looking for installation advice on Jotul F 3

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alarminglee

New Member
Dec 22, 2023
2
Southern New Hampshire
New here, so bear with me...and I thank anyone in advance who has the patience and temerity to read through and respond to my grueling list of questions.

I'm looking for advice before installing a new (to me) Jotul F3, rear vent into an existing fireplace opening (or possibly top vent, up higher in the masonry chimney).

I've found at least 3 different manuals for apparently the same stove model, all differing in installation advice/clearances/efficiency/etc. Or maybe I just think it's the same stove model? The numbers and letters are baffling to me, even after reviewing Jotul's identification graphics. (The plaque on the back of my stove simply identifies it as an F3, but it has a curved door handle, so it looks to me like an F3 CB as shown in the identification graphic.)

Couple/few questions:

1. Can someone clear up for me whether the F 3 and the F 3 CB are in fact the same model? When I go to the Jotul old stove owner manual page (on Jotul's US site), there is no link to a manual for the F 3, just for the F 3 CB... But on the company's UK site, there is a manual for the F 3. Then, somewhere else entirely, I found a manual for "Jotul F3 USA." Super confusing.

2. Trying to determine whether it's better to install rear vent or top vent. I have an existing fireplace opening that is 26.5" high. One version of the manual indicated the F 3 could be installed into an opening 25.5" high. Of course, that's the manual I read BEFORE I bought the stove. BUT...the guy who sold me the stove gave me a poorly printed copy of the manual he clearly found on the internet...a different version, for an F 3 CB (which may or may not be the actual stove model he was selling me...?), indicating that 28.5" clearance was needed! When I got the stove home, I discovered that neither of these is actually the case (measuring tape anyone?...duh...). In fact, in order to use my 26.5" high fireplace opening, I'd have to go VERY SLIGHTLY DOWNWARD (we're talking well under an inch) before angling back up, as the top of the rear vent flue is perhaps 27" from the ground. Is this (angling down and then back up) possible? Is it advisable? Would doing this negatively impact draw?

3. If the above scenario is not feasible, I'll have to do one of two things: get a set of Jotul's short legs OR top vent instead. In this case, I'd abandon the idea of using the existing fireplace opening altogether and instead extend a double-walled pipe indoors for 6-7 feet, then go into the wall (which is brick masonry, with an unlined masonry chimney just behind it) 8" from the ceiling. Is it better, from an efficiency/heating standpoint to have stovepipe inside the room, rather than going directly from the stove into the chimney? Does having an indoor pipe add significant heat to the room? Are there compelling reasons NOT to do this? Seems like chimney/pipe cleaning would be more complex...? What about draw...is it affected by this consideration?

4. I have a masonry hearth pad thingy (build into, and essentially at the level of, the surrounding pine floor -- see attached photo), that may have been adequate for the fireplace but is JUST big enough to accommodate the footprint of my new stove. Given my height constraints, how do I achieve adequate floor protection WITHOUT raising the stove up any higher? And if I end up having to install Jotul's short feet on the stove in order to use my existing fireplace opening, will I need a higher degree of protection, and if so, how do I achieve that? The different manuals don't agree on the point of floor protection. In the (F 3, not F 3 CB) manual I found on jotul.co.uk, it reads: "Jøtul F 3 has a heat shield underneath which protects the floor from radiation. The product can therefore be placed directly on a wooden floor that is covered by a metal plate or other suitable, non-inflammable material. The recommended minimum thickness is 0,9 mm." provided the bottom heat shield is in place (is the heat shield the ash pan, or is it a separate part?). But in another version of the manual, it says "floor protection under the Jotul F 3 must be any non-combustible material with an insulative R Value of 1.1." Nowhere in either manual does it mention how the amount/type of floor protection needed might differ if one were to swap out the tall feet for the short feet. And how the heck do I know if a given material, or set of layered materials, gives an R Value of 1.1? Is a simple steel sheet adequate, and if so, how thick, and does it need a sublayer of something else? I think sheet steel would look best...

5. What exactly am I protecting my floor from? Just embers? Or combustion via overheating? I know this is pretty basic, but it's damnably difficult to find reliable information in these days of mostly plagiarized internet drivel. I suspect someone on here can explain this, and many other things, to me in 5 minutes, whereas an internet search only leaves me gnashing my teeth and tearing my hair.

6. Does R value of a material change if that material is compacted -- say I use some squishable material of the proper R value (or higher), like an inch thick layer of kaowool, but put a metal plate on top of it, thereby reducing its thickness to 1/4" or less?

7. In the photos, you'll see that there is a wooden mantel-like projection above the stove. It protrudes from the wall 3" and is 8" above the top of the stove. In the event that I can't get proper clearance, either from the stovetop itself or the indoor stovepipe (if I opt for top venting), is there some (not horribly ugly) way I can protect the wood? Sheet of steel? Sheet of steel offset a distance from the wood (that is, with an airspace behind it)? I have the ability to cut and weld sheet steel, so that's not a problem... I do realize I may have to pull the stove out a bit more from the brick wall/fireplace in order to get more clearance between stove/pipe and mantel...which then probably puts my stove feet on wood...complicating things further. But I think I can deal with all that, if I understand the basics (as above).

8. Are there compelling reasons NOT to use flexible chimney pipe? My masonry chimney is unlined, and flexible seems like the easiest thing to install. I simply don't have the cash to pay someone to do the install, so it's on me.

JOTUL f3  close.jpg Jotul f3.jpg
 
Yes, that looks like an F3CB, but could be an F3 international. They are both 27 7/8 high. The top of the rear flue outlet is 25 9/16" so theoretically, that should just work if the lintel height is 26.5". the flue should never go down hill, it should have at least a 1/4" rise / ft. to the liner tee.

Floor protection under the Jøtul F 3, must be any continuous non-combustible material with an insulation R value of 1.1. This is more than just ember protection. I can't say if the fireplace hearth is proper or not. there should be no wood or combustibles underneath it. If that is the case, then a simple hearth extension pad with the right insulation value can be placed up against the legs, under the ashlip as long as it provides at least 16" of protection in front of the door.

At 8" the mantel is very close to the stove top and rear exit pipe. This is a hot area. Even with shielding, this is a dicey clearance.
 
The F3cb has a stainless steel baffle. Do you have that?
 
It looks like there is one in there. The F3 international has this too.
 
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What I would do. Get short legs, xxxxxx rear vent to a t into to an insulated flex liner. Add appropriate hearth xxxx pad With R value xxxxxx so the stove will be out infront of the fireplace about where it sits now.
 
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This is a tiny fireplace. It barely looks wide enough for a stove. I'm just seeing the fireplace opening or sign of a lintel in the pictures provided. Radiant stoves are not the best solution in this case. The low mantel is also still a concern.
 
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This is a tiny fireplace. It barely looks wide enough for a stove. I'm just seeing the fireplace opening or sign of a lintel in the pictures provided. Radiant stoves are not the best solution in this case. The low mantel is also still a concern.
Yep need to look at all these pictures closer
 
Yes, that looks like an F3CB, but could be an F3 international. They are both 27 7/8 high. The top of the rear flue outlet is 25 9/16" so theoretically, that should just work if the lintel height is 26.5". the flue should never go down hill, it should have at least a 1/4" rise / ft. to the liner tee.

Floor protection under the Jøtul F 3, must be any continuous non-combustible material with an insulation R value of 1.1. This is more than just ember protection. I can't say if the fireplace hearth is proper or not. there should be no wood or combustibles underneath it. If that is the case, then a simple hearth extension pad with the right insulation value can be placed up against the legs, under the ashlip as long as it provides at least 16" of protection in front of the door.

At 8" the mantel is very close to the stove top and rear exit pipe. This is a hot area. Even with shielding, this is a dicey clearance.
Ok, that makes sense: install a hearth pad up to/against, not under, the legs, overlapping the existing hearth. With short legs (if I go that route), will I likely need a higher R value? I would think so, but it would seem that the manual would indicate this if it were the case, but I can't find any reference to a higher degree of floor protection with short legs.

The flue should never go downhill. Good to know -- thank you!!

About the mantel: so you think I need to pull the stove out so that the mantel is 20"+ from the stove top (diagonally speaking)? The F3CB manual lists the following clearances (remembering that the "mantel" in my case only protrudes 3" from the brickwork, making it deeper than the "maximum top trim depth", but not nearly as deep as a normal mantel, and is situated 8" above the stove top vertically):
Top to Mantel 34” 860 mm
Top to Top Trim 20” 510 mm
Maximum Mantel Depth: 11 1/2” 292 mm
Maximum Top and Side Trim Depth: 1 1/2” 38 mm

Of course, these clearances assume the stove is directly below the combustible mantel/trim, and my stove, even if not moved, is below and in front of the mantel beam, not directly below it.

Any ideas for how I could shield the mantel well enough (instead of moving the stove out so much)? I read the alcove installation part of the manual, hoping I would find something there, but they don't mention shielding above the stove. And, as I say, the mantel/beam thing isn't actually above the stove (it would be above the rear exit pipe, but I could use double-walled and get away with this small clearance, right?). Sounds weird, but I could install a sheet metal shield of angle iron with some sheets of Micore or similar beneath, rather than just having an airspace...I have no idea if Micore would actually be better than air.

Now, don't laugh too hard: would it be a seriously bad idea to remove the wood beam and fill in the gap with masonry? The fireplace has a steel lintel across the top of the opening. Is the wood beam serving as a sort of lintel as well? I've never seen a lintel that wasn't just above the firebox opening, which makes me think this wooden beam is merely decorative, somewhere to set the framed family photos.
The F3cb has a stainless steel baffle. Do you have that?
The baffle is not stainless, unless I'm very much mistaken. It's matte black (but then maybe stainless can get that way inside a stove), and it's highly magnetic.

But because of the obvious need for higher rear-vent clearance, I can only draw the conclusion that this is an F3CB. Does that seem right?
This is a tiny fireplace. It barely looks wide enough for a stove. I'm just seeing the fireplace opening or sign of a lintel in the pictures provided. Radiant stoves are not the best solution in this case. The low mantel is also still a concern.
I don't quite get your meaning. The stove would be placed in front of, not inside the fireplace. The stove, in fact, would not fit inside.

"Radiant stove are not the best solution in this case." What do you mean? Sorry, lots of dumb questions. I guess I don't know any other options, and...I already have this stove. Is it going to be super inefficient for some reason, and simply not worth installing?


Then also, I'm still wondering:
Is it better, from an efficiency/heating standpoint to have a vertical length of (double wall) stovepipe inside the room, rather than going directly from the stove into the chimney? Does having an indoor pipe add significant heat to the room? Are there compelling reasons NOT to do this? Seems like chimney/pipe cleaning would be more complex...? What about draw...is it affected by venting position?

Thanks for your replies. And sorry for the stupidly long delay in my response. I actually didn't know I had any responses for a few days! I'm new not only to this forum, but to forums in general.
 
I don’t think the wood mantle is structural, there should be a metal lintle on top of the fireplace fire box. Is there brick behind the mantle? What holding it there? If it were me I’d remove it or raise it up higher.
 
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Double wall stove pipe will be pretty insignificant heat wise but it may draft better. It will also cost more.

Your little radiant stove should be fine imo especially if it sits out in front of the fireplace. Adding a metal block off plate in the throat or damper area of the fireplace around the liner will help with heat lose up the flue.
 
New here, so bear with me...and I thank anyone in advance who has the patience and temerity to read through and respond to my grueling list of questions.

I'm looking for advice before installing a new (to me) Jotul F3, rear vent into an existing fireplace opening (or possibly top vent, up higher in the masonry chimney).

I've found at least 3 different manuals for apparently the same stove model, all differing in installation advice/clearances/efficiency/etc. Or maybe I just think it's the same stove model? The numbers and letters are baffling to me, even after reviewing Jotul's identification graphics. (The plaque on the back of my stove simply identifies it as an F3, but it has a curved door handle, so it looks to me like an F3 CB as shown in the identification graphic.)

Couple/few questions:

1. Can someone clear up for me whether the F 3 and the F 3 CB are in fact the same model? When I go to the Jotul old stove owner manual page (on Jotul's US site), there is no link to a manual for the F 3, just for the F 3 CB... But on the company's UK site, there is a manual for the F 3. Then, somewhere else entirely, I found a manual for "Jotul F3 USA." Super confusing.

2. Trying to determine whether it's better to install rear vent or top vent. I have an existing fireplace opening that is 26.5" high. One version of the manual indicated the F 3 could be installed into an opening 25.5" high. Of course, that's the manual I read BEFORE I bought the stove. BUT...the guy who sold me the stove gave me a poorly printed copy of the manual he clearly found on the internet...a different version, for an F 3 CB (which may or may not be the actual stove model he was selling me...?), indicating that 28.5" clearance was needed! When I got the stove home, I discovered that neither of these is actually the case (measuring tape anyone?...duh...). In fact, in order to use my 26.5" high fireplace opening, I'd have to go VERY SLIGHTLY DOWNWARD (we're talking well under an inch) before angling back up, as the top of the rear vent flue is perhaps 27" from the ground. Is this (angling down and then back up) possible? Is it advisable? Would doing this negatively impact draw?

3. If the above scenario is not feasible, I'll have to do one of two things: get a set of Jotul's short legs OR top vent instead. In this case, I'd abandon the idea of using the existing fireplace opening altogether and instead extend a double-walled pipe indoors for 6-7 feet, then go into the wall (which is brick masonry, with an unlined masonry chimney just behind it) 8" from the ceiling. Is it better, from an efficiency/heating standpoint to have stovepipe inside the room, rather than going directly from the stove into the chimney? Does having an indoor pipe add significant heat to the room? Are there compelling reasons NOT to do this? Seems like chimney/pipe cleaning would be more complex...? What about draw...is it affected by this consideration?

4. I have a masonry hearth pad thingy (build into, and essentially at the level of, the surrounding pine floor -- see attached photo), that may have been adequate for the fireplace but is JUST big enough to accommodate the footprint of my new stove. Given my height constraints, how do I achieve adequate floor protection WITHOUT raising the stove up any higher? And if I end up having to install Jotul's short feet on the stove in order to use my existing fireplace opening, will I need a higher degree of protection, and if so, how do I achieve that? The different manuals don't agree on the point of floor protection. In the (F 3, not F 3 CB) manual I found on jotul.co.uk, it reads: "Jøtul F 3 has a heat shield underneath which protects the floor from radiation. The product can therefore be placed directly on a wooden floor that is covered by a metal plate or other suitable, non-inflammable material. The recommended minimum thickness is 0,9 mm." provided the bottom heat shield is in place (is the heat shield the ash pan, or is it a separate part?). But in another version of the manual, it says "floor protection under the Jotul F 3 must be any non-combustible material with an insulative R Value of 1.1." Nowhere in either manual does it mention how the amount/type of floor protection needed might differ if one were to swap out the tall feet for the short feet. And how the heck do I know if a given material, or set of layered materials, gives an R Value of 1.1? Is a simple steel sheet adequate, and if so, how thick, and does it need a sublayer of something else? I think sheet steel would look best...

5. What exactly am I protecting my floor from? Just embers? Or combustion via overheating? I know this is pretty basic, but it's damnably difficult to find reliable information in these days of mostly plagiarized internet drivel. I suspect someone on here can explain this, and many other things, to me in 5 minutes, whereas an internet search only leaves me gnashing my teeth and tearing my hair.

6. Does R value of a material change if that material is compacted -- say I use some squishable material of the proper R value (or higher), like an inch thick layer of kaowool, but put a metal plate on top of it, thereby reducing its thickness to 1/4" or less?

7. In the photos, you'll see that there is a wooden mantel-like projection above the stove. It protrudes from the wall 3" and is 8" above the top of the stove. In the event that I can't get proper clearance, either from the stovetop itself or the indoor stovepipe (if I opt for top venting), is there some (not horribly ugly) way I can protect the wood? Sheet of steel? Sheet of steel offset a distance from the wood (that is, with an airspace behind it)? I have the ability to cut and weld sheet steel, so that's not a problem... I do realize I may have to pull the stove out a bit more from the brick wall/fireplace in order to get more clearance between stove/pipe and mantel...which then probably puts my stove feet on wood...complicating things further. But I think I can deal with all that, if I understand the basics (as above).

8. Are there compelling reasons NOT to use flexible chimney pipe? My masonry chimney is unlined, and flexible seems like the easiest thing to install. I simply don't have the cash to pay someone to do the install, so it's on me.

View attachment 321234 View attachment 321235
5. What exactly am I protecting my floor from? Just embers? Or combustion via overheating? I know this is pretty basic, but it's damnably difficult to find reliable information in these days of mostly plagiarized internet drivel. I suspect someone on here can explain this, and many other things, to me in 5 minutes, whereas an internet search only leaves me gnashing my teeth and tearing my hair.

///you are protecting for sparks and heat 18 IN front 8 each side///

6. Does R value of a material change if that material is compacted -- say I use some squishable material of the proper R value (or higher), like an inch thick layer of kaowool, but put a metal plate on top of it, thereby reducing its thickness to 1/4" or less?

//use something called k board // it has a low r value/// or look at cement board to see if it is ok in the installation Manual////

7. In the photos, you'll see that there is a wooden mantel-like projection above the stove. It protrudes from the wall 3" and is 8" above the top of the stove. In the event that I can't get proper clearance, either from the stovetop itself or the indoor stovepipe (if I opt for top venting), is there some (not horribly ugly) way I can protect the wood? Sheet of steel? Sheet of steel offset a distance from the wood (that is, with an airspace behind it)? I have the ability to cut and weld sheet steel, so that's not a problem... I do realize I may have to pull the stove out a bit more from the brick wall/fireplace in order to get more clearance between stove/pipe and mantel...which then probably puts my stove feet on wood...complicating things further. But I think I can deal with all that, if I understand the basics (as above).

////// yes but a metal shield will give you a 50% reduction/// this still will not be enough//

8. Are there compelling reasons NOT to use flexible chimney pipe? My masonry chimney is unlined, and flexible seems like the easiest thing to install. I simply don't have the cash to pay someone to do the install, so it's on me.

///// no you should use a flexible liner with base tee////
 
5. What exactly am I protecting my floor from? Just embers? Or combustion via overheating? I know this is pretty basic, but it's damnably difficult to find reliable information in these days of mostly plagiarized internet drivel. I suspect someone on here can explain this, and many other things, to me in 5 minutes, whereas an internet search only leaves me gnashing my teeth and tearing my hair.

///you are protecting for sparks and heat 18 IN front 8 each side///

6. Does R value of a material change if that material is compacted -- say I use some squishable material of the proper R value (or higher), like an inch thick layer of kaowool, but put a metal plate on top of it, thereby reducing its thickness to 1/4" or less?

//use something called k board // it has a low r value/// or look at cement board to see if it is ok in the installation Manuel////

7. In the photos, you'll see that there is a wooden mantel-like projection above the stove. It protrudes from the wall 3" and is 8" above the top of the stove. In the event that I can't get proper clearance, either from the stovetop itself or the indoor stovepipe (if I opt for top venting), is there some (not horribly ugly) way I can protect the wood? Sheet of steel? Sheet of steel offset a distance from the wood (that is, with an airspace behind it)? I have the ability to cut and weld sheet steel, so that's not a problem... I do realize I may have to pull the stove out a bit more from the brick wall/fireplace in order to get more clearance between stove/pipe and mantel...which then probably puts my stove feet on wood...complicating things further. But I think I can deal with all that, if I understand the basics (as above).////// yes but a metal shield will give you a 50% reduction/// this still will not be enough//

8. Are there compelling reasons NOT to use flexible chimney pipe? My masonry chimney is unlined, and flexible seems like the easiest thing to install. I simply don't have the cash to pay someone to do the install, so it's on me.///// no you should use a flexible liner with base tee////
What stove is this for? Most of your questions will be answered in the stove manual.

Yes a flexible liner is fine but there are multiple types of flex liners some are better than others and all should be insulated
 
Yes, if you compress material its insulating value decreases. Put r19 glass fiber in your 2*4 wall cavity, and it won't be r19 anymore because you had to compress it.
 
1/2" cement board on top of 1/2" Micore or 2 layers of 1/2" Durock Next Gen cement board will get you there.