Insulation Vapor barrier on Garn

[Sawyer]

After reading Rick's post and others about overheating and steam I have a question. How do you handle the vapor barrier between the rear of the Garn and the outside cold wall? The manual says combustible materials must be at least 2" from the chimney. If there is not a vapor barrier, wouldn't the fiberglass become saturated at the outside wall due to condensation? Wouldn't this would cause problems with rotting as well as R-Values?

 

[Frozen Canuck]

You should have an adequately sized metal heat shield (I prefer using a larger shield than is the minimum required by code as this is very cheap insurance) around the chimney where it passes through the wall (both on interior & exterior) just as you would have one in the ceiling & another in the roof if you had a vertical chimney. Your plastic vapor barrier overlaps slightly on the edge of the heat shield & continues on from there, use an approved seam tape or approved tube contained product to join the two together at the edge of the heat sheild. BTW fiberglass will not be approved for use against the chimney, you will need to use a rated fireproof insulation such as a Rocksul product or equivalent around the chimney penetration through the wall. Hope this helps.

 

[Sawyer]

You should have an adequately sized metal heat shield (I prefer using a larger shield than is the minimum required by code as this is very cheap insurance) around the chimney where it passes through the wall (both on interior & exterior) just as you would have one in the ceiling & another in the roof if you had a vertical chimney. Your plastic vapor barrier overlaps slightly on the edge of the heat shield & continues on from there, use an approved seam tape or approved tube contained product to join the two together at the edge of the heat sheild. BTW fiberglass will not be approved for use against the chimney, you will need to use a rated fireproof insulation such as a Rocksul product or equivalent around the chimney penetration through the wall. Hope this helps.

Thanks, I will get tape tomorrow.
Direct contact with unfaced fiberglass on the Duravent chimney is approved by Garn. I was concerned so I checked with Duravent and they said Garn does its own testing to their specifications for UL and other approvals. In fact they said they do not approve a horizontal chimney and Garn had to get their own approval.

 

[Frozen Canuck]

Yes, understood. I was refering to your local building code as a violation of that code will give your insurance company an instant out if there were to ever be a claim.

 

[Sawyer]

Yes, understood. I was refering to your local building code as a violation of that code will give your insurance company an instant out if there were to ever be a claim.

Good point! My insurance company approved the installation as per Garn's installation manual. I will check with them again.

 

[Gooserider]

Yes, understood. I was refering to your local building code as a violation of that code will give your insurance company an instant out if there were to ever be a claim.

Like anything dealing with the gov't, a great deal depends on the official involved, but most code officials, insurance companies, etc. are going to be satisfied by manufacturer's manuals - many codes are even written to say X is required unless something else is specified by the manufacturer... As a specific example, look at the NFPA clearance requirements for woodstoves - very large numbers UNLESS the manufacturer has certified the stove to a lower number, in which case the manufacturer's number rules...

Gooserider

 

[Sawyer]

Yes, understood. I was refering to your local building code as a violation of that code will give your insurance company an instant out if there were to ever be a claim.

Like anything dealing with the gov't, a great deal depends on the official involved, but most code officials, insurance companies, etc. are going to be satisfied by manufacturer's manuals - many codes are even written to say X is required unless something else is specified by the manufacturer... As a specific example, look at the NFPA clearance requirements for woodstoves - very large numbers UNLESS the manufacturer has certified the stove to a lower number, in which case the manufacturer's number rules...

Gooserider

I was told by my agent that I was approved to install following Garn's installation manual. That is what I will do.