Bay Window Mould advice

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Hi there,

First post here, despite having browsed multiple times! Thanks to everyone for their varied advice, expertise and knowledge.

Wondering if I could draw on those now, to help me solve an issue with my Victorian, ground floor bay window, which has recently developed some mould on the wall under the windows.

I'm pretty certain that it's a thermal bridging issue - exterior wall without insulation being much colder than the rest of house (double glazing and improved insulation throughout. Still enough ventilation though - aka draughts!)

It only really started showing up since placing a sofa against the wall - I'm guessing creating an air pocket which is encouraging condensation, and therefore, mould.

Wondering what might be potential solutions... I know moving the sofa is the easy option, but I like it there! :D

What about insulating the interior wall? Or will that just move the issue to elsewhere in the room?
And what about heating the wall somehow - a panel heater, or even heated skirting boards (any experience on these?!)

Appreciate any thoughts or advice.

Many thanks.

O
 
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Placing your sofa there has interfered with the air circulation & whether you like it there or not, moving it is the only way to cure it. We have had exactly the same thing on a new wall & I doubt very much that you have any other problem.
 
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Placing your sofa there has interfered with the air circulation & whether you like it there or not, moving it is the only way to cure it. We have had exactly the same thing on a new wall & I doubt very much that you have any other problem.

Yeah, I figured it was the sofa causing the problem. And like you say, I doubt that there are any other problems.

I guess I was just wondering if there was a way to have my cake and eat it, by somehow counteracting the problems caused by the sofa - in my head, that would be by heating and/or insulating... But I'm no thermal dynamics expert!
 

JP_

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Only way is to either move the sofa or insulate the wall a bit. Is there room to move the sofa forward, rather than change it's position? Mould on the wall will get into the sofa if it's too close ...
I guess another solution might be to have an electric radiator on the wall set to a low heat, just to keep it dry.
 
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Insulating the wall will certainly help because you'll lose the cold spot and therefore suffer less from condensation in that area.
 
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Either move sofa or install vent thru wall behind it .
 
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Bays are notoriously badly built often even single skin brick. Given the area the easiest option is to take the plaster back to brick and install either Celotex (50mm) and plaster board or insulation bonded plaster board. Tape and skim the joints and redecorate. It will improve the efficiency by a factor 2-3.
 
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Is there room to move the sofa forward, rather than change it's position?
I guess another solution might be to have an electric radiator on the wall set to a low heat, just to keep it dry.

I can move the sofa forward slightly, possible enough to improve the ventilation behind there, but am concerned about the sides too, where there is less wiggle-room...
Good idea about those slim electric heater panels - I'll look into them further.

... or install vent thru wall behind it .

Hadn't considered putting a vent in the bay... what sort of thing were you thinking? Floor level, under window, or would it have to be middle of wall? Would it vent enough?

Bays are notoriously badly built often even single skin brick. Given the area the easiest option is to take the plaster back to brick and install either Celotex (50mm) and plaster board or insulation bonded plaster board. Tape and skim the joints and redecorate. It will improve the efficiency by a factor 2-3.

This sounds like what I need to hear, and probably the first port of call. Will get started on working out my options for this - thanks.
 
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Had slight mold problem in wardrobe , single brick external wall , 2” round vent was enough to cure it( ventilate ).
 
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Have you seen this thread?
https://www.diynot.com/diy/threads/insulating-a-bay-window-wall-and-ceiling.486785/

Don't forget to insulate the floor void.

I had seen that, but I guess was wondering if there were any more bright ideas around since then! I don't think I have room for battens solution, especially regarding the other-walls question below.

Insulating secondary areas is what I'm working out now... It's a ground floor bay, suspended wooden floor, with parquet. There are two air bricks in the bay, into the subfloor void.

Are you recommending that I insulate under the floorboards? And if so, how far into the room? (That's one hell of a job, and not sure if I can justify it over just moving the bloody sofa!)

What about the rest of the walls in the bay? Can I just insulate the problem area (where the sofa is creating an air trap), or should I be doing all of the exterior bay walls?

Had slight mold problem in wardrobe , single brick external wall , 2” round vent was enough to cure it( ventilate ).

Good to know, I'll look into possible options on that side of things too!

Thanks for everything so far, everyone.
 

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If space is really tight, I'd glue (everbuild pink dryfix foam) 25mm insulation board to the wall - not great thermally, but it should be enough to stop the mould problem. Put a thin plasterboard over and skim, or just paint it if all hidden by sofa.
 
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Definitely don't batten. In the example, the bay is a tiled timber frame (not battens). In your case I'm expecting brick. Celotex PL4000 though quite pricey is the easy option. A Hammer drill with a spade attachment is all you'll need to get the plaster off, a stiff brush and maybe a light coat of PVA, then foam fix or mechanical fix the pl4000 directly to brick and may add one or two frame fixers to hold in place nice and tight (sink them in a few mm under the plasterboard so you can fill the holes, foam fill any joints gaps caused by angles (which will further help it stick). Then tape and finish coat/skim the joints.

I personally would go with a minimum 40-50mm of insulation - its the same price pretty much and you'll find your existing plaster/bond coat is around 20-30mm. So your wall will only take another inch or so off the room. If you have a single skin brick bay then the U-value will be 2-2.5. With 50mm of PL4000, it will be well under 0.5

If you have decent floor down, with a vent, then don't insulate under the floor boards - save that job for if and the floor comes up.
 
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