Insert stove -Rockwool insulation OK?

Westford

I've just installed a insert stove (8KW).
Basically I have a gap of about 60mm on either side of the stove, about 100mm behind it. And over it, there's about 100mm - 150mm to the head, and then the space up into the flue gatherer. The alignment of the flue gatherer, and the flue port on the stove, was such that I needed to run about 300mm of flexi-flue (solid flue grade) from the stove to the stainless steel flue reducer (which is inserted into the flue gatherer). This gave be the flexibility to overcome the offset. Anyway, my question relates to the best method of filling these gaps. Most seem to suggest that plain old rockwool is the best for the job, and most easy to fit. So this is what I've done. I've had the stove fired up, and all seems well. There was a little initial discolouration of the wool, where it touched the flexi-flue section, but nothing else. Seems to be fine, but now that I'm about to slab & skim the surrounding wall, and basically seal in the stove, I though it might be good to get the input of some of the experts who post here. I did take another section of the same flexi-flue and split it along it's length, and fix it in place over the existing section of flex-flue...sort of like a second outer skin. Probably over kill.
Anyway...any views are appreciated.

bauderline

What make of stove did you go for and how much did you pay for it if you don't mind me asking ?

I have been looking at the Edilkamin Luce 62 for about 1800 euro.

P.

Westford

It's a Nestor Martin... IT33 (I think).
Cost was around the 1400 mark.

Lightning McQue

Are these closed combustion stoves?

Lightning

Westford

I'm not sure I completely understand what is meant by "closed combustion".
The stove is a dual skin construction... and there are 3 controls on it.
1, governs the mode (wood - startup - coal)
2nd is apparently not really for user control, but more geared towards matching the stove to the natural draft of the chimney (I think).
An the 3rd is the regular damper/air intake control.

gsxr1

I think you need that free air space around your stove.

Rockwool is fireproof.

Westford

I agree that a free space is required... But this is acheived through the design of the stove. basically the outer skin or box of the stove is steel... then the actual stove, or firebox, is within this outer box. But it is sized so that there is a gap or a cavity, all the way around the firebox. The gap is about 50mm. So this gaps provides a route for air intake, and hot air venting (in to the room). It is the gap between this outer box and the blockwork of the chimney breast that I am insulating (to prevent heat entering the walls)....This is where the rock wool will sit.

PeteHeat

Hi,

All Rockwool is not fireproof.

Space is supposed to be left around insert stoves with a vent at the bottom and another at the highest point possible.

The lower vent allows cold air around the stove, the higher vent allows heat to escape back into the room.

gsxr1

PeteHeat wrote: »

Hi,

All Rockwool is not fireproof.

Space is supposed to be left around insert stoves with a vent at the bottom and another at the highest point possible.

The lower vent allows cold air around the stove, the higher vent allows heat to escape back into the room.

Sorry.


I thought rockwool was.
At least Sackcloth and Ashes in Sallins told me it was.

In fact everyone I talked to about said it was.

PeteHeat

Hi,

I have experience of Rockwool actually going up in flames, yes I was surprised too.

All Rockwool products are Fire Rated not Fire proof hence the discoularation around the flexi flue.

I have another customer who ignored Part J of the regulations and allowed the insulation to sit tight to the flue (should be a space of at least 50mm) he was a very lucky man.

As he was driving in to his house he could see wisps of smoke at the eaves of the house the insulation had caught fire his main problem was it was lighting at the bottom on the ceiling.

He managed to get the fire out but caused a lot of damage in the process.

gsxr1

PeteHeat wrote: »

Hi,

I have experience of Rockwool actually going up in flames, yes I was surprised too.

All Rockwool products are Fire Rated not Fire proof hence the discoularation around the flexi flue.

I have another customer who ignored Part J of the regulations and allowed the insulation to sit tight to the flue (should be a space of at least 50mm) he was a very lucky man.

As he was driving in to his house he could see wisps of smoke at the eaves of the house the insulation had caught fire his main problem was it was lighting at the bottom on the ceiling.

He managed to get the fire out but caused a lot of damage in the process.

wow. thanks for the info.

I know of lads who have it stuffed up inbetween there stove flu and clay flu liner.
To seal the gap

I nearly did it myself. Got a reducer instead.

I should inform them to inspect it.

iwb

Westford, I have the IT33 and am pleased with it in general but there is one problem that is quite annoying in my view. The bar (not sure what it is called) which holds in the wood is very low.

We find that in order not to have to stock up the stove every half hour, we need to put a good bit of wood on it and that bar is utterly useless at holding it in. As the fire settles, the blocks fall forward and sit against the door.

Do you have the same problem and if so, have you found a solution? I asked the supplier about it and he said he couldn't see how it could be a problem and didn't have a solution.

Naux

Westford wrote: »

It's a Nestor Martin... IT33 (I think).
Cost was around the 1400 mark.

Westford, Could you PM me the supplier as that sounds like a very good price:)

sunnysoutheast

iwb wrote: »

Westford, I have the IT33 and am pleased with it in general but there is one problem that is quite annoying in my view. The bar (not sure what it is called) which holds in the wood is very low.

We find that in order not to have to stock up the stove every half hour, we need to put a good bit of wood on it and that bar is utterly useless at holding it in. As the fire settles, the blocks fall forward and sit against the door.

Do you have the same problem and if so, have you found a solution? I asked the supplier about it and he said he couldn't see how it could be a problem and didn't have a solution.

We found the only solution to this was to lean the wood backwards as much as possible, also we've started using a mix of 1/3 solid fuel to 2/3 wood. Depending on your draught you may be able to turn the fire right down.

Regarding the original question on rockwool, we have both stoves insulated with rockwool which chars a little on direct contact with the flue but nowhere else. It's important that you don't use fibreglass ( a smell of cat's pee gves this away).

SSE

iwb

Thanks for that. I am very tempted to try to make something up that brings it higher as we use the stove as our only source of heating for the house at the moment, so it is constantly stacked up and burning hard.

Westford

Regarding the issue of the wood falling forward ...
We have noticed this a few times... but as was already suggested, we find that if the wood is position so that it lies away from the doors, it gernerally does not become a problem. Having said that, we only use the stove once or twice a week, so that's might explain why this hasn't become an annoyance yet. We do the same as the other poster said... use wood to get it going... and then drop in a few lumps of coal. After it flames up, we just shut it down, and it's usually good for the evening... But like I daid, it's not our primary source of heat... More away of having an open/visible fire option at the weekend....Without having an open drafty chimney for the other 5 days.

iwb

Thanks again for your replies. I will post back here if I try something.

mchammer

sunnysoutheast wrote: »

Regarding the original question on rockwool, we have both stoves insulated with rockwool which chars a little on direct contact with the flue but nowhere else. It's important that you don't use fibreglass ( a smell of cat's pee gves this away).

SSE

Why would you not recommend fiberglass so strongly - just about to install a 6" flue for a 6kw stove in an existing 8"clay flue asnd was going to use fiberglass to seal around it!!

Thanks
MC

sunnysoutheast

mchammer wrote: »

Why would you not recommend fiberglass so strongly - just about to install a 6" flue for a 6kw stove in an existing 8"clay flue asnd was going to use fiberglass to seal around it!!

Thanks
MC

We were told not to use fibreglass by the stove installer. He said that rockwool is OK, it will char a little next to the flue but it will not burn. Fibreglass is not suitable. You also need to cut back any polyiso insulation well away from the flue and fill the gap with sand & cement.

You probably need to check with the stove supplier to see what they recommend, plus ensure you comply with building regs.

SSE

mchammer

Thanks for that - ended up just using some sand and cement - dry enough mix should hopefull do the trick

Westford

Hi...
Just returning to the topic of the insert stoves. A year on, all is well regarding the insulation (rockwool)... However I have a small problem, and I'm curious to see if it has impacted any of you, and if you have a solution.
It relates to the wall surface around the face of the stove (either side, below, and most importantly above). I was sticking slabs, so when it came to the stove, we simply let the slab run into the edge of the stove... Not quite tight to the edge, just close enough so that when the final frame or flashing of the stove was put on, it concealed the edge of the slab & the gap. The slabs were just skimmed with traditional hard wall skim coat. To be honest we weren't sure what other options there were. In any case our original concerns were proven true, and I'm suffering quite a bit of cracking in the finish coat of the wall, due to heat. Most are small hairline cracks, but there are one of two larger ones.... and I expect it to get worse. Not a complete disaster, but it does spoil the clean look of the insert stove.
Any of you come accross this problem... Or used a different approach which has not resulted in cracking. Is there any sort of heat tolerant finish coat that might be more suitable?
BTW...the stove is not in daily use...far from it.

Jack534

Vermiculite is the product for this excellent insulator

PeteHeat

Westford wrote: »

Hi...
Just returning to the topic of the insert stoves. A year on, all is well regarding the insulation (rockwool)... However I have a small problem, and I'm curious to see if it has impacted any of you, and if you have a solution.
It relates to the wall surface around the face of the stove (either side, below, and most importantly above). I was sticking slabs, so when it came to the stove, we simply let the slab run into the edge of the stove... Not quite tight to the edge, just close enough so that when the final frame or flashing of the stove was put on, it concealed the edge of the slab & the gap. The slabs were just skimmed with traditional hard wall skim coat. To be honest we weren't sure what other options there were. In any case our original concerns were proven true, and I'm suffering quite a bit of cracking in the finish coat of the wall, due to heat. Most are small hairline cracks, but there are one of two larger ones.... and I expect it to get worse. Not a complete disaster, but it does spoil the clean look of the insert stove.
Any of you come accross this problem... Or used a different approach which has not resulted in cracking. Is there any sort of heat tolerant finish coat that might be more suitable?
BTW...the stove is not in daily use...far from it.

I already addressed this problem on page one of this thread, part of the reason I don't bother posting advice is I am wasting my time.

The stove is capable of producing 8kw of heat the problem is people expect this 8Kw to dissipate from around the stove using the finishing trim as the point where cool air is drawn in and hot air from around the stove can come back into the room.

The standard installation for inset stoves on the continent is to have an air vent near to the floor on both sides of the chimney and in front of the stove, this allows the cool air to enter and rise up around the stove taking the heat with it, they then have similar vents approximately 1 > 1.5 metres above the stove to allow the warm air out into the room.

Even a standard stand alone stove requires space around it for the heat to dissipate, we advise as near to 150mm all round more if possible.

The way a lot of inserts are installed traps the heat generated in the fabric (blocks, plaster etc) of the chimney which in time causes the finishes to crack and over a longer time and can actually weaken the structure of the chimney.

I brought this matter of the Irish installations up with a manufacturer who has three different installation guides to be used depending on which country the stove is being sold, their answer to get over the problem was to install the liner with no vermiculite or any seal around it allowing the space between between the liner and the clay flue to act as a vent for the heat generated.

Another Irish solution to an Irish problem.

You can get heat resistant plaster board which may not crack but that does not mean the plaster finish won't crack or that the structural block / brick work will not be subjected to extreme temperatures they were not designed for.

Using vermiculite around the stove is not always the answer as it can prevent what little air circulates around the stove at the moment to dissipate the heat.

Chimneys should be designed to allow inset stoves work properly, unfortunately very few can be retro fitted and work the way they should.

.

colyum

Just thought i'd let everyone here know that rockwool is fireproof up to 900c.
Which means you would need to put it into a furnace to burn it.

Glass wool on the other hand is not and burns at 150c.

mike125615

Hi there, hope someone can give me advice before I go totally crazy. I have recently installed a insert boiler stove which gives 12kw to water and 5kw to the room. There is no heat coming to the room at all. Front of stove does not heat up fully I can literally hold my hand against it. It appears to heat radiators OK although the pipe Thermostat does appear to cut out after pump running and then come back on after ten minutes. There is a huge space in the chimney at back of the stove, is this where I am losing all my heat and if it is insulated will it really make a difference?? Help!

PeteHeat

mike125615 wrote: »

Hi there, hope someone can give me advice before I go totally crazy. I have recently installed a insert boiler stove which gives 12kw to water and 5kw to the room. There is no heat coming to the room at all. Front of stove does not heat up fully I can literally hold my hand against it. It appears to heat radiators OK although the pipe Thermostat does appear to cut out after pump running and then come back on after ten minutes. There is a huge space in the chimney at back of the stove, is this where I am losing all my heat and if it is insulated will it really make a difference?? Help!

Hi,

By design the primary job of most boiler stoves (insert or free standing) is to heat the water for the central heating, any excess heat is then sent into the room.

Manufacturers marketing departments tend to advertise the "best situation" performance figure, these figures are based on performance in a laboratory where they use ideal conditions and top quality fuel.

The space behind and around the stove should have been insulated, you may notice the chimney breast gets warmer than you would expect, this would be a sign that you are losing heat to the masonry instead of it coming directly into the room.

Being able to hold your hand on a stove while it is producing enough heat for the radiators is very unusual, perhaps it has a very efficient boiler would you mind letting us know the make / model?

The pipe stat has a differential built in, some can be as wide as ten degrees, basically the stat activates at say 50c and instead of switching of at 49.5c it continues in the on position until the pipe temperature drops to 40c, the pump switches off allowing the stove to build the heat back up to 50c when it activates the pump again.

It is not unusual for a pump to cycle as you describe when the stove is lit and it is building up the heat in the system, the times between the on / off should widen as the system gets up to temperature.

It is possible that your boiler is undersized for your house i.e. not producing enough heat to meet the demand or maybe changing to a better quality fuel will help by producing more heat.

I suggest that you speak to your installer they may be able to point you in the right direction as they know your complete heating system.
.

mike125615

Thanks PeteHeat
I spoke with the manufacturer this morning and didn't tell them about the space at back because I didn't want to give them a excuse. I told them about the poor heat to the room and they informed me that my heat is being stolen somewhere at the back. This could be due to a back draft or opening in the chimney. After this because it corresponds with what I thought I told them about the space and they informed me that I need to close that space with either concrete or Rockwool and this will prevent heat loss at the back and redirect it out the front of the stove. It's a Henley achill 17kw. It does a relatively good job on the rads, I have had it heating seven rads so far and can get up great heat. Those rads are a bit smaller than standard sizes. After insulation thus may also rectify the pipe or boiler cooling and I will post back with results. I wonder does Rockwool lose it insulation value if it is continually heated?

iwb

We have had our Nestor Martin IT33 in for about six years now. We had to take it out recently as the chimney breast cracked and the solution was to put a 6" flue liner in.

I wasn't there when they put in the liner. They told my wife all was good and we could use away on the stove. I lit the fire using wood and all went well. As the heat built up though, there was a strong smell upstairs where we have the 5" pipe off the top of the stove. We assumed it was due to the new install and that something was burning off, sort of like a new oven maybe.

That was over a week ago and we have discovered since then that if the fire is kept very low, there is no smell but once a bigger fire is lit (we always use wood) the smell returns.

One thing I know that is different; They packed the area above the stove with rockwool and I believe that means the area all around the flue, right from the top of the stove. I'm concerned that this is incorrect but would it cause a smell?

lensman

Sorry to drag up an old thread but I have another related question, can you take a look at the pic you'll see I'll have a void between my register plate & the old chimney flue, I plan to fill the gap between the flexible liner & chimney
with vermiculite but what should I do with the void? it would take a
lot of vermiculite to fill this void so looking for other suggestions please, 
I was thinking of wrapping the exposed 6" flexible liner within the void with Rockwool insulation, opinions & views would be appreciated ?

Robert Allen

lensman wrote: »

Sorry to drag up an old thread but I have another related question, can you take a look at the pic you'll see I'll have a void between my register plate & the old chimney flue, I plan to fill the gap between the flexible liner & chimney
with vermiculite but what should I do with the void? it would take a
lot of vermiculite to fill this void so looking for other suggestions please, 
I was thinking of wrapping the exposed 6" flexible liner within the void with Rockwool insulation, opinions & views would be appreciated ?

Can i ask did u manage to solve this problem? Thanks.

dok_golf

Can't speak for anyone else, but I stuffed rockwool into the same void on mine. Without it, there was no draw on the stove. Haven't had a problem in 5 years since