can foam insulation touch type B venting?

amakarevic

i have PVC pipe that comes to nearly the minimum legal distance from type B venting (1"). just to be safe, i was thinking of wrapping a couple of layers of that light blue insulation wrap that comes in 6" wide rolls. was wondering if that can come in contact with type B.

also, is type B allowed to come in contact with 2x4 framing?

thanks

brandonmcginnis

Mechanical code for B Vent requires a 1" clearance to combustibles. I'm pretty sure that wrap is considered a combustible. Leave it alone, it's not gonna hurt your PVC. Nothing should touch B Vent except metal straps or roof flashings.

amakarevic

but what can happen if it touches 2x4 ?

hvac122

A fire

amakarevic

come on... it NEVER gets that hot

Marty S.

Tell that to the inspector and see how far it gets you. Mechanical code states 1" minimum from combustibles for double wall flue and there are no exemptions.

Doc Holliday

No, never. And the furnace in my old home didn't do this, either...

sammy37

Dang Doc! What exactly happened?

amakarevic

did your furnace get caught on fire itself or the related venting? i am talking about venting here.

Doc Holliday

We'll never really know but that wood was so dry and brittle the firefighters spent 4 hours putting it out as it kept coming back. It could have been the flue pipe (I've seen burn marks on the rafters in homes where it has rested against the wood) or it could have been the motor or a wire or who knows.

All I know is I was renting that home (there for four months) and offered the HO my services up front in checking over the system and fixing it up, cleaning coils, patching air leaks, checking amperage, etc., in return for reduced rent for a few months and he declined, saying it was good enough as "it's worked fine all these years" and he couldn't afford to knock of rent. That system had been turned on in heating mode at night for two weeks prior but one night, after only about 20 minutes of it being on, it just went up in flames.

I sat and watched it burn for those four hours.

COLDIRON

1" all around live by that and keep living, it can get real hot if you have a heater running for long periods of time along with other appliances venting.

The 1" all around no touch was developed for a reason, FIRE.