Insulation around fireplace?

[Boris]

Recently installed a VC Merrimack insert (external wall fireplace / chimney).
Everything is fine but I did notice that the outside of the fireplace structure gets warm, so I'm losing some heat to the outdoors. Block off plate + insulation is already installed.
Any thoughts on insulating around the insert?
I have about 5-6" all around the insert and have been thinking:
1) Stainless steel sheet around the fireplace with rockwool insulation behind it. SS sheet to reflect IR.
2) Put solid bricks all around the fireplace with rockwool behind them. Bricks will provide some insulation and increase the thermal mass. Heat up when burning, release heat when the fire dies down.
3) Some combination of the above?

 

[begreen]

All you need is the rockwool, but if you want to dress it up, Durock cement board works well or you can use Micore or they make a Roxul in board form. I

Is there a block-off plate in the damper area? If not, that can make a nice difference too.

 

[bholler]

Or galvanized sheet no need to pay for stainless

 

[therealdbeau]

Do you have an insulated liner going all the way up the chimney? The reason I ask is I'm under the impression that having a liner run the full length of the chimney negates the need for block off plate.

I also have the Merrimack insert also mounted on an external wall chimney. It takes a while to heat up and I'm wondering if insulating around the unit will help with this.

 

[Boris]

I do have insulation around the liner (but only 1/4"). I put in the block off plate to stop cold air from around the liner, between liner and original chimney.
I just added the following setup:
Original fireplace walls -> Rockwool insulation -> Thin Sheetmetal-> Layer of solid bricks -> Merrimack Insert.

The idea is that bricks will absorb the heat and work as a big thermal mass, smoothing out the heat up and cool down. Basically more heat after the fire goes out. The sheetmetal and the rockwool are to limit heat escaping to the outside walls.
Going to test this out in the next couple of days.

 

[therealdbeau]

Sounds a little overkill but I like it. Let me know how it goes. I might try lining the fireplace with just Rockwool if it'll help the insert heat up faster/maintain heat better.

 

[bholler]

Do you have an insulated liner going all the way up the chimney? The reason I ask is I'm under the impression that having a liner run the full length of the chimney negates the need for block off plate.

I also have the Merrimack insert also mounted on an external wall chimney. It takes a while to heat up and I'm wondering if insulating around the unit will help with this.

It negates the code requirement yes. But a blockoff plate will still greatly improve performance even with a full liner

 

[therealdbeau]

It negates the code requirement yes. But a blockoff plate will still greatly improve performance even with a full liner

Hmm.. I'll have to look into this. Would stuffing the flue opening with ceramic wool blanket achieve the same thing? I think fabricating a plate to cover the hole is outside of my capabilities.

 

[bholler]

Hmm.. I'll have to look into this. Would stuffing the flue opening with ceramic wool blanket achieve the same thing? I think fabricating a plate to cover the hole is outside of my capabilities.

Stuffing insulation in will help yes but some air can still flow through it.

 

[therealdbeau]

Stuffing insulation in will help yes but some air can still flow through it.

Okay thank you. Also, what exactly are we defining as "performance" here? More heat from the unit, better draft from the exhaust, all of the above and more? Just trying to see what I stand to gain by the extra work. Thanks

 

[bholler]

Okay thank you. Also, what exactly are we defining as "performance" here? More heat from the unit, better draft from the exhaust, all of the above and more? Just trying to see what I stand to gain by the extra work. Thanks

More heat in your house and less going outside

 

[mellow]

Okay thank you. Also, what exactly are we defining as "performance" here? More heat from the unit, better draft from the exhaust, all of the above and more? Just trying to see what I stand to gain by the extra work. Thanks

Finally got around to insulating my fireplace

 

[therealdbeau]

@Boris, Did you notice any significant difference with all the insulation vs. no insulation? Does the fan come on quicker? Ultimately, was it worth the effort?