block off plate at top...fiberglass below???

[SeanG]

Hi all,

I am talking with my local stove company re: their install procedures and they said that on a new insert (Regency i2400 btw) they would install the block off plate at the top of the chimney and then put fiberglass insulation below the block off plate.

From everything I've read here it seems as though most of you have installed the block off plates at the bottom of the chimney near the damper.

Why would one install the block off plate at the top and stuff insulation down the chimney?

I have asked the same questions of my retailer and am waiting for a reply. I will post the reply when I get it.

Sean

 

[BrotherBart]

What they are calling a block off plate is the top plate for the liner install. Standard stuff. A block off plate goes at the bottom to keep that hard earned heat from rising and getting absorbed into the chimney instead of the living space.

 

[DAKSY]

Their "block off" at the top of the chimney is probably part of the cap anchor plate that is bent to the shape of the flue tile.
Insulation under that plate is a good a idea, & I did it on every liner install. They should also install a block off at the bottom that
is insulated as well. The theory is that the lower one will allow the insert to heat up quicker & begin radiating that heat back
into the room. Without the lower plate, the entire masonry assembly, including the chimney, has to heat up before you start
getting heat in the room. The insulation at the top & bottom will create a pocket of "dead" air between them, which will also
act as insulation in the chimney. Tell the installer you want one at the damper area as well as the top.

 

[SeanG]

Thanks guys. Here is what they said when I asked them about their instillation procedure:

"To answer your other questions:

Yes, we use a block off plate at the top of the chimney, which is included in the installation price. We don't use a plate at the bottom of the chimney, and just stuff the area with fiberglass insulation.

The liner is surrounded by a ceramic fiber insulation blanket. In most cases, that serves as sufficient insulation for the liner, and keeps the heat from escaping through the walls of the chimney."

I don't understand how they will keep the insulation from falling into the fireplace if there is no block off plate at the bottom.

Is fiberglass insulation a poor choice? Why wouldn't they use Roxul?

Thanks.

Sean

 

[DAKSY]

I have used unfaced fibeglass in the damper area without any issues, much to the chagrin of many members here.
If enough of it is crammed up in there, it won't fall out, & it works very well.

 

[bholler]

Do not use fiberglass it can melt i have seen it. Like everyone else said they are referring to the top plate. But i would insist on an insulted liner and a block off plate on the bottom. That is how it should be done and if they wont do it find someone who will

 

[SeanG]

Do not use fiberglass it can melt i have seen it. Like everyone else said they are referring to the top plate. But i would insist on an insulted liner and a block off plate on the bottom. That is how it should be done and if they wont do it find someone who will

Thanks BHoller. I will call them to verify if they will do it or not.

 

[bholler]

And make sure they use the proper insulation for the liner not just shove fiberglass down the top and up from the bottom that is not the right way to do it.

 

[DAKSY]

Not gonna argue with you, bholler, but I've never seen it melt & I installed & serviced for 11+ years.
When I pulled my Regency 3100L after 5 years of burning, the pink insulation had turned a yellowish
color, but it had not melted, & the only area that had turned was in direct contact with the SS Liner.
The owner I worked for has been in the business since 1979 & in fact, wrote most of the NFI Wood
Burning Certification course final exam questions. He directed that we use the unfaced fiberglass.
His business & his reputation were on the line with every install his crews did.
I will take his knowledge & expertise over the combined knowledge here,
but different strokes for different folks.

 

[bholler]

wrote most of the NFI Wood
Burning Certification course final exam questions.

I am sorry but there is no where in the nfi or csia certificaion tests or literature that sayd fiberglass is ok anywhere in a chimney system. You might get away with it but why when you can buy ceramic wool that is tested and approved for the application. Or roxul that is at least rated for the proper temps. And the owner i work for (my father) has been in business since 1977 and has never and will never use fiberglass in a chimney

 

[DAKSY]

Like I said "different strokes"...I'm done with this one..

 

[bholler]

Like I said "different strokes"...I'm done with this one..

I agree that there are many different ways to do things. For example i think every liner should be insulated fully regardless of whether it meets code with out the insulation or not and i will agree that i am going above and beyond what is actually required there. But there is no way that stuffing around a liner with fiberglass meets any code or manufacturers directions. And therefore i think it is irresponsible to tell anyone it is ok to do so.

 

[Hogwildz]

Why not spend a few bucks more and just use Roxul?
A block off plate, sealed, will def stop air flow.

 

[SeanG]

Hi guys,
I spoke to another installer today and here is their SOP for insert installs:


- the insulated liner is dropped from the top of your chimney, fed through your notched damper and onto the stove.
- the 18 X 18 top plate is sealed to the top of your chimney (which prevents any air from entering the existing chimney). This plate holds the liner and the cap is placed on top of it.
- where the liner goes through your damper, we use the same insulation as on the liner and fill the space to prevent any cold air (that may permeate through your brick, block, mortar) from coming around the unit.
- basically, once the liner is installed..............your chimney becomes a void/ dead space as all air movement is between the stove and liner.

They too don't seem to be installing a block off plate at the bottom. Is this industry standard now? It sounds like they are achieving the same end result, minimizing heat loss up the flue/chimney but they are choosing to use a different method rather than use a block off plate at the bottom.

Thoughts?

Sean

 

[begreen]

A block-off plate is always extra. It takes more skill and labor to do this. That list is a pretty average way of installing particularly on a bid competitive job. The downside is there are details that get overlooked or passed by such as creating a drip edge by folding over the top cap sides, using Roxul instead of fiberglass, and installing a damper-sealing block-off plate. If this is an interior chimney installation then the lack of the block-off plate is not that big a deal. If it is an exterior chimney, then installing a lower block-off plate may help the insert retain more heat. The metal plate will do a better job at preventing stove heat from going up the chimney than stuffing the area with a breathable material. Some folks that also have room behind the insert have insulated the rear wall of the fireplace in order to retain more warmth around the insert. This would likely be a DIY project.

 

[SeanG]

Thanks begreen. How much should I budget for a block off plate.? Or rather, how much is too much?

By all accounts I should be able to let them do their normal install and see how things go then add a block off if necessary right? This is an exterior chimney.

 

[begreen]

It would be best to ask them for a quote. I'd estimate it will take them an extra hour (shop time included) at their going rate. If you opt for it, insulating the back of the fireplace (if there's room) is a DIY job that should be completed before they start the install. Just be sure there's room behind the insert to accommodate the insulation.