Alurra Fiber Cement Board acceptable for insulated surround for insert

[Tracks74]

I have been toying with the idea of building an insulated surround and block of plate for my insert to increase heat output to the house (versus heating the large fireplace chimney).
I have done quite a bit of reading about the topic and have seen where people have used durarock or Micore for casement boards with Roxul wool insulation between the boards and the fireplace walls.
My local store does not have Micore and they recommended I use Alurra Fiber Cement Board. I want to make sure that would be ok in lieu of Durarock or Micore.

Allura™ 1/4 x 3' x 5' Fiber Cement Underlayment

This Fiber Cement underlayment is installed over the subfloor to provide a smooth, water-resistant, durable surface in which porcelain or ceramic tile may be installed. It may also be installed for countertops in conjunction with tile. These products feature a dense, non-porous surface making...

www.menards.com

That is a link to the product at my local Menards that I was looking to use.

Thoughts?

 

[begreen]

Cement board and this fiberboard are very different from micore, which is a thicker and more porous insulation board. I am leary of using the Alurra. It has wood fibers in it. Normally, sheet metal is used for a block-off plate.

Can you post a picture of the current installation so that we can see what you are starting with?

 

[Tracks74]

Well, I probably messed up a bit. I have a VC Montpelier and I live in a 1966 Ranch (single story) home. We try hard to get this unit to heat the whole house without supplementing with our furnace, but we never can do it.
The insert is located in a rather spacious fireplace. The fireplace is full brick from the first floor and about 3 foot above the peak line of the roof. The chimney is located against the unheated 2 car garage. During the winter, the garage stays at about 35 degrees on the coldest days here in WI because the insert is keeping the fireplace very warm; much of that heat I would rather see in the house.

I have read about constructing an insulated box and block off plate for a while and decided to try and get it done while I was on vacation last week. My local store, Menards did not carry durarock and offered up the Alurra cement board as their alternative now.
I was hoping to get buy without having to drill holes into the fireplace masonry on the inside (for ease if nothing else), which is why I avoided using sheet metal for the top side.

I constructed a 25" high box using the Alurra board and insulated behind it with Roxul steel wool insulation (melting temp of 2150 degrees). I built the top to be large in dimension than the sides, which then keep the top propped up.

I already put the insert back in, but maybe I will need to pull it out and put sheet metal up. I appreciate the feedback.

 

[begreen]

The pictures help a lot. There still is a good airgap around the insert. I just went and looks at the safety data sheet for Alurra and it's listed as non-combustible. Seems similar to Hardibacker, 4.5-9.5% cellulose in a cement and quartz dust base. It's probably ok. The hottest area is where the liner passes thru.

This should make a nice difference this year for increasing the heat output that stays in the room. The garage may be a bit cooler though.
PS: Roxul is mineral wool insulation.

 

[Mech e]

Better than insulation would be to get some air movement. Find an air mover that can live under the stove and blow air into the fireplace.

 

[begreen]

Better than insulation would be to get some air movement. Find an air mover that can live under the stove and blow air into the fireplace.

It's an insert with its own convective jacket, minus the surround.

 

[Mech e]

It's an insert with its own convective jacket, minus the surround.

Right you are. Couldn't tell from my phone and old eyes.

 

[Tracks74]

The pictures help a lot. There still is a good airgap around the insert. I just went and looks at the safety data sheet for Alurra and it's listed as non-combustible. Seems similar to Hardibacker, 4.5-9.5% cellulose in a cement and quartz dust base. It's probably ok. The hottest area is where the liner passes thru.

This should make a nice difference this year for increasing the heat output that stays in the room. The garage may be a bit cooler though.
PS: Roxul is mineral wool insulation.

So the short answer is I should be OK right?

 

[begreen]

So the short answer is I should be OK right?

Yes, as long as the product is non-combustible it should be ok. Keep us posted on how it performs now. I'm not a fan of cellulose cement products around hot flues, but the mfg. says it is non-combustible.