Is duct insulation considered a combustible

Stephen G Sheldon · 07-27-2009, 04:37 AM

In a crawl space the furnace vent passes along side and touches an insulated duct vent. Should I call this out or Is this acceptable?

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A.D. Miller · 07-27-2009, 05:50 AM

Originally Posted by Stephen G Sheldon

In a crawl space the furnace vent passes along side and touches an insulated duct vent. Should I call this out or Is this acceptable?

SS: Acceptable, though the slightest possibility exists for developing a "hot spot" in the vent at the pooint of contact with the insulation.

**Jerry Peck** · 07-27-2009, 07:06 AM

Originally Posted by Stephen G Sheldon

In a crawl space the furnace vent passes along side and touches an insulated duct vent. Should I call this out or Is this acceptable?

Originally Posted by A.D. Miller

SS: Acceptable, though the slightest possibility exists for developing a "hot spot" in the vent at the pooint of contact with the insulation.

Stephen,

NOT ACCEPTABLE.

Forget the part about being combustible or not, no insulation is allowed within the stated clearance either.

A.D. Miller · 07-27-2009, 07:15 AM

Originally Posted by Jerry Peck

Stephen,

NOT ACCEPTABLE.

Forget the part about being combustible or not, not insulation is allowed within the stated clearance either.

JP: Which part of the insulation in question is combustible at those termperatures?

**Jerry Peck** · 07-27-2009, 07:19 AM

Originally Posted by A.D. Miller

JP: Which part of the insulation in question is combustible at those termperatures?

Aaron,

Did you not read what I posted and you quoted?

Originally Posted by Jerry Peck

Forget the part about being combustible or not, not insulation is allowed within the stated clearance either.

**Bob Harper** · 07-27-2009, 08:19 AM

The duct wrap does not meet ASTM E-136 so therefore it should be treated as "combustible" inspite of our own personal perception of the material.

The insulation is not only invading in the stated clearance space but is in direct contact. This blocks the flow of cooling air and creates a hot spot.

The point where the insulation is in contact is obscured from normal inspection. A bad spot could develop there undetected. This is why the codes and stds. do not allow covers or wrapping of vent connectors. B-vent and L-vent, being listed systems with a proven track record are allowed as connectors even though their outer skin prevents direct visualization of the flue lining. You still must maintain the clearance to their outer skin per their listing.

Practically speaking, all that heat against that insulation may release either formaldehyde or phenol resins, both of which are nasty, stink and carcinogens.

The 'foil' scrim you see is actually FSK--foil scrim kraft, otherwise known as brown paper wrapped in tin foil. It carries a flame spread of 25 but IS combustible.

Should not be using single walled vent connector in a crawl space.

Any more pics?
Bob

A.D. Miller · 07-27-2009, 08:26 AM

Did you not read what I posted and you quoted?

JP: I did, but what does this mean?:not insulation is allowed within the stated clearance either

A.D. Miller · 07-27-2009, 08:30 AM

[quote=Bob Harper;93633]The duct wrap does not meet ASTM E-136 so therefore it should be treated as "combustible" inspite of our own personal perception of the material.

BH: As a fire espert you are certainly aware that anything is combustible with enough heat applied to it.

The insulation is not only invading in the stated clearance space but is in direct contact. This blocks the flow of cooling air and creates a hot spot.

BH: That is what I said.

The point where the insulation is in contact is obscured from normal inspection. A bad spot could delelop there undetected. This is why the codes and stds. do not allow covers or wrapping of vent connectors. B-vent and L-vent, being listed systems with a proven track record are allowed as connectors even though their outer skin prevents direct visualization of the flue lining. You still must maintain the clearance to their outer skin per their listing.

BH: Good point. Hadn't consdered that.

Practically speaking, all that heat against that insulation may release either formaldehyde or phenol resins, both of which are nasty, stink and carcinogens.

BH: Maybe.

**Jerry Peck** · 07-27-2009, 11:01 AM

Originally Posted by A.D. Miller

JP: I did, but what does this mean?:not insulation is allowed within the stated clearance either

Typo:

"not insulation is allowed within the stated clearance either"

Should be:

"no insulation is allowed within the stated clearance either"

Which means that if that is single wall - no insulation is allowed within the 6" minimum clearance.

For Type B gas vents that clearance is 1" with no insulation allowed within that clearance.