Hello all, halfway done with PE insert install w/ pics & Question: Insulating fireplace?

[Beau]

Hello all, I'm pretty much brand new here, but I've done quite a bit of reading and enjoy the challenge and rewards associated with dialing in effiency with any system.

So a licensed professional and I are installing my Pacific Energy Super insert.
We've knocked out some bricks due to an unevenness with my my hearth, and we've mortared in a flat slab for most of the insert to rest on. Messy here at the moment due to lots of soot cleaning, and wet mortar. :]

And we've very nicely wrapped up my double walled 6" machine ovaled (for clearance) liner. 1/2 inch liner... We sprayed adhesive to get the insulation to stick (with adhesive for this purpose), wapped it, cross taped the seems. Caged it, clamped the cage and spiral bound the wire mesh (cage) with stainless steel wire.

We were able to stuff it up the chimney after knocking out some interior bricks, and cutting out the old flue door frame.

So I'm excited so far, just a bit more work to go.
We are going to be using the same insulation to insulate a block off plate here.

So here is my question.
In this poorly taken photo below, can I insulate the interior of this fireplace?

I ask because from what I know about thermal transfer (I work with the the principals all of the time for automotive turbo and performance applications)...

The fireplace is under grade, the surrounding brick embedded in the ground woul have a near limitless thermal sync. Even though the brick would be heated through convection and radiation primarily which as we all know isn't nearly as effective as direct transfer would still be an limitless sync to draw heat from around the stove into the ceramic of the chimney and ultimately into the ground.

So can I physically line this with Roxul, under the stove, the walls as well as the block-off? I know Roxul is rated high for heat, but can it easily withstand DIRECT heat transfer from the stove?

Mind you the back and sides of the Pacific Energy Super insert has a mostly sealed convection steel jacket around it, so it would not be touching the physical firebox itself, I believe this goes for the bottom as well.

Is that something I'm allowed to do?

What are some other ways to insulate this fireplace? Also is there anything that the stove could physically sit on? I think Roxul is quite thick, correct? I'd need something compressible if possible.

Thanks guys!

 

[Eaglecraft]

Beau:

You've got an interesting project going. Yes, there should be no issues with using ROXUL insulation behind the stove. As you suggest, I wouldn't put the ROXUL in direct contact with the stove. You might consider fabricating (or having your steel fabricator) a cage having three sides using 1/8 inch steel welded together. The ROXUL, typically 2 inches, can be placed behind the steel. The steel will hold the ROXUL in place and keep it from being in direct contact with the stove. Allow a few inches of air space between the insert and the steel plate. There should be air circulation to keep the stove from overheating.

Underneath the stove, you can slide a 2 inch piece of ROXUL to lessen heat loss to the concrete hearth. You can't have the weight of the stove on the ROXUL, but you can cut the ROXUL with a utility knife to fit around the leveling legs of the insert. You should allow space underneath the stove to for air circulation. If there is sufficient space, you could fabricate a rectangular box of 1/4 steel that the insert would sit on, then slide the ROXUL into the steel box. A welded 1/4 steel box should be able to support the weight of the stove.

Good luck with your installation. Looks like you've done a nice job. See this ROXUL product: http://www.roxul.com/building+envelope/products/roxul+rockboard®

 

[Retreadsme]

Beau,
I use 1" ceramic blanket behind the insert (sides & back) and on top of a metal block-off plate to keep heat from transferring to the outside wall bricks / heat sink. I personally would not worry about underneath the insert because there actually is a minor amount of heat radiating off the bottom of the insert. I have not used Roxul so will hold comment about it. Great pics & I know you're having fun.

 

[Beau]

Eaglecraft, thank you for the suggestion. Yes those are ideal scenarios, however due to the dimensions the edges of the stove will just almost touching the angled blocks towards the back, so not only do I not have space for a non-compressible insulation or realestate for the airspace b/t the steel and Roxul, but I probably would have just about 1/8th of an inch worth of clearance itself.
Think of that slab of rock as the outter dimension of the stock itself basically.

I was wondering if there was something more along the lines of what Retread was talking about. The ceramic blanket sounds like it would be compressible for where the edges of the stove would nearly come in contact with the brick.
Another reason for this is the amount of moisture this mortar and brick sees, I'd like to keep moisture away from the insert as well, so I was really looking to line it pretty well.

I had other thoughts, such as using heat radiant reflective backing, or some sort of ceramic coating paint.

Do you guys have any other thoughts about that?

 

[madison]

I had other thoughts, such as using heat radiant reflective backing, or some sort of ceramic coating paint.

Midnight, after many drinks. My thought as well, could not hurt to add a radiant reflector behind or in front of the roxul. Gonna crash any moment

 

[Beau]

Is Roxul a rigid, or a compressible media, similar to fiberglass insulation?

 

[Beau]

And knowing what I know about thermal transfer, paint won't slow any heat transfer, so I guess I'd have no way to actually bake on a true thermal ceramic coating. So I guess I'd be stuck with the heat radiant backing, but I'd prefer something like a ceamic wool or something to that extent.

 

[Hogwildz]

You'll be fine insulating, and yes, the PE's have a casing around and on are up off the floor so to speak underneath. If your not hooking an OAK to it, you may want to leave some sort of path where the inside air knock out is on the side casing. to the grille on that side. The one thing you may want to consider is if the Roxul fibers will be blowing all over from the blower unit. May want to put some sort of rigid barrier covering the Roxul to keep dust and fibers from it from blowing into the house and breathing that stuff in.

 

[Beau]

Hey HW, thanks man I appreciate the response. I won't be hooking up an OAK to the insert, but I wasn't following exactly the couple of sentences after that.

I'm visualizing the insert, and from what I can remember they try and seal that up as best as possible, but there are some gaps.

Were you just saying to try and find a way to prevent the gaps in that convective air chamber from blowing air in the fireplace through the gaps in my surround - thus blowing Roxul fiber into the living space?

If so, that's something to think about for sure. Do you have any ideas on how to mitigate that? I could try and put a reflective tape on the Roxul. The good news about Roxul is that I've found the fibers will actually break down unlike organic fibers. For instance even cotton may never break down if the fiber bits are larger than the cell can consume, where as the fibers from Roxul can. My guess is that it's because they are made from iron reduction and rock mineral. Which sound like something we couldn't break down but in reality comprise us quite a bit.

So HW in your opinion it would be ok to use some soft Roxul and mash the insert against it, especially since it has an air chamber that runs through it?

Also guys one of the reasons I really liked the PE is that it's designed to move air through convective movement. It specifically states in the manual that even if the blower isn't working due to power outage that the design still allows for adequate air movement.

 

[Stax]

Kaowool. Rigid non-flammable insulation board perfect for your needs. Available at any local HVAC supply house. I have 1.5" that sits atop my block-off plate.

 

[madison]

Hog was referring to the blower which circulates air around the exterior of the insert. And the fact that the exterior shell will have some gaps etc, where the blower air will escape the envelope and start moving the roxul around.

The blower increases BTU output into the room. Depending on the room, home location, climate, outside temp and wind etc, you may or may not need the blower. Note that it is not an option with the insert - that may be a clue.

If you said you lived in a leaky cabin in Alaska - the natural convection will not cut it.

You can add that to your signature and ID....

 

[Hogwildz]

More like what Madison explained. Plus, PE inserts, have a 4" knock out hole on the side of the outer casing. This is were the insert supposedly takes its air from. The knock it is punched out, and instead of taking outside air, it takes inside air from the front side grille to the knock out hole in the side of the "gray" outer casing. On the Summit it is on the left side when your standing in front of the insert looking at the face. On other units it may be on the other side, but it is always on the side casing. This is where you will want to leave a path from the knock out in the casing, to the front grille on whichever side the knock out hole is on.
Make sense?

 

[Beau]

Yeah, I'm visualizing now. So it's only a 4 inch square opening eh? I see there are other areas for air inlet (air wash system for the glas just underneath etc) but I'm surprised that the 4 inch opening is the chief sources for the convection system and blower.

I guess I'd be looking at another point, and really my main concern, over heating the stove.
Now I'd imagine 3/4s of an insert wouldn't have to be in a 55 degree fireplace chamber in order to survive, since free standing woodstoves are in 70ish degree heat on all sides...

I figured that if I could keep it warm on all sides of the stove that I would just be able to throttle the insert back a bit more, saving wood and heat.
But the one thing I cannot calculate is the temperature requirements of the stove.

If I kept the temp below 700 I should be ok, right?

 

[begreen]

I would skip trying to insulate the fireplace cavity if you are worried about overheating the insert. An insulated blockoff plate should suffice.

 

[Beau]

Well, actually I think you guys will need to tell me if I should be worried or not. I mean I'd assume I'd just throttle the fireplace anyways, yes?
The insert is also thermostatically blower controlled.

So what do you think? I'd rather not lose the 5-10??? maybe 15% of wood BTU through cold, partially damp, morter and block thats buried in the ground, I'm also looking to do this to keep moisture away from the insert when not in use.

You guys have the experience though :]

 

[begreen]

If you are concerned about rusting, damp insulation is going to be worse IMO. It will retain moisture. That could also create a mold problem. In this case I would remove the surround, at least in the off season and definitely wouldn't insulated the fireplace box. But if you insist on insulating consider using kaowool board instead.

 

[Beau]

Roxul is moisture resistant, and impervious to mold.
That's a good idea to remove the surround during the summer perhaps! Too bad it'll add to the nasty musty smell downstairs. LOL

 

[begreen]

True it's moisture resistant, but how much moisture will it hold?

 

[Beau]

It won't hold moisture like a traditional insulation. According to the manufacturer. It's designed for moist/wet environments. The material is hydrophobic so it won't continue to wick into the materical using capilary action like an absorbant material.
In otherwords only the outside would be exposed to the moisture, and not the volume of the product.

 

[Hogwildz]

I know it sucks if you have to pull it back out, but why not try it without the Roxul and see how it works?
You may find it does fine without and need not worry about it. If you feel you still need it, slide the insert out and pack away with the Roxul.
The air intake punch out on the Summit is a 4" round knock out. Not sure bout your model, but prolly along the same lines. Don't know about it being square though.

 

[BrotherBart]

If removing the surround on the Summit doesn't require pulling the insert out he could just take off the surround and pack it. I can't see why worrying about the Roxul being against the shroud would be a problem. That insert would be a molten puddle before the Roxul even started getting soft.

 

[Beau]

Yeah, I think that's what I'm going to do. I'll put a tiny bit of batting to fill some voids (very very small amount) just beacuse I don't want to back fill it with motar or concrete just yet. And If I need to insulate around it I will if not then I'll already be done. Problem is I won't really know if I need it unless I try putting it in.

Thanks for the advice guys.
I'm sure there will be a thread pretty soon with either failing at fire building, or perhaps some success!

 

[Beau]

Ok guys, 80% done with the install. Just need to square away some stuff. But, I have some pictures about what I decided to go with for the fireplace!
First of all, thank you guys for all of your help. Between your advice and speaking with lead on the project I've decided to completely insulate the fireplace.

I went to Home Depot locally to me, and of course they were out of Roxul, just like they are out of the Trim they've been promising me for my front entryway for literally 3 months, every 2 weeks saying 2 more weeks it'll be in...
So I walked away without the insulation, and btw they had no idea what I was talking about (Roxul).

So when the Chimney guy came today, he said he was already going to use the same flu liner wrap for the block-off plate. He had a bunch of extra scraps sooo.....

Chimney guy working on the block-off plate.

Close up: You can see the masonary screws and washer we used to secure the insulation

After we scabbed up some more pieces - close up of the fastening system.

Here is a shot of the sides done.

And some piece I cut out for the bottom, I just laid them in there.

I think it looks awesome! Now for the insert going in and connected using a 15° elbow. It's not a smooth interior unfortunately, but the installer said it would have a very negligable effect, knowing what I know about fluid dynamics, it bothered me, but I'm sure I won't notice any difference in actual useage anyways so. But here is a nice little dramatic shot!

Connecting the liner. Some bend to it, but still a nice long radius!

The installer used few Rivets, good professional install.

And finally, but not finished. You can see a 3/4 inch gap b/t the finish panel and the fireplace front. Annnooiyyingg. So I'm going to have a 1 inch piece of sheet metal border around the fascade to finish it off nicely. I also need to extend the hearth in front a minimum of 5 inches, so I'm going to go 12 inches worth of Wood panel looking tile in front, I just got done cutting those up. Hopefully I'll be able to lay that thinset down tonight once I figure out how I want to totally finish off the tile.

I hope you guys enjoyed this update! Any question are welcome!

 

[jatoxico]

Hey lookin' good! Bet you can't wait to do that first burn in . From the look of the brick above the lintel you weren't getting good draft as an open fireplace. That new (insulated) liner should be a night and day difference.

 

[Beau]

^ yeah, I think you're right. I've never used it before but the previous owner did, he used terrible wood, and the fireplace opening was abormally high, so that could have also been a contributing factor.

I'll wash that brick down later when we go to actually clean up after all of the projects etc. You're right, I cannot wait at all. I don't think I'm allowed to burn in it before my inspection, so it's a REAL TEASE! I'm very happy though it's quite warm, in the low 40's, if it were cold I wouldn't be able to resist quite frankly :D