Best Internal Wall Insulation

[Richyrich1927]

Hi all, I'm doing the bathroom and had to remove the plasterboard so while I have the chance I'd thought I'd insulate the wall.

The wall backs onto cladding and has a polythene barrier with 100mm joists.

What is the best method to insulate this wall please?

 

[endecotp]

For the best thermal properties, use a 70mm solid phenolic or PIR insulation board e.g. Kingspan.
But using 100mm of rockwool, or one of the "natural" products like wood fibre, sheep's wool, etc. you will get better acoustic properties.

Was there nothing at all there before? How old is the house?

Are there any electrical wires in the wall?

 

[^woody^]

Fill between the timbers with whatever depth foil faced insulation you can fit in, and then a minimum of 25mm of the same across the inside face, and then plasterboard. Aim for at least 100mm insulation in total

Extend that window board as necessary.

 

[Richyrich1927]

For the best thermal properties, use a 70mm solid phenolic or PIR insulation board e.g. Kingspan.
But using 100mm of rockwool, or one of the "natural" products like wood fibre, sheep's wool, etc. you will get better acoustic properties.

Was there nothing at all there before? How old is the house?

Are there any electrical wires in the wall?

Thanks for the help, no electrical wires mate, house is 1970's and there was no insulation. Not worried about acoustics as street is quiet. Is it best to part fill or fully fill with 100mm. Should I use a vapour barrier?

Fill between the timbers with whatever depth foil faced insulation you can fit in, and then a minimum of 25mm of the same across the inside face, and then plasterboard. Aim for at least 100mm insulation in total

Extend that window board as necessary.

Thanks for the help, would you use a vapour barrier before plasterboarding or is foil tape on celotex/kingspan enough? how would you secure celotex across the inside face, are screws ok?


Cheers lads!

 

[^woody^]

Make sure the insulation is snug with no gaps anywhere, and as it's a bathroom tape every joint

 

[Richyrich1927]

Make sure the insulation is snug with no gaps anywhere, and as it's a bathroom tape every joint

Will do, thanks mate. Much appreciated.

 

[endecotp]

no electrical wires mat

It's common to leave a gap between solid insulation and the plasterboard for wires and pipes, but if you don't need it then you can fill the full depth (or more, as Woody suggests).

If the rest of the house is similarly lacking in insulation, you should start planning on adding some!

 

[Richyrich1927]

It's common to leave a gap between solid insulation and the plasterboard for wires and pipes, but if you don't need it then you can fill the full depth (or more, as Woody suggests).

If the rest of the house is similarly lacking in insulation, you should start planning on adding some!

Will definitely do the two other rooms with no insulation now. Thanks for the advice mate.

 

[^woody^]

Were there are cables, full fill the insulation, then cut a surface channel into which put some cable capping but reverse it so it's behind the cable and the cable sits in it

 

[Richyrich1927]

Were there are cables, full fill the insulation, then cut a surface channel into which put some cable capping but reverse it so it's behind the cable and the cable sits in it

Good tip, thanks mate.