Draft/Fire Stop Foam Rated for Contact w/Flue Pipes?

**Nick Ostrowski** · 03-27-2009, 07:28 AM

Does anybody know if the orange draft/firestopping foam is rated as being OK for direct contact with type-B flue pipes?

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**Jerry Peck** · 03-27-2009, 07:32 AM

Originally Posted by Nick Ostrowski

Does anybody know if the orange draft/firestopping foam is rated as being OK for direct contact with type-B flue pipes?

Yes, I know that no insulation is allowed to be in contact with Type B Gas Vents.

Not just for the insulation, it is for the vent.

Bob Harper can explain it better than I can (because what I know about it I learned mostly from him

).

However, I also do not see a support strap for that elbow where it turns up.

**Wayne Carlisle** · 03-27-2009, 07:39 AM

Originally Posted by Jerry Peck

However, I also do not see a support strap for that elbow where it turns up.

Sure there is Jerry! Can't you see the romex in the backgound?

On another thought on the "orange junk". Isn't that the type of sealant that expands with heat? If so would there be a possibility that it would expand unecessarily? Or is the rating so high before activation that the b-vent doesn't get that hot?

**Nick Ostrowski** · 03-27-2009, 07:55 AM

Yes, it is OK.......or......Yes, it is not OK?.

If I recall correctly, something about anything being in contact with the pipe may create a hot spot because air can't flow around that flue pipe section and dissipate heat?

There were straps on the flue pipe Jerry. They are just out of the picture to the right.

**Jerry Peck** · 03-27-2009, 08:24 AM

(red bold text is mine)

Originally Posted by Jerry Peck

Yes, I know that no insulation is allowed to be in contact with Type B Gas Vents.

Originally Posted by Nick Ostrowski

Yes, it is OK.......or......Yes, it is not OK?.

Yes, it is NOT okay.

If I recall correctly, something about anything being in contact with the pipe may create a hot spot because air can't flow around that flue pipe section and dissipate heat?

Yep, something like that.

**Nick Ostrowski** · 03-27-2009, 08:30 AM

Thanks Jerry.

Robert Olson · 03-27-2009, 12:00 PM

It's not insulation, it looks like Hilti fire stop and is approved for contact with B vent and fire blocking. It's red on application and turns orange as it ages.
Firestop Systems - hilti.com

**Jerry Peck** · 03-27-2009, 07:13 PM

Originally Posted by Robert Olson

It's not insulation,

Sure looks like that expanding foam to me.

it looks like Hilti fire stop and is approved for contact with B vent and fire blocking. It's red on application and turns orange as it ages.
Firestop Systems - hilti.com

The Hilti stuff *may* be approved for use in contact with Type B gas vent, but the Type B gas vent *is not* approved to have that around it.

I've seen and used that firestop stop before, and it does not look like that, and its purpose was not for that use either. Firestop products MUST be installed in accordance with proper firestop designs, it is not "firestop" when just applied as caulking around a Type B gas vent at a thin metal firestop plate - not unless there is a design which was approved for its use there (and any construction requiring firestopping for a Type B gas vent would have the vent in a shaft, which would be the firestopping, and the vent would not be firestopped as shown, would not be any need to, the shaft is the separation and firestop.

**Bob Harper** · 03-27-2009, 07:13 PM

Robert, that link is only to Hilti's entire product line, which narrows it down to about 50,000 items. Can you be a little more specific about which Hilti product you are referencing? Thx

In general, you cannot seal any listed firestop unless it is permitted by the listing and the product is specified. For instance, If you seal the listed firestops on air cooled factory built wood burning fireplaces, you stop cooling the chase, which raises temps. and voids the listing. Some gas fireplaces, such as Heatilator, Heat&Glo, Quadrafire actually have tested their firestops caulked with 300*F rated RTV silicone and approved it. What they did not approve is a big blob of 'stuff' at the firestop where, as Nick mentioned, you will raise the temps. and threaten your clearances. You also need to be concerned with odors and off-gassing.

I recommend as an inspector, you record the make, model and serial number of the appliance, mfr. and model of the venting and contact the mfr.s. In the case with a B-vented gas fireplace, I would contact both mfrs. If they say no but the caulking mfr., such as Hilti approve it, then there is a transfer of liability to Hilti or an assumption of the risk on their part and that of the installer. This becomes a problem in commercial work where you exceed three floors and come under the IBC and have fire rated assemblies. In general, they want to see firestops listed to UL 814 for the hose stream test. Again, contact the mfrs.

HTH,
Bob