Block Off Plate vs. Rock Wool or Fiberglass Insulation

[daveespo]

I just had my Jotul C350 insert installed a few weeks ago and I wish I had read a few more threads about maximizing heat output. It seems like every thread mentions the block-off plate. Due to the fact that I didn't install it myself, I didn't have the opportunity to put in the block off plate when it was being installed.

Now, I'd like to know what my options are ... The outlet from the insert goes into one of those adjustable galvanized 6" elbows (the kind where you rotate the sections to make the desired angle). It's mostly a straight shot upwards but it's angled slightly to get around the protrusions from where the old damper handle connected. The damper opening is a conventional 6" x 18" rectangle.

Can I just pack either Rock Wool or Fiberglass around the piece of stove pipe where it passes through the old damper in order to provide an air seal? Or is that a fire hazard?

I dread taking the insert back out in order to make the block off plate and fit it in there properly ...

Thanks in advance,
Dave

 

[Shane]

Alot of municipalities accept the insulation method. The general concensus most of us have come to is that the sheetmetal plate is the optimum solution in both durability and function. The insulation can begin to sag when exposed to condensation in the chimney.

 

[webbie]

Rock wool will not be a fire hazard. Fiberglass is not suggested because the part right next to the pipe may melt...but it still is not likely to catch on fire.

A good seal with the plates on the front on an insert like yours is probably OK as per the manual, etc. - A plate is much more important when installing something like a hearth stove or else when the front of the fireplace is very rough and a good seal is difficult.

 

[daveespo]

Thank you for the replies!

I fall into the group that has a really rough fireplace surround (gaps between the insert trim and the fireplace vary from 0-1") so I can't get a good air seal around the front of the unit without it being too obvious for my liking

When I have the trim kit off to install the insulation, I may try to make a modified block-off plate to support the insulation from sagging but I expect that the real air sealing will be from packing the insulation tight rather than being able to make a really tight fitting block-off plate

-Dave

 

[begreen]

Did the installer really use a galvanized elbow?

 

[daveespo]

I can't say for sure that it was galvanized vs. stainless ... I didn't see him bring it into the house and once he was inside the fireplace twisting it around, I couldn't say for sure.

I assume that galvanized is bad news for corrosion reasons? Is there some simple way to identify galvanized vs. stainless separate from the appearance of the surface of the metal?

 

[BrotherBart]

I can't say for sure that it was galvanized vs. stainless ... I didn't see him bring it into the house and once he was inside the fireplace twisting it around, I couldn't say for sure.

I assume that galvanized is bad news for corrosion reasons? Is there some simple way to identify galvanized vs. stainless separate from the appearance of the surface of the metal?

A magnet will not stick to the 304 and 316 stainless commonly used for chimney liners, pipes and connectors.

 

[swestall]

Personally, I'd have them back out and have them do the job right. You are losing heat and I think the code requires a block off plate. Its safer and you should sleep better with it in.
As always, Craig has the info (on insulation fiberglass is not good as it sucks up water as well as potentially melting).

 

[crazy_dan]

I can't say for sure that it was galvanized vs. stainless ... I didn't see him bring it into the house and once he was inside the fireplace twisting it around, I couldn't say for sure.

I assume that galvanized is bad news for corrosion reasons? Is there some simple way to identify galvanized vs. stainless separate from the appearance of the surface of the metal?

Not so much for corrosion but it gives off very bad gases when heated and can make you and your family sick.