would this be wrong

bennythepitbull

being that Heat is the force that provides a

strong draft  and I want to be careful to minimize any heat loss in the vent.

I am wondering would it be wrong or against a code to use fiberglass insulation to further insulate the horizontal run of a type B vent?

Brad White

I would not

for a couple or reasons. B-vent is listed for, I believe, 12 inches clearance to combustibles. (EDIT Correction, 1-inch to combustibles but 12 inches per NFPA 211; most B-Vent is listed for 1-inch.) While fiberglass is not combustible, per se, it often has a facing which is. That would fall within the 12 inches, insulated or not. Also to insulate it at all, I would ask the manufacturer or browse their literature to see if it violates the listing. I suspect that it does because, as a system, there are certain assumptions for heat dissipation which insulation would violate.



Secondly, if you do have a draft problem (I have to assume so as that is the initial driver of your question), are you masking the symptoms while ignoring the cause?



Yes, heat, or rather the difference in temperature is one of the stronger drivers in stack draft, but do not forget height, wind velocity, indoor/outdoor pressure differences, etc. If you have a draft issue, seek out why first. And if draft cannot be improved passively by good practice or too long of a horizontal run versus your rise, a listed draft inducer may be necessary.



May I also add that any leakage or condensation would be masked by the insulation. I want to see the surface. May just be a chimney rain leak, but any corrosion? I need to know.



So no, insulating would be the last thing I would consider doing.



My $0.02



Brad

bennythepitbull

thanks

I do not have a draft problem it works rather well, the title of this forum is never be too safe that is why I am asking. i did think of the water leak issue. in addition i just want the lateral which would be the highest heat loss to be insulated. I was considering using foil sided insulation. BTW B vent only requires 1" clearance. MY thought was my near boiler steam pipes are even hotter then the b vent and it is allowed to cover them with fiber glass.  I suppose i should just leave well enough alone i thank u for the input.

bennythepitbull

duhh !

13.   Can I wrap B Vent with insulation?



No, B Vent cannot be wrapped with insulation





per http://www.duravent.com/?page=faqs/bvent2.php











there u have it

Tim McElwain

The clearance from

combustibles for "B" vent is 1" for single wall six inches. The fact that the horizontal run is "B" vent is already giving you the best venting situation as the difference in heat loss between single wall vent and double wall is quite a bit.



I do not recommend single wall pipe on any installations anymore as the flue losses on equipment today are so low the single wall can't support drafting all the time.



The problem with insulating the "B" vent by the way is that the maximum  operating temperature of "B" vent is 550 degrees and insulating it may cause it to exceed its temperature rating and begin to melt down.

Brad White

Tim

I too always subscribed to the 1" clearance from combustibles, but NFPA-211 does not recognize less than 12 inches even with a guarded air space. Granted the UL listing and NFPA are different standards and neither is code unless stipulated as a referenced standard in a jurisdictions codes.



There was one manufacturer who also had the clearances at 12 inches, which would put them at a competitive disadvantage.  But most others as you say, have it at 1" so I stand corrected. 

Tim McElwain

Most manufacturers

list "B" vent as 1" clearance so I assume that is because they have been tested and found to be safe at that distance. I do not have my NFPA 211 in my home office it is at the training center so I will have to take a look at it When I am there.



By the way clearances on single wall old Class C with conversion burners is 9". You can't use "B" vent with most conversion burners although I have started to see some specs from newer power gas conversion burners list it as a venting choice.

bennythepitbull

thank for the info all

I see know that it would cause the B vent to get too hot



I have a question :I know there is a smoke I can use to see how my draft is working.



but i do not know what it is called. I would settle for something simple.

Brad White

Chemical Smoke

I am not certain what would be used specifically for combustion draft smoke, I will leave that to the pros in the field.



For building diagnostics, I use a chemical pen or puffer which uses titanium tetrachloride. This produces a dense, white smoke when it contacts moisture in the air. However, the slight residue is corrosive, (hydrochloric acid), so I have my doubts in principle around combustion, even if it is "up the chimney".



Another means uses propylene glycol passed over a hot wire. The smoke is practically as dense and sweet-smelling. I think that this is more benign. But I am also curious what is actually used.



That said, the path that smoke takes only tells you qualitatively what is going on. The best indicator is a draft gauge (manometer), which gives you a repeatable value in pressure.

Tim McElwain

If all you want

is to check and see if the vent/chimney is pulling just a match held at the opening to the draft hood will tell you if it is pulling.



Much better however to test with a draft gauge to insure accurate -.01" W.C., -.02 W.C.or -.03 W.C. for draft. You should check draft on both sides of the draft hood or barometric. I am assuming here that this system you are talking about is gas as you called the vent "B" vent. "B" vent is a gas vent only.



We are however getting into things which require a professional with training on combustion.