Best fibre insulation on the market?

[ashthekid]

In my conversion project we have had to create a sizeable cavity in the walls between the 9inch thick brickwork and studwork on one side and a very thick chalk cob wall and studwork on the other side. The cavity is approx 300mm.

The spec'd plan is to have 100mm rigid insulation between the vertical studwork and then 50mm rigid insulation over the inside, 25m battens and then 15mm soundbloc plasterboard.

I'd like to find out what the best fibre insulation I could put inside the cavity space up against the studwork for additional heat insulation. The contractor has suggested a 100mm fibre layer.

 

Any thoughts or recommendations on what could be used that won't break the bank but improve the U-Values.

[Mr Punter]

Something quite rigid like Rockwool slab?

[ashthekid]

Does that have a good U-Value compared to other options?

[A_L]

34 minutes ago, ashthekid said:

Does that have a good U-Value compared to other options?

 

As good or better than any other fibrous insulation and a better 'bang for the £' than PIR/PUR/Phenolic 'plastic foam' types.

[TonyT]

Plus it’s a known product for builders to fit.

not many trades doing CPD 

 

no taping of joints required which the builder will unlikely carry out to a good standard.

[Moonshine]

if you really have a 300mm cavity i would look at 200-300mm of dritherm 37 or similar material

[Mr Punter]

1 hour ago, Moonshine said:

if you really have a 300mm cavity i would look at 200-300mm of dritherm 37 or similar material

 

With a chalk cob wall I would want a decent cavity.

[ashthekid]

Has anyone used or recommend SuperFoil SF60 Multi Foil Insulation?

 

Technical Info
Polypropylene reinforced heavy outer laminated foil : 2 layers
Aluminium coated reflected foil PET layers : 20 layers
Thermo foam separation layers : 24 layers
Loft quilt 80g/sqm layers : 9 layers
Total layers : 55 layers

Specification
Hot box conventional 'R' value : 4.643
Thickness installed : 100mm
Total area pre roll : 12sqm

 

[LA3222]

3 minutes ago, ashthekid said:

Has anyone used or recommend SuperFoil SF60 Multi Foil Insulation?

 

Technical Info
Polypropylene reinforced heavy outer laminated foil : 2 layers
Aluminium coated reflected foil PET layers : 20 layers
Thermo foam separation layers : 24 layers
Loft quilt 80g/sqm layers : 9 layers
Total layers : 55 layers

Specification
Hot box conventional 'R' value : 4.643
Thickness installed : 100mm
Total area pre roll : 12sqm

 

If you do a search of this forum for this type of insulation there have been a fair few discussions and it generally gets described as snake oil. I'm no expert but that reads like a bit of tinfoil, a bit of foam and a bit of rock wool. My preference would be 100mm of PUR insulation.

[A_L]

13 minutes ago, ashthekid said:

Hot box conventional 'R' value : 4.643

 

That value requires a 25mm air space on both sides of the insulation. 200mm of fibrous insulation will have an equal or better thermal resistance at half the price. Then there is the question 'does it actually work?

 

https://www.superfoil.co.uk/wp-content/uploads/2020/10/5575ps1i1.pdf

[ashthekid]

Ok so scrap the SuperFoil. Sounds like a bad idea.

 

So Rockwool RWA45

or

Rockwool Thermal Cavity Batt

or

Knauf Dritherm 37
Or another alternative?

 

Is that about the best option for maximum thermal and acoustic insulation?