How does one insulate the inside of an external solid wall

[ey143]

Some parts of my house are solid wall. How would I go about insulating the insides of both a solid wall but also a cavity wall using either 25mm or 50mm rigid board insulation.

As most of my house is being remodelled, I am back to the brick anyway. Can I just butt this up straight against the brick work and plasterboard around it or do I need to consider other actions to prevent damp etc?

 

[noseall]

50mm of Celotex type insulation will be enough to bring your solid walls up to latest standards.

This can be fitted either as individual boards fixed mechanically to tanalised battens with plasterboards fixed on top or pre-insulated plasterboards can be fixed in a similar fashion. Or you can dab directly to the wall using the appropriate insulated plasterboard. However, only the battened wall method will allow you to fix a vapour barrier (VCL) behind the plasterboards. The need for a VCL will depend upon your wall construction and its vulnerability to condensation.

 

[ey143]

Hi noseall

Thanks for the reply.
Do you think 50mm rigid board insulation will offer better properties than say rockwool etc type insulation, of say 100mm squashed into a 50mm gap?

Do the Celotex/ Quinn boards which come with foil wrapping on both sides, still require a VCL?

How will I know for sure whether I will need a VCL if the internal skin is brick and the external skin is a mainly brick but in some area grey breeze block?

Thanks.

 

[noseall]

Do you think 50mm rigid board insulation will offer better properties than say rockwool etc type insulation, of say 100mm squashed into a 50mm gap?

No. Compressing air filled insulation is a pointless exercise. You will struggle to compress it in any case without the resulting spring-back causing problems to the plasterboards, especially once they become moistened with wet plaster.

Do the Celotex/ Quinn boards which come with foil wrapping on both sides, still require a VCL?

Yes they do and not necessarily no. As long as you foil tape all the joins and fill any gaps robustly, you should be able to maintain a decent VCL.

How will I know for sure whether I will need a VCL if the internal skin is brick and the external skin is a mainly brick but in some area grey breeze block?

I'm a builder not a designer.
However, things to consider would be location of the insulation regards internally produced condensation i.e. kitchen bathroom etc.
Elevation location i.e. NSEW etc.
House location i.e. coastal or inland or elevated - i.e. on a hill or in a valley.

 

[AronSearle]

If in doubt = VCL, in your situation you can't go wrong putting one in.

I also personally would VCL rather than tape, I am dubious the tapes will stand the test of time.

 

[tony1851]

Some of the insulated plasterboards have their own integral vapour control layer.

 

[ey143]

Some of the insulated plasterboards have their own integral vapour control layer.

Could you point me to any specific example links please?

 

[^woody^]

BASF Neopor Lining

www.toolstation.com/m/part.html?p=19476

 

[ey143]

BASF Neopor Lining

www.toolstation.com/m/part.html?p=19476

Hi Woody - I'm a little confused, sorry, but is that a VPL? How exactly would that item be used if at present I am back to brick walls around the house? Would the builder wrap that around the 50mm celotex boards which are fixed to tanalised battens?

 

[^woody^]

Sorry, its an answer to your thread title, and not to your post about a VPL. Its insualtion

 

[cAtLeYx]

You should ensure that any Vapour control layer is fixed directly behind the plaster board (if this is your preferred route in lieu of foil backed board) should a gap be left between the back of the board and the VCL condensation will form and run between the two surfaces. Best option is a gyp-liner with 50mm insulated, foil backed plaster board facing.

 

[ey143]

Shouldn't we be trying to prevent moisture or condensation from forming on the first place? Or is the argument that it will always form because of the nature of warm air meeting cold near the brick, so in actual fact is it about ensuring you don't get damp seeping through the finished layer but let it linger at the brick level?

 

[AronSearle]

What catleyx says is wrong.

If the VCL is in front of the insulation (warm), then a gap in front of it will not cause condensation. Modern buildings sometimes have plasterboard, then a gap for services and then the VCL and insulation.

The point of the VCL is to stop vapour transmission trhough the insulation into the colder parts of the structure where it will then condensate (though I am not actually convinced it is much of a risk, but there is no negative to installing a VCL).

 

[^woody^]

The point of the VCL is to stop vapour transmission trhough the insulation into the colder parts of the structure

You are wrong, cAtLeYx is totally correct.

Vapour needs to be stopped from getting into the structure, not just parts of it. The barrier should be placed as near to the potential moisture source as possible, which is immediately behind the plasterboard.

 

[AronSearle]

Rubbish, plenty of details you can download on the net if you look showing plasterboard, 25mm battened out service void then VCL.

The VCL needs to be within the warm side of the construction, not *immediatly* behind the plasterboard.

http://lmgtfy.com/?q=service+void+and+vcl