Internal and external insulation

[carljarrett]

Hi all, I have not been able to find this answer anywhere… can you do both internal and external insulation on solid brick walls. My plan is 75 mm  external insulation and then silicone render but also batten and insulate internally with kingspan 25 m phenolic insulation on battens off the wall.. Will this cause condensation/damp/ventilation issues?

 

thank you 

 

[Iceverge]

What kind of external insulation at you using? 

 

Are you planning on leaving an air gap behind the phenolic insulation internally? 

 

Can you fit more externally?

 

 

[Conor]

Makes a lot more sense just to put 100mm on the outside.

[MikeGrahamT21]

Technically it is possible, and called Hybrid Wall Insulation (and can even combine IWI,CWI and EWI, obviously you have no CWI but just to illustrate), but its only ever used if there is a reason for not installing more EWI.

 

If you do use HWI, one side of the insulation will need to be breathable, whether that be inside or out to prevent trapping moisture.

[carljarrett]

Hi all.

 

I have built a timber framed second floor and gable to gable roof with a roof room on top of my bungalow. I have already has to overhang the timber sole plates and put a larger cavity on the new walls just to get enough overhang to account for 50 mm external insulation downstairs, This is why i want to insulate internally in the bungalow aswell as 50 mm externally. I will be battening the inside walls and then putting the phenolic on top across the battens, so there will be a void behind them to breath. Is this ok ?

[carljarrett]

External insulation will be the standard polystyrene type i guess to render onto