Insulating external section of a stud wall

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zbed

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I've taken down one side of a stud partition in the lounge of my victorian terraced house.

The partition was empty, as I expected, apart from one section that had half a brick wall built within it, sitting directly on top of the floorboards.

I realised that the other side of this particular section is the external 'open porch' type bit of the house. So the bricks were probably put there for insulation? But only half way up?? :?:

So I want to insulate the top half and down the left side of the bricks, as there is literally only about 3cm of lath & plaster to the outside world.

Any recommendations? The width of the stud wall is about 6.5cm, might be able to squeeze 7cm in if I use something spongey.

fm88zo.jpg
 
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Hi there,

not sure if the bricks are going to give much insulation against anything.
Can't you stud the lot out and use some 100mm thermal board and maybe a vapour barrier? You'd be snug as a bug then. 50mm thermal board might give sufficient insulation, depending what you are using the room for, but the more you put in the less your heat losses will be and once you've done it it's not easy to change your mind.
 
Seriously,,, The other side of that studwork is the outside of your house?. Something very amiss with that.
 
Yes. Seriously!

At first I couldn't work out why there were bricks in the cavity. I started pulling them out (a lot were loose) but luckily got distracted before trying to smash the rest out. Then, when later doing some measuring up in the hall (the other side of the main section of the stud wall) I realised what was going on.

What can I say, it's a 120yr old worker's cottage that was built as cheaply as possible.

Regarding the thermal board - I can't use that sort of thickness over the top of the studwork. The room is tiny, to lose even 50mm would be a big impact. Especially coz I don't actually need it for the rest of the wall, only that one 18" wide section that's external.

That's why I'd rather just fit something in the cavity - would Celotex (cut to sit as close round the bricks as poss) be appropriate?

I realise there'll be a cold bridge where the bricks are, but it'll be an improvement on what I've unknowingly lived with for 5 years.
 
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If you want to use every available mm which seems a good idea in your case, I'd suggest getting oversize fibre-wool and then compressing it into the cavity.

Don't know if there are still subsidised offers available but obviously look out for those .
 
Is that the stuff you use in lofts?

I've got a few unused rolls sitting in the loft from the previous owner.
 
Yes

Even though you may be squeezing it ( depends on thickness ) may be a good idea to tie/pin /staple at the top to prevent "slumping"

You should put a continuous plastic sheet between the plasterboard and the insulation to prevent condensation forming.
 
Will the condensation then not just form on the plasterboard?
 
It may not be an issue here, but you will want to be careful with moisture.

If it is an external wall, that is just rendered stud work, there may be some moisture penetration. The lack of insulation actually protects it in a twofold manner, first heat loss through the wall keeps it dry, and secondly water can dissipate through evaporation on the inside face.

If seen a few cases where insulation such a wall negates these effects and then causes excess moisture to build up in the wall.
 
If you do lots of moisture-creating things like drying clothes inside, yes it will but for normal living unlikely.

Look at this to see how temperature difference/humidity inter-act to cause condensation.

http://www.dpcalc.org/

This is in any case better than the condensation happening in the fibre-wool as that will dramatically diminish the insulating properties.
 
So would I be better to use and insulating material that also allows moisture to pass through it?
Click to expand...

The normal answer to this is "NO' because the water won't conveniently pass through and condense the other side but condense where it reaches the "Dew-Point" ( look at the previous link I gave you ). If this happens to be inside the insulation then the condensation forms there, the fibre gets wet and loses 90% of its insulating properties.

There are claims made for sheeps-wool but I have no knowledge of how true they are.
 
Better off with Celotex and a polythene vapour barrier.
 
Joe

Celotex is rigid and will not allow him to use every mm of space,. Apart from that he has previously said that he has rolls of fibre-wool in the loft.
 
But it's a much better insulator than rockwool.
 
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