Is this mould?

[damson]

Hi all

We had the attic bedrooms in our dormer chalet bungalow skimmed (to cover Artex) 3 years ago. The dwarf walls are made of concrete blocks and are one block thick - they support the roof. There's a triangular shaped attic space behind the dwarf walls. There are two dormers in each bedroom - the window only opens in one of these. In both bedrooms we've noticed slightly darker spots have appeared on the interior surface of the dwarf walls (see pictures) that were re plastered. It looks a bit like someone has sprayed lemonade on the wall but the spots are a bit bigger - the size of a pea maybe. There are also a few spots on the top of the side of the dormer wall in one bedroom (on the hinge side). One bedroom (the worst affected) is painted with breathable eco paint, the other with cheap white emulsion.

Are these spots due to mould? And is it the cause likely due to condensation (rather than damp) as all bar the dormer wall are internal walls which adjoin the attic? I wondered if it were due to poor air circulation as the spots appear mainly behind or next to furniture and we do have issues with overheating in the summer.

Confirmation that this is mould much appreciated!! And what to do about it - am checking out the wiki links for heritage-house.org as we speak.

thanks in advance!

Untitled

• damson
• 5 Nov 2014
• 1

Untitled

• damson
• 5 Nov 2014
• 1

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[AronSearle]

I wondered if it were due to poor air circulation as the spots appear mainly behind or next to furniture and we do have issues with overheating in the summer.

Yes = Condensation/damp/mould

More ventilation will fix this issue, and leave some air space between furniture and exterior walls for air to move around.

Adding more insulation to the walls and roof is the better long term solution, as this will reduce the coldness of the walls, and reduce summer overheating.

 

[damson]

thank you Aron

Would leaving the windows open in the day be sufficient do you think - or do you think we should leave them open at night too?

I wanted to build a fitted wardrobe along one of the dwarf walls - do you think this is now advisable? Or would it be OK if I fitted insulation behind all the dwarf walls in the attic (there's 10cm of celotex in the roof part of the rooms) but insulating the dwarf walls is a nasty job because the attic space is so small. I was thinking of using something pleasant to use - based on sheep's wool or similar. Any suggestions?

Finally - should spraying vinegar do the trick to remove the spots or are they ok from a health perspective (we have asthma sufferers in the house)

thanks again

Damson

 

[AronSearle]

You would need to insulate the wall before fitting the wardrobe.

You could do it internally with insulated plasterboard, and lose some space.

Otherwise you would have to have vents into the wardrobe to prevent condensation and mould.

It is happening because you walls surfaces are cold relative to internal temperatures and humidity, for surface condensation. Leaving them open in the day will allow it to dry off, but it may still form at night as internal temperatures and humidity will rise.

Insulating is better, as sometimes the amount of ventillation needed is relativly excessive to stop condensation forming (this really depends on how much you care about your leccy bills).

 

[damson]

Thanks again Aron

So, are you saying I could use something like this https://www.youtube.com/watch?v=EHMiaVmQOLA Celotex PL4000 to insulate the dwarf walls inside both bedrooms and that should make the rooms both warmer in the winter / cooler in the summer and less prone to condensation/mould?

And I think you're saying as a stop gap/first measure I could just insulate the wall where the wardrobe is going and add air gaps for extra security.

(I'm wanting to get this sorted once and for all - have previously posted about insulating the attic etc //www.diynot.com/forums/floors-stairs-lofts/chalet-bungalow-loft-rooms-overheating.324930/ but never decided on a solution)

thanks again

Damson

 

[AronSearle]

So, are you saying I could use something like this https://www.youtube.com/watch?v=EHMiaVmQOLA Celotex PL4000 to insulate the dwarf walls inside both bedrooms and that should make the rooms both warmer in the winter / cooler in the summer and less prone to condensation/mould?

Yes, if the wall surfaces are warm enough, they will be too warm for condensation. You will need to think about cold bridging (gaps where you have no insulation), as this will create spots where condensation is then more likely to occur (as you have further increased temperature, but still have some cold surfaces). This is mostly an issue around window openings, or at ceiling junctions. The latter is easier to avoid when insulating internally.

Insulating internally will also lower your internal thermal mass, making it easier avoid overheating during dusk/night. Insulating on the outside of the wall, keeping the thermal mass inside, helps to avoid overheating in the day, but creates overheating at night, choose your preference.

And I think you're saying as a stop gap/first measure I could just insulate the wall where the wardrobe is going and add air gaps for extra security.

Yes.

Once the level of insulation is good enough, you will need less ventillation (you always need some).

 

[damson]

Thanks Aron that's very helpful indeed.