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MN Renovator · 11-15-13, 09:39 AM

I know that spray foam is generally considered to be combustible even when cured but I figured that Dow Great Stuff™ Fireblock foam would be a little harder to ignite than it is.

I didn't put much thought to it and I've been using it since it is available and figured that most people that I've talked to and most online sites about conservation say to use spray foam and don't generally display a concern for fire safety in its use. I figured that this fireblock foam was a better option than the standard stuff, but after playing with it, I'm not sure I'll be paying the extra expense anymore.

I figured I'd need a torch to light the stuff but when I took it outside on the concrete front step, it took about two seconds of contact with the flame of a common butane lighter and it was lit and continued to burn unaided when the lighter was removed.

Here are the points that I figure that people are sold on:
Impedes spread of fire and smoke through service penetrations
Recognized as an Alternate Fireblocking material for residential construction
Tested according to ASTM E84, ASTM E814 (modified), UL 1715
Bright orange colored foam for easy code identification

The only understanding that I have is that the idea of preventing air movement could prevent flame spread.

Here is part of a statement from Dow in response to someone's online review of this product.
"GREAT STUFF (TM) Insulating Foam Sealant products should not be used around heaters, furnaces, fireplaces, or recessed lighting fixtures where it contacts heat conducting surfaces. Cured foam is combustible and may present a fire hazard if exposed to flame or temperatures above 240F."
and
"GREAT STUFF™ FireBlock Insulating Foam Sealant is a minimal-expanding, single-component foam sealant for general purpose building envelope air sealing. This product is defined by the International Building Codes as the use of approved building materials installed in concealed spaces to resist the migration of fire and hot gases. GREAT STUFF™ FireBlock is tinted orange to be more recognizable to building code officials. This product is not approved for use in firestop systems. The Dow Chemical Company makes the GREAT STUFF™ products, if you are looking for other material other than GREAT STUFF™, please refer to 3M’s website."

I added the bold above instead of just posting a partial quote the second statement to keep it in context.

My point is that this product is not an intumescent firestop like some spray foams or encapsulants for spray foams can be. The can does say "Residential Fireblock Penetration Sealant". It also has flame spread characteristics but I don't know what those numbers mean but figured they were numbers that indicated that it was not very flammable. I think that 'FireBlock' is a little bit deceiving as it seems very similar in name to firestop, which is something Dow says its not. Although when looking at the can it doesn't say that it isn't a firestop. The part that says "Flammable. Avoid sources of ignition, open flame, temps above 240f (116c). Pressurized. Can may burst. Do not punture or incinerate. Avoid temps above 120f (49c)." suggested to me that this was when applying the product due to the flammable nature of the propellants used in spray foam.

Why am I posting this thread?
I have seen others on this forum either mentioning its use(and at least one picture) to seal up the knockout penetrations for wires around junction boxes such as light switch boxes, electrical outlet boxes, and light fixture junction boxes. A junction box is designed to be a fire resistant container designed to contain most short circuit arcing(such as bad twist-on wire connections) and overloads until the circuit breaker or fuse blows. They are a specific size, thickness, and material to contain a certain amount of heat. It's my opinion that the knockouts should be sealed, especially when these are covered in insulation in an attic and that heat or arcing would otherwise contact the insulation along with the air sealing needs for conservation.

I personally use a fire rated caulking UL 1479 rated for filling the air gaps in the attic facing junction box knockouts. I think spray foam is just fine in places other than electrical junction boxes and combustion venting, since it is then behind drywall or other fire rated materials in the same area that other materials that burn are located such as wood framing for example. A UL 1479 fire-rated product similar to this is what I think is ideal for electrical junction box air sealing. DAP Fire Stop 10.1 oz. Silicone Sealants (2-Pack)-181244 at The Home Depot I actually used a White Lightning based UL 1479 product but I can't find the same product(their UL 1479 stuff) anymore.

Thoughts?

11-15-13, 09:39 AM	#1
MN Renovator Less usage=Cheaper bills Join Date: Nov 2010 Location: Minneapolis, MN Posts: 939 Thanks: 41 Thanked 116 Times in 90 Posts	Fireblock foam burns I know that spray foam is generally considered to be combustible even when cured but I figured that Dow Great Stuff™ Fireblock foam would be a little harder to ignite than it is. I didn't put much thought to it and I've been using it since it is available and figured that most people that I've talked to and most online sites about conservation say to use spray foam and don't generally display a concern for fire safety in its use. I figured that this fireblock foam was a better option than the standard stuff, but after playing with it, I'm not sure I'll be paying the extra expense anymore. I figured I'd need a torch to light the stuff but when I took it outside on the concrete front step, it took about two seconds of contact with the flame of a common butane lighter and it was lit and continued to burn unaided when the lighter was removed. Here are the points that I figure that people are sold on: Impedes spread of fire and smoke through service penetrations Recognized as an Alternate Fireblocking material for residential construction Tested according to ASTM E84, ASTM E814 (modified), UL 1715 Bright orange colored foam for easy code identification The only understanding that I have is that the idea of preventing air movement could prevent flame spread. Here is part of a statement from Dow in response to someone's online review of this product. "GREAT STUFF (TM) Insulating Foam Sealant products should not be used around heaters, furnaces, fireplaces, or recessed lighting fixtures where it contacts heat conducting surfaces. Cured foam is combustible and may present a fire hazard if exposed to flame or temperatures above 240F." and "GREAT STUFF™ FireBlock Insulating Foam Sealant is a minimal-expanding, single-component foam sealant for general purpose building envelope air sealing. This product is defined by the International Building Codes as the use of approved building materials installed in concealed spaces to resist the migration of fire and hot gases. GREAT STUFF™ FireBlock is tinted orange to be more recognizable to building code officials. This product is not approved for use in firestop systems. The Dow Chemical Company makes the GREAT STUFF™ products, if you are looking for other material other than GREAT STUFF™, please refer to 3M’s website." I added the bold above instead of just posting a partial quote the second statement to keep it in context. My point is that this product is not an intumescent firestop like some spray foams or encapsulants for spray foams can be. The can does say "Residential Fireblock Penetration Sealant". It also has flame spread characteristics but I don't know what those numbers mean but figured they were numbers that indicated that it was not very flammable. I think that 'FireBlock' is a little bit deceiving as it seems very similar in name to firestop, which is something Dow says its not. Although when looking at the can it doesn't say that it isn't a firestop. The part that says "Flammable. Avoid sources of ignition, open flame, temps above 240f (116c). Pressurized. Can may burst. Do not punture or incinerate. Avoid temps above 120f (49c)." suggested to me that this was when applying the product due to the flammable nature of the propellants used in spray foam. Why am I posting this thread? I have seen others on this forum either mentioning its use(and at least one picture) to seal up the knockout penetrations for wires around junction boxes such as light switch boxes, electrical outlet boxes, and light fixture junction boxes. A junction box is designed to be a fire resistant container designed to contain most short circuit arcing(such as bad twist-on wire connections) and overloads until the circuit breaker or fuse blows. They are a specific size, thickness, and material to contain a certain amount of heat. It's my opinion that the knockouts should be sealed, especially when these are covered in insulation in an attic and that heat or arcing would otherwise contact the insulation along with the air sealing needs for conservation. I personally use a fire rated caulking UL 1479 rated for filling the air gaps in the attic facing junction box knockouts. I think spray foam is just fine in places other than electrical junction boxes and combustion venting, since it is then behind drywall or other fire rated materials in the same area that other materials that burn are located such as wood framing for example. A UL 1479 fire-rated product similar to this is what I think is ideal for electrical junction box air sealing. DAP Fire Stop 10.1 oz. Silicone Sealants (2-Pack)-181244 at The Home Depot I actually used a White Lightning based UL 1479 product but I can't find the same product(their UL 1479 stuff) anymore. Thoughts? Last edited by MN Renovator; 11-15-13 at 09:43 AM..