Insert Insulation - noticeable improvements?

[SculptureOfSound]

I'm curious what kind of results you've had if you've put insulation around your insert. I would think the back and top would make the most difference but has anyone noticed significant heat output or burn time changes from insulating the sides?

I've got an exterior masonry fireplace and am trying to figure out if I'd be better off going with an insert with a bit smaller dimensions which would allow me to insulate around the sides (will have room to insulate the back/top no matter which choice), or just going with the biggest insert I can fit into the space.

So, where did you insulate (and how much) your insert, and what kind of changes have you noticed?

Thanks guys! I'm trying to decide before the end of the month and your input really helps!

 

[cableman]

Id go the biggest insert that fits, chances are you can still insulate back and if not just use some durarock or better yet micore board if you can find it.
I was able to insulate back with roxel and cover with durarock, but only the back of my chimney is exterior. Not sure if it made a big differance cause i never had it any other way.

 

[kennyp2339]

A block off plate with insulated liner is way more important than insulating the fire box, I'd go with the largest insert you can fit and just make sure the block off plate and liner is installed. FYI when you in the 2.5 cu ft range in fire box size you will generally have burn times in the 7 - 10hr mark for an epa air tube reburn stove.
Wishing you the best of luck, also keep up with pic's on the install process when you decide to pull the trigger.

 

[Lloyd the redneck]

I stuffed as much insulation as I could around my insert top back and sides. Don't know if it makes a difference or not but seems like it must

 

[redktmrider]

I installed a block off plate and insulated around my insert with Roxul, the electric heat now kicks on at 10f outside temp vs 20f before the added insulation and plate. The exterior chimney is on a north facing wall of a two story house.

 

[begreen]

I installed a block off plate and insulated around my insert with Roxul, the electric heat now kicks on at 10f outside temp vs 20f before the added insulation and plate. The exterior chimney is on a north facing wall of a two story house.

Yes, a blockoff plate and rear insulation can make a significant difference with an exterior wall fireplace.

 

[SculptureOfSound]

I installed a block off plate and insulated around my insert with Roxul, the electric heat now kicks on at 10f outside temp vs 20f before the added insulation and plate. The exterior chimney is on a north facing wall of a two story house.

Wow, that is a huge difference.

What depth of Roxul did you use?

Also, did you do the blockoff and insulation at the same time? I presume the blockoff probably added the most benefit but am trying to figure out how much improvement insulation will add. I think it might be hard to find people who have done the two procedures at different times, though

 

[SculptureOfSound]

Would there be a problem with the roxul directly touching the sides of the insert?

The inserts I'm looking at will only give me maybe 2 inches on the sides, so I'd have to have some compressed roxul in there - touching the side of the insert - if that would be safe.

 

[bholler]

Would there be a problem with the roxul directly touching the sides of the insert?

The inserts I'm looking at will only give me maybe 2 inches on the sides, so I'd have to have some compressed roxul in there - touching the side of the insert - if that would be safe.

Ask the stove manufacturers they are the only ones that can tell you

 

[SculptureOfSound]

Ask the stove manufacturers they are the only ones that can tell you

Thanks, I will ask them asap, as this will likely be a factor in what I decide to go with.

 

[kennyp2339]

Would there be a problem with the roxul directly touching the sides of the insert?

The inserts I'm looking at will only give me maybe 2 inches on the sides, so I'd have to have some compressed roxul in there - touching the side of the insert - if that would be safe.

My take is that roxal has a million fibers that are packed tightly together, I personally would want roxal installed with it covered either by sheet metal or cement board, I wouldn't want the fiber dust to be blown into my room from the insert blower.

 

[begreen]

If clearances are tight I would use micore board cut to fit.

 

[mellow]

At a minimum use cement board if you are tight on space and install a block off, you will see a difference.

 

[SculptureOfSound]

Mellow, you seem to have a lot of firsthand experience on a before and after, so I'd love to hear your thoughts (anyone else feel free to chime in, too!)

If you were deciding between the below two inserts, which do you think would give you more heat/longer burns?

Note, my chimney is almost completely exterior, the inner face of brick does not extend *at all* into the room (flush with adjacent walls which are built-in bookcases)

Insert A
2.35 ft box
about 1.5" on each side for durock/roxul
about 2 inches in back for durock/roxul
about 3 inches above (not including damper space)

Insert B
2.1 ft box
about 4 inches per side for durock + roxul
bout 4 inches behind for durock + roxul
about 5 inches above (not including damper space)

Obviously a 2.35ft box will give me more wood to burn, but then I could get about double the insulation on option B - so I'm thinking that could more than make up the difference. Efficiency #s and the like are almost identical on the two inserts, so the only difference (on paper at least) is firebox size and amount of space for insulation.

Thanks
-Seth

 

[cableman]

I would go the biggest insert that i liked, roxel durarock on back wall, durarock on sides, silicone all seams, blockoff plate with as much insulation above as possible.

Heres how i just installed my neighbors....
https://www.hearth.com/talk/threads/drolet-1800i-install.162974/

 

[yooper08]

First question I would ask is, what's the space I'm expecting to heat with the insert? Yes, you'll reclaim what would be lost heat by insulating the fireplace, however, the size of the space needing to be heated and matching that up with the insert is more important in my mind . The other consideration is how well that space is insulated/air sealed? The marginal heat gained from insulating relative to the output of the insert may not mean a whole lot depending on those answers.

Compressing Roxul reduces it's R value as with any insulation. So, looking at the entire system in a vacuum and not considering the above, the smaller insert would be better when looking at reclaiming what would be lost heat. But if the insert is undersized for the space, the only way to fix that is getting a larger insert.

 

[SculptureOfSound]

Yooper, we're looking at 1650 sq ft of total space upstairs on our ranch, with only 1050 of that being the "communal" space, and then the rest being a narrow hall that.leafs to the bathroom and bedrooms.

The fireplace itself is on the far end of the house in a 20*13 family room that is quite open (6 foot opening) to the dining and kitchen area. Then there is a living room on the front side of the house.

One thing to note is the family room was an addition behind the garage so it effectively has 3 external walls. That's why I'm thinking insulating the totally exterior masonry fireplace as well as better insulation in that room will help preserve the heat generated, and had me thinking that picking an insert that allows me to optimize for insulation is priority #1, at least when the stats are as close as they are with the two options I listed above (the Voyageur grand and Montpelier, respectively)

 

[SculptureOfSound]

Some thoughts relevant to this thread...


Girlfriend and I drove about 50 miles today to check out the Montpelier. Really nice looking unit although it felt a bit cheap. The door did not feel substantial like on say, the Voyageur Grand, and the door hinges we're definitely weak. Where you could sit on the door of the Voyageur grand and I don't think it would budge, it feels like the Montpelier's would snap if you attempted the same. The door handle seemed a bit flimsy too. The rest of the unit seemed nice - really liked the look of the firebrick panels (can't think of the proper term) in the Montpelier - looks a lot nicer than standard firebrick.

If I had more clearance in my firebox my choice would be a no brainier - the Voyageur grand. I think it looks nicer and is built better....and has a bit bigger firebox. But, only with the Montpelier could I heavily insulate my totally external masonry fireplace. the bricks were so cold last year that I think heavy insulation would pay more heat dividends than a slightly bigger firebox...not to mention the Montpelier has the option for a 3" extended mount which I would go with to meet mantle clearances. That should mean more heat, too.

 

[redktmrider]

Wow, that is a huge difference.

What depth of Roxul did you use?

Also, did you do the blockoff and insulation at the same time? I presume the blockoff probably added the most benefit but am trying to figure out how much improvement insulation will add. I think it might be hard to find people who have done the two procedures at different times, though

I used 1 batt thickness and cut it to length, my fireplace is rather large. I installed the block off plate and the same time as the Roxul.

 

[mellow]

Make sure you are comparing USEABLE space in the insert, some manufacturers love to include space above the baffle in calculations.

If you are wanting longer burns then go with the largest cat insert you can fit. Either that or look at rear exhaust stoves and put it in front of the fireplace if you have the room.