Woodburner - Bad Odour

[Zydas67]

Hello,

 

Replaced my old woodburner with a new Ecodesign model. Work was carried out by a Hetas fitter.

 

Getting bad odour (hard to describe) a bit like burning rubber (plastic?). This happens at around 400C (from the stove thermometer).

 

The opening is boarded out with Knauf Aquapanel (bought from Wickes who recommend it for woodburner installation). The clearance to the back of the stove is around 5cm, so it gets pretty hot there.

 

The fitter advised painting the Aquapanel with exterior paint (I used Sandtex Trade).

 

However, I contacted Knauf who advise Aquapanel is only suitable up to temps of 200C. Also, Sandtex advise NOT using their exterior paint for this purpose.

 

I have reported the problem to the fitter, who has suggested painting over with a high temp paint.

 

Questions (I believe the problem is with the area behind the stove heating up, not the stove which has been properly cured):

 

1. Can the board be painted over, or does the existing exterior paint need to be removed first (and if so, how)?
2. Could it be the Aquapanel giving off the odour, i.e. reaching 200+C?
3. Could it be both?
4. Am I better off getting the fitter to remove the Aquapanel and replacing with e.g. unpainted Vermiculite board (any other suggestions?)?

 

Thanks....

 

 

[ProDave]

 

14 minutes ago, Zydas67 said:

Getting bad odour (hard to describe) a bit like burning rubber (plastic?). This happens at around 400C (from the stove thermometer).

Where is that 400C measured?  Flue temperature?  you don't normally want the flue temp much above 250C

 

14 minutes ago, Zydas67 said:

 

The opening is boarded out with Knauf Aquapanel (bought from Wickes who recommend it for woodburner installation). The clearance to the back of the stove is around 5cm, so it gets pretty hot there.

What does the stove manufacturer say about rear and side clearances?

 

[ToughButterCup]

Mind me asking what you are burning on the stove?  Our next door neighbour burns any old thing (not saying you do) and in a gentle southerly, it honks.

[SteamyTea]

A smell from a wood burner!

"No shit Sherlock"

[saveasteading]

1 hour ago, Zydas67 said:

Am I better off getting the fitter to remove the Aquapanel and replacing with e.g. unpainted Vermiculite board (any other suggestions?)?

I would say yes.  I wouldn't use aquapanel, especially closest to the flue, because it may have waterproofing resins in it, and is not designed for heat.

Likewise sandtex which may have resins/latex/other oils.

I made a flue surround in a wardrobe before it heads up through the roof. About 2m from the stove outlet.

I built a box using lightweight steel angles and boarded it with plasterboard, then stuffed the void with fire grade rockwool, (about 50mm all round). 

Completed the boarding and plastered/filler over it. 

It is barely warm to the touch when in serious blaze mode. No smells, no cracks.

 

[Bonner]

The smell is VOC’s coming mainly off the paint as it decomposes due to excess heat, a health and fire risk. The panel could also be affected as mentioned, who exactly recommended Aquapanel for this application?! Follow the stove manufacturer’s instructions and where they say non-combustible surface, there should be appropriate (uncoated) material such as brick, cement board or slate.

[jamieled]

Are you sure it's not the stove? Normally a new one emits a fairly unpleasant smell until the paint on it properly cures. Most manufacturers instructions I've seen make reference to this.

 

How long have you been using it since installed?

[PeterW]

2 hours ago, saveasteading said:

wouldn't use aquapanel, especially closest to the flue, because it may have waterproofing resins in it, and is not designed for heat.

Err yes it is … Knauf Aquapanel is listed as suitable for enclosing log burners due to its heat resistant properties 

 

Use Knauf AQUAPANEL® Cement Board Indoor when it comes to hot temperatures. Log burning stoves require surrounding walls that can withstand high temperature and are non-combustible. Knauf AQUAPANEL® Cement Board Indoor provides this protection as it easily withstands radiating temperatures up to 200C and is A1 non-combustible to EN 13501-1. It is the ideal substrate for non-flammable and heat resistant surface coatings and finishes as it will not warp, shrink or expand

 

3 hours ago, Zydas67 said:

This happens at around 400C

 

Are you sure that’s not 400°F..??? This is a standard magnetic stove thermometer and the outer ring is °F, the inner is °C

 

 

I would say it’s fairly new and your rubbery smell is just the VOCs burning off the stove paint as it hardens. 

[saveasteading]

3 hours ago, PeterW said:

It is the ideal substrate for non-flammable and heat resistant surface coatings

I stand corrected. Good to know. 

Well done the marketing team that called it Aquapanel. As they only mention it as  a substrate I assume it isn't rated as a fire barrier in itself.

[Temp]

Could it be the stove itself? Most new stoves smell until the paint is baked on. 

[markc]

What was used to fix the aqua panel, I was asked to look at an install causing smoke and fumes …. Cement board had been “fixed” using solvent adhesive, silicon! And packed out with bits of MDF ?

[Zydas67]

Re the stove - clearance from back (from manufacturer's data sheet):

 

"A clearance of 150mm is
required at the back of stove (if the rear
wall has a thickness of 200mm or more
this measurement can be reduced to
50mm)"

 

Mean Flue Gas Temperature - 228°C - Wood

 

I don't believe the odour is the stove itself. During the curing process there was, but no stove manufacturer could sell a stove that stunk so much you had to open windows several months after installing, and make a living. I spoke to them and they said it wasn't the stove.

 

@PeterW - yes correct - exactly same thermometer, so 400F.

 

Aquapanel

 

With the previous installation the fitter used heat proof render. Over time this cracked and pieces fell off. I thought it looked very dry and sandy, and maybe the mix was not right from the beginning.

 

When the fitter he arrived to quote, he noticed damp on the wall in the bathroom (which is due to water getting under the floor lining which has contracted).

 

When he saw the render in the fireplace he said it was damp that had caused it to come off. Maybe he thought there was damp in the whole flat? There is no evidence of any damp, except the bathroom, and the flat had extensive work for subsidence in the 80s, if that's relevant.

 

This meant when I suggested Vermiculite the fitter said it would crumble with the damp etc.

 

I contacted Aquapanel and they said the finish i.e. exterior paint was not recommended and sent the attached sheet. The states that "Tiles must be used to finish the board" (Step 6). 

 

If the flue temp at 30cm above the stove is around 200C (circa 400F), what is the temp of the stove? According to Google - "A standard wood stove will generally burn at between 500 and 800°F". If the top of the stove is at max 800°F I would have thought the Aquapanel 50mm away will be getting very hot.

 

The builders left offcuts of Aquapanel - looking at it, it's made of cement plus embedded sheets of fine plastic webbing.

Aquapanel_behind_wood_burner.pdf

[saveasteading]

5 minutes ago, Zydas67 said:

fine plastic webbing.

Glass I would think, but have not checked.

[Zydas67]

2 hours ago, saveasteading said:

Glass I would think, but have not checked.

 

Correct - have just received the attached data sheet from Knauf. Contains "coated glass fibre mesh".

 

So, why do Knauf have a 200°C limit for woodburner applications? It is described as A1 non-combustible.

 

Melting point for glass is 1400-1600°C. Melting point for silica 1550°C. Melting point for coating unknown.

 

I just burned a piece of the mesh and it lit with a black smoke, leaving the glass behind. The odour was not dissimilar from what I have experienced.

 

But very likely the paint can't take the heat, please see attached. Contains vinyl acetate Veova polymer, which I believe gives durabilty for OUTDOOR uses. I looked up vinyl acetates - boiling point around 135°C (flash point 75°C).

AQUAPANEL_Cement_Board_Indoor_datasheet.pdf MDS-Sandtex Trade High Cover Smooth Masonry.pdf TDS-Sandtex Trade High Cover Smooth Masonry.pdf

[PeterW]

4 hours ago, Zydas67 said:

If the top of the stove is at max 800°F I would have thought the Aquapanel 50mm away will be getting very hot.

Which stove is this ..? Exact make and model please..?

 

Reason for asking is they normally require a minimum of 150mm to non-combustibles and 50mm is very close. 

[Zydas67]

Model is ACR Earlswood III. Please see here for manual https://www.acrheatproducts.com/file/acr/earlswood-manual-ew3mf-0716-2-print-38499.pdf. It has a built in heatshield. On page 5 is states:

 

"A clearance of 150mm is
required at the back of stove (if the rear
wall has a thickness of 200mm or more
this measurement can be reduced to
50mm)"

 

House is a Victorian terrace and there is definitely a thickness of 200mm or more behind the stove....

 

[dpmiller]

Is the aquapanel actually needed in this situation?

[Zydas67]

With hindsight ...No.

 

Hetas fitter diagnosed damp (I believe wrongly). Asked me to get cement board. Aquapanel looked perfect being designed for high moisture areas and also described by Wickes as:

 

"ideal when it comes to withstanding high temperatures making it ideal for use near log burning stoves that require surrounding walls that can withstand high temperature and are non-combustible."

 

But only when tiled ....I didn't realise that, and the builder/fitter didn't say there could be a problem.

[Hobbiniho]

surely the solution is to remove the paint and tile the aquapanel. although you will likely have to replace the aquapanel. The aquapanel is up to the job and as it is a tile backer board buying it and expecting to not tile it is a bit misguided, did you supply and fit the aquapanel or did the stove fitter do it? what warranty did the fitter give you and are any of his recommendations in writing?? 

[Zydas67]

The fitter did everything. I supplied the Aquapanel but the fitter did not mention anything about tiling it. He treated it like normal cement board, and unfortunately recommended the wrong paint also. My preference now is for the fitter to remove the Aquapanel and replace with Vermiculite and leave it unpainted (according to Vitcas painting makes it absorb water). No written warranty but the fitter wants to remedy the situation and Hetas oversee such installations. The fitter wants to paint over with fireproof paint, but this is not a solution, as now I know Aquapanel must be tiled to be used like this.....

[saveasteading]

22 hours ago, Zydas67 said:

and replace with Vermiculite

Good idea. Is this a box-out and if so what material for framing? 

Anything else inside the box you are creating?  If left void, the air in it will be very hot, and so will whatever structure you are using to form a box-out.

I prefer to stuff the void with fireproof rockwool so that the heat goes away and doesn't affect the boxing, as it could distort then leak.

[PeterW]

On 12/02/2022 at 19:32, Zydas67 said:

My preference now is for the fitter to remove the Aquapanel and replace with Vermiculite and leave it unpainted

why not just strip it back to brick and re-point it ..? Or render with the heat proof render ..??
 

https://shop.vitcas.com/fr-fireplace-render.html

[Zydas67]

14 hours ago, PeterW said:

why not just strip it back to brick and re-point it ..? Or render with the heat proof render ..??
 

https://shop.vitcas.com/fr-fireplace-render.html

 

The opening is not centred. When the original fire was fitted there was a step of about 5cm to the render on the right from the edge of the right slip. On the left it is ok, ie. the render (now Aquapanel) finishes flush with the slip. By boarding it out there was no step, which is what I wanted. It looks great, but the materials are wrong. I'm not sure what is behind the Aquapanel on the right to fill the gap, if they filled it with anything (Rockwool?).

[Carrerahill]

On 09/02/2022 at 16:51, Zydas67 said:

Hello,

 

Replaced my old woodburner with a new Ecodesign model. Work was carried out by a Hetas fitter.

 

Getting bad odour (hard to describe) a bit like burning rubber (plastic?). This happens at around 400C (from the stove thermometer).

 

The opening is boarded out with Knauf Aquapanel (bought from Wickes who recommend it for woodburner installation). The clearance to the back of the stove is around 5cm, so it gets pretty hot there.

 

The fitter advised painting the Aquapanel with exterior paint (I used Sandtex Trade).

 

However, I contacted Knauf who advise Aquapanel is only suitable up to temps of 200C. Also, Sandtex advise NOT using their exterior paint for this purpose.

 

I have reported the problem to the fitter, who has suggested painting over with a high temp paint.

 

Questions (I believe the problem is with the area behind the stove heating up, not the stove which has been properly cured):

 

1. Can the board be painted over, or does the existing exterior paint need to be removed first (and if so, how)?
2. Could it be the Aquapanel giving off the odour, i.e. reaching 200+C?
3. Could it be both?
4. Am I better off getting the fitter to remove the Aquapanel and replacing with e.g. unpainted Vermiculite board (any other suggestions?)?

 

Thanks....

 

 

Is it not just the paint/finishes etc. burning off? Very common for a new stove to need a burn in period. After the 2-3 small fires you are supposed to have (after materials have set/gone off etc.) you are meant to have a hot fire and burn off any metal oils, paint finishes etc. Our house had a haze of smoke in it on the first burn in night, opened all the windows, lit it, fired it hard and went upstairs. Second time it did it a little then nothing.

 

Have witnessed this about 3-4 times in my puff now. Normal I'd say. Like using a brand new oven. 

[Zydas67]

Been using the stove for over four months. I agree there was a curing period but that was a very different odour. I contacted the the manufacturer and they said it could not be the stove causing a continuing problem like this..

 

I contacted Knauf re the Aquapanel, and this is the reply:

 

"We have had our SMS dept come back to us and they have concluded that the issue lies with the incorrect finish being applied, ie. painted rather than tiled per our requirements.

 

Please note that as painting is not part of our guidance, they are unable to confirm whether (with suitable adhesive) it would be possible to simply tile over now and that this will resolve the odour issue, whether the paint can be suitably stripped prior to tiling, or if the only recourse would be to remove and replace the Aquapanel Indoor with new."

 

Stripping paint off cement board - any advice? Also, tiling would mean the tiles on the sides would not be flush with the slate slips on either side, and stand proud of the edge, as the Aquapanel was not fitted leaving an allowance for the tile thickness....

 

I would imagine removing the Aquapanel and replacing with vermiculite board would be quicker than paint stripping/tiling, and would not even need to be painted...