on the studs, so as you can see, everything is exposed in the photo.... even the lack of insulation.

The code requires it whether or not the manufacturer's installation instructions do or not.

The code requires fireblocking at the floor and at the ceiling, and that means 'at the ceiling' you were standing on looking down into that chase.

Did you take a photo of, or write down, the manufacturer and model of that fireplace, I haven't seen one which did not require it to be fireblocked, but I have not (naturally) see them all, so there will always be someone to try to do things differently ... regardless, though, the code requires the fireblocking there.

**JB Thompson** · 02-11-2016, 07:56 PM

Originally Posted by Jerry Peck

The code requires it whether or not the manufacturer's installation instructions do or not.

The code requires fireblocking at the floor and at the ceiling, and that means 'at the ceiling' you were standing on looking down into that chase.

Did you take a photo of, or write down, the manufacturer and model of that fireplace, I haven't seen one which did not require it to be fireblocked, but I have not (naturally) see them all, so there will always be someone to try to do things differently ... regardless, though, the code requires the fireblocking there.

OK, I was looking at this all wrong. I assume you're referring to 302.11. And it doesn't matter what is down in that chase. Thanks.

**John Kogel** · 02-11-2016, 10:30 PM

Thanks, JP. I was thinking the same thing - the maker of a ventless fireplace is hardly an authority on fire safety, or air quality either, for that matter.

**ROBERT YOUNG** · 02-12-2016, 02:51 AM

JB just curios, was the masonry, specifically the mortar bed, head and but joints in good shape? The ooze was runny leaving water staining on the back of the brick. Poor batch and usually refused by the masons. How old was the build?

**JB Thompson** · 02-12-2016, 06:47 AM

Originally Posted by ROBERT YOUNG

JB just curios, was the masonry, specifically the mortar bed, head and but joints in good shape? The ooze was runny leaving water staining on the back of the brick. Poor batch and usually refused by the masons. How old was the build?

Seemed ok. House was built in 2010

**Bob Harper** · 02-12-2016, 05:10 PM

Most any mfr. will include instructions to install to the code, which is the catchall for picking up the need for fireblocking as JP pointed out.

You have insulation on top of the firebox, which must be removed as it constitutes fire hazard.

The gap in the first photo is a severe fire hazard. Since this is a VF, ALL the heat will pass this point. The gap will act like a chimney and channel heat directly to that combustible header which will pyrolyze and ignite. Not only must this be sealed but if this Fp has been run then it should get a level III internal inspection to ensure the header isn't already pyrolyzed before sealing the gap.
That CSST is not installed properly and cannot lay against the hot fireplace.

The outer wall would need to be weatherized per the code then sheathed over with drywall or other sheathing such as T-ply. You don't have to sheath the entire chase interior and it does not have to be type X. It just has to meet the energy code and have a flame spread of 500 or less.

**ROBERT YOUNG** · 02-13-2016, 12:18 AM

Originally Posted by Bob Harper

Most any mfr. will include instructions to install to the code, which is the catchall for picking up the need for fireblocking as JP pointed out.

1: You have insulation on top of the firebox, which must be removed as it constitutes fire hazard.

The gap in the first photo is a severe fire hazard. Since this is a VF, ALL the heat will pass this point. The gap will act like a chimney and channel heat directly to that combustible header which will pyrolyze and ignite. Not only must this be sealed but if this Fp has been run then it should get a level III internal inspection to ensure the header isn't already pyrolyzed before sealing the gap.
That CSST is not installed properly and cannot lay against the hot fireplace.

The outer wall would need to be weatherized per the code then sheathed over with drywall or other sheathing such as T-ply. You don't have to sheath the entire chase interior and it does not have to be type X. It just has to meet the energy code and have a flame spread of 500 or less.

Bob, you touched upon a lot of safety issues.
Insulation, CSST, fire block.
The fire block is a concern, builders defect, and a consensus among the colleagues.

Fiberglass insulation on the other hand has not been mentioned...
Before I post a link, that is contrary to you remarks, would it not be best to know the manufacturer gas appliance, a tag or model number, UL label, and that specific models clearance rating prior to any recommending?

From CeertainTeed.
CertainTeed Case Studies / Articles: Insulation
Fire resistance
Made from sand and recycled glass, fiber glass insulation is naturally noncombustible and remains so for the product's life. It requires no additional fire-retardant chemical treatments. Many building codes also recognize fiber glass insulation as an acceptable fire stop in wood- and steel-framed wall assemblies.
Case Study Detail - CertainTeed

**Bob Harper** · 02-13-2016, 01:02 PM

Originally Posted by ROBERT YOUNG

Bob, you touched upon a lot of safety issues.
Insulation, CSST, fire block.
The fire block is a concern, builders defect, and a consensus among the colleagues.

Fiberglass insulation on the other hand has not been mentioned...
Before I post a link, that is contrary to you remarks, would it not be best to know the manufacturer gas appliance, a tag or model number, UL label, and that specific models clearance rating prior to any recommending?

From CeertainTeed.
CertainTeed Case Studies / Articles: Insulation
Fire resistance
Made from sand and recycled glass, fiber glass insulation is naturally noncombustible and remains so for the product's life. It requires no additional fire-retardant chemical treatments. Many building codes also recognize fiber glass insulation as an acceptable fire stop in wood- and steel-framed wall assemblies.
Case Study Detail - CertainTeed

It doesn't matter what make or model. NO gas fireplace is tested or listed with insulation or any other foreign matter lying on top or in contact with it. They are boxed in with 3/4" plywood painted flat black and the seams taped. Thermocouples are mounted in a grid of 6" squares and at key points then the tests run. When you place a blanket over yourself in bed at night what is the effect? You get warmer. Same with the fireplace. These areas need to be left bare so air can strip away heat. When you have insulation or even concrete lying over these areas, the heat signature of the box rises considerably. Trust me--I've worked in an R&D test lab and I investigate fire losses.

As for fiberglass being "non-combustible", we look to NFPA for the definition, which, for a mfd. product points to passing ASTM E-136, which fiberglass cannot pass. That's for unfaced batts or loose fill. With regards to this case where we have unfaced batts, these do not meet the energy code so they would need to be replaced with Kraft paper faced batts properly installed then sheathed over to prevent them from falling onto a hot object. Yes, the IRC lists fiberglass as one choice for fireblocking. So is drywall. That does not make it Superman's cape.

The insulation on top of the fireplace must go and the exterior stud cavities should be redone to the energy code regardless of make and model. Does that address your concerns Robert?

**ROBERT YOUNG** · 02-13-2016, 01:56 PM

Originally Posted by Bob Harper

It doesn't matter what make or model. NO gas fireplace is tested or listed with insulation or any other foreign matter lying on top or in contact with it. They are boxed in with 3/4" plywood painted flat black and the seams taped. Thermocouples are mounted in a grid of 6" squares and at key points then the tests run. When you place a blanket over yourself in bed at night what is the effect? You get warmer. Same with the fireplace. These areas need to be left bare so air can strip away heat. When you have insulation or even concrete lying over these areas, the heat signature of the box rises considerably. Trust me--I've worked in an R&D test lab and I investigate fire losses.

As for fiberglass being "non-combustible", we look to NFPA for the definition, which, for a mfd. product points to passing ASTM E-136, which fiberglass cannot pass. That's for unfaced batts or loose fill. With regards to this case where we have unfaced batts, these do not meet the energy code so they would need to be replaced with Kraft paper faced batts properly installed then sheathed over to prevent them from falling onto a hot object. Yes, the IRC lists fiberglass as one choice for fireblocking. So is drywall. That does not make it Superman's cape.

The insulation on top of the fireplace must go and the exterior stud cavities should be redone to the energy code regardless of make and model. Does that address your concerns Robert?

No concerns Bob.
Simple questions about fiberglass, in this case, loose file.

I have heard the back and forth about fiberglass and you answered that.
I do not assess using ASTM so I will leave it at that.
I am sure a fire break will do the job.

My question about manufacturers' model.
Now about; The term Zero Clearance.
In particular, a fireplace can be enclosed using combustible materials.

From Napolean; These combustible building materials may allowed to be installed against the body of the fireplace without fear of combustion or heat damage. However, some fireplaces may require installation using non-combustible materials such as metal studs and framing for the parts of the enclosure in the immediate vicinity of the fireplace. Please have a professional install your fireplace following the parameters presented in the installation instructions to ensure that it is installed using the correct materials.

Would you be able to provide me with a clarification?

**Bob Harper** · 02-14-2016, 09:35 AM

Originally Posted by ROBERT YOUNG

No concerns Bob.
Simple questions about fiberglass, in this case, loose file.

I have heard the back and forth about fiberglass and you answered that.
I do not assess using ASTM so I will leave it at that.
I am sure a fire break will do the job.

My question about manufacturers' model.
Now about; The term Zero Clearance.
In particular, a fireplace can be enclosed using combustible materials.

From Napolean; These combustible building materials may allowed to be installed against the body of the fireplace without fear of combustion or heat damage. However, some fireplaces may require installation using non-combustible materials such as metal studs and framing for the parts of the enclosure in the immediate vicinity of the fireplace. Please have a professional install your fireplace following the parameters presented in the installation instructions to ensure that it is installed using the correct materials.

Would you be able to provide me with a clarification?

The hearth industry has been fighting the use of that stupid term "Zero clearance fireplace" since it first came out in the '50s. Virtually ALL factory built fireplaces are rated for a zero clearance to a combustible floor. Some allow the jack studs to contact on the sides while others state a clearance of 1/2"-1" except for the nailing flanges. Again, you can allow the tips of the vee stand-offs at zero clearance but not the top of the box itself. If someone has tested and listed a factory built fireplace to which they claim you can place combustibles directly in contact with the entire box then it is an anomaly as 99.9999999999999% of the rest of the industry requires some clearance off most of the box except the base. Metal studs are problematic since they conduct so much heat. As for the nailing flanges, they conduct a LOT of heat. If you look at several different types of factory built fireplaces side by side you'll see some have upper nailing flanges rather high on the box, some maybe 6-8" down from the top and some with a continuous flange. The continuous flange box runs the coolest and the one with the flanges down runs the hottest. It's all determined by testing. You start at the top and keep moving the flanges down until it passes. Same for clearances. You construct the box and fire it, then as it fails, you add strips of wood to the box expanding it and the clearance until it passes. It varies with each box model.

I strongly recommend everyone purge that term "zero clearance fireplace" from their lexicon and substitute "factory built fireplace". HTH

**ROBERT YOUNG** · 02-14-2016, 07:46 PM

Originally Posted by Bob Harper

The hearth industry has been fighting the use of that stupid term "Zero clearance fireplace" since it first came out in the '50s. Virtually ALL factory built fireplaces are rated for a zero clearance to a combustible floor. Some allow the jack studs to contact on the sides while others state a clearance of 1/2"-1" except for the nailing flanges. Again, you can allow the tips of the vee stand-offs at zero clearance but not the top of the box itself. If someone has tested and listed a factory built fireplace to which they claim you can place combustibles directly in contact with the entire box then it is an anomaly as 99.9999999999999% of the rest of the industry requires some clearance off most of the box except the base. Metal studs are problematic since they conduct so much heat. As for the nailing flanges, they conduct a LOT of heat. If you look at several different types of factory built fireplaces side by side you'll see some have upper nailing flanges rather high on the box, some maybe 6-8" down from the top and some with a continuous flange. The continuous flange box runs the coolest and the one with the flanges down runs the hottest. It's all determined by testing. You start at the top and keep moving the flanges down until it passes. Same for clearances. You construct the box and fire it, then as it fails, you add strips of wood to the box expanding it and the clearance until it passes. It varies with each box model.

I strongly recommend everyone purge that term "zero clearance fireplace" from their lexicon and substitute "factory built fireplace". HTH

Thank you Bob.
I would enjoy any material you would have to offer.
Best regards.
Robert