Rockwool around Fireplace insert

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eshwars

New Member
May 22, 2021
22
seattle
Hi all,

I just got a new Pacific Energy Summit Insert put in. After the installers were done, I took the surround off and thoroughly insulated all around the unit with Rockwool. They had already installed a Damper insulation plate, but I didn't like the idea of so much open space around the unit because it pulls outside air from what used to be the fireplace's ash cleanout. I was concerned that I would have drafts coming in from there.

I was careful not put anything that would block the intake or the fan air channels.

Once I had spent a couple of hours doing this and put the surround back in place, I was hit by a sudden fear because I realized I hadn't first checked on this forum if this was a good idea.

Is it ok insulate all the cavities around the insert with Rockwool? Thank you in advance for sharing your knowhow on this.
 

clancey

Minister of Fire
Feb 26, 2021
2,353
Colorado
I am far from a expert on this but I would think there is better material out there to insulate around your insert spaces to keep out the draft. I did find this article about Rockwool and wanted to share it with you.
 

BCC_Burner

Feeling the Heat
Sep 10, 2013
452
Uptown Marble, CO
What does the manufacturer say about clearances to the unit? That's your starting point. Also, rockwool is highly air-permeable, just like fiberglass batts, so it isn't going to do much of anything to stop drafts.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
28,684
central pa
I am far from a expert on this but I would think there is better material out there to insulate around your insert spaces to keep out the draft. I did find this article about Rockwool and wanted to share it with you.
Rockwool is the best product for this.

Hi all,

I just got a new Pacific Energy Summit Insert put in. After the installers were done, I took the surround off and thoroughly insulated all around the unit with Rockwool. They had already installed a Damper insulation plate, but I didn't like the idea of so much open space around the unit because it pulls outside air from what used to be the fireplace's ash cleanout. I was concerned that I would have drafts coming in from there.

I was careful not put anything that would block the intake or the fan air channels.

Once I had spent a couple of hours doing this and put the surround back in place, I was hit by a sudden fear because I realized I hadn't first checked on this forum if this was a good idea.

Is it ok insulate all the cavities around the insert with Rockwool? Thank you in advance for sharing your knowhow on this.
Most manufacturers want some space around the stove. I would check with PE.
 

Solarguy3500

Member
Dec 3, 2020
248
Western MA
One concern that I have seen mentioned in a few threads on this forum about this topic is the possibility of the blower fan sucking in some fine dust and fibers from the Rockwool and blowing it out into the room.

What I plan to do when I install my insert is first, use the foil faced roxul which should bind the fibers to some degree. Then I went a step further. Since I have a big fireplace with lots of room, I designed a series of metal heat shields that I will fabricate and install between the insert and the roxul on the back and sides of the fireplace, that way it should keep any dust from the roxul sealed behind the metal heat shields. I plan to seal all the joints in the metal with furnace cement. I may be overthinking this, but my wife has asthma and I want to make sure I don't cause any problems for her with the insulation around the insert.

I'll post pictures on my install thread that I started a while ago when I get to that point.
 

begreen

Mooderator
Staff member
Nov 18, 2005
93,764
South Puget Sound, WA
One concern that I have seen mentioned in a few threads on this forum about this topic is the possibility of the blower fan sucking in some fine dust and fibers from the Rockwool and blowing it out into the room.

What I plan to do when I install my insert is first, use the foil faced roxul which should bind the fibers to some degree. Then I went a step further. Since I have a big fireplace with lots of room, I designed a series of metal heat shields that I will fabricate and install between the insert and the roxul on the back and sides of the fireplace, that way it should keep any dust from the roxul sealed behind the metal heat shields. I plan to seal all the joints in the metal with furnace cement. I may be overthinking this, but my wife has asthma and I want to make sure I don't cause any problems for her with the insulation around the insert.

I'll post pictures on my install thread that I started a while ago when I get to that point.
Keep us posted. Furnace cement might flake off. You can seal the joints with black RTV. They will not get extremely hot.
 

clancey

Minister of Fire
Feb 26, 2021
2,353
Colorado
Sounds like your going to get that situation in control..Always nice to see a man treat his wife's conditions with concern--good for you and bless you...Knowing nothing about nothing--I am a old lady but I came across this on the web that I thought was interesting and good readable material and comparison of different things with a chart...clancey

 
Last edited:

eshwars

New Member
May 22, 2021
22
seattle
My apologies. I heard back from Pacific Energy but forgot to update the thread. Here's what they said:

1st response was that I could insulate behind the insert (back wall of fireplace). But when I asked a follow up question, I'm guessing the support person checked with the technical expert and changed the recommendation:

2nd response was that I should remove the insulation from around the insert, including behind it, or the insert will overheat! Dang! That' unfortunate. I'm going to have to disassemble the surround and undo all the work I did insulating. But instead or removing all the insulation, I'm instead going to put a 2 inch spacers (rolled up chicken wire) around all the walls. Hopefully that'll be the best of both worlds: allow adequate air circulation around the unit to keep it from overheating, while also reducing the air drafts coming from the ash cleanout (the problem I was trying to fix).

If anyone has thoughts for a better solution, please let me know. Thanks!
 

begreen

Mooderator
Staff member
Nov 18, 2005
93,764
South Puget Sound, WA
I'm ok with insulating behind it, but in our mild climate it may not be necessary to achieve good heating with the insert.
 

Geoff C

Burning Hunk
Oct 29, 2011
149
PA
I put rock wool to fill a large space behind my insert. Then I covered it with durock and sealed the seams with rtv. As long as you maintain the stove clearances I don’t see how they could say it will overheat. If you jam it in there I could see the concern.
 

jetsam

Minister of Fire
Dec 12, 2015
5,337
Long Island, NY
youtu.be
When Roxul (as it used to be called) first came out, they sent us a sales guy. He cut a square of roxul, stood it up in front of a butane torch (~2600°F), and let the torch stand on his little table, torching the Roxul, for about 8 hours. At the end of his day, there was maybe a 1" hole scooped out of the Roxul, but it got torched for a solid 6-7 hours (it had breaks to refill the torch, etc).

They are not kidding when they say it's fireproof. I think a cinder block would have suffered more damage than the Roxul did.
 
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mellow

Resident Stove Connoisseur
Jan 19, 2008
5,385
Salisbury, MD
It would be better to use a material that attaches to the walls so you create a chamber around the insert without touching it.

 

Solarguy3500

Member
Dec 3, 2020
248
Western MA
Definitely read through @mellow thread that he linked to. A lot of really good info in there and it was what inspired me to design my setup that I will be installing with my insert with roxul and metal heat shields. I might get some Micore to put under the insert too and possibly on the back and sides behind the heat shields if there's room.

Keeping the heat in the house and not letting it radiate out through the masonry and go up the chimney is probably the best thing you can do to get the most heat out of your insert.
 

NoGoodAtScreenNames

Feeling the Heat
Sep 16, 2015
447
Massachusetts
When I did mine I was thinking about the heat shields to keep the Roxul off the insert. Then I thought about it and realized that my stove already has a convective jacket which accomplished the same thing by creating about an inch of air space all around. I figured the extra Roxul was better than a second air gap. Not sure if that will apply for you but maybe something to think about.
 

Phileo

New Member
Dec 15, 2021
2
Massachusetts
It is the Roxul/mineral wool that is the culprit! I had a wood stove insert installed and Roxul was stuffed between the new uninsulated flue and the existing masonry flue. For a year everytime we lit the stove about 30 minutes into the burn a strong chemical odor would fill the room. We tried everything, and then eventually tried heating a piece of the Roxul on our kitchen stove--same smell. After we removed all of the Roxul, vacuumed, and wiped the Roxul dust off the stove the smell went away. I don't know what brand of mineral wool was used, but when in contact with very high heat it emits a smell. It might be fine if not directly in contact with an uninsulated flue, but I wouldn't use it and was shocked based on it being frequently marketed with a blowtorch trying to ignite it!