The difference between Celotex Insulation & Fibre wool?

[Jged]

Hi,

Can anyone tell me please what the difference is between Celotex insulation and fibre wool insulation?

I recently moved into an apartment and used http://www.sitesnagging.co.uk to carry out an independent inspection who were very good at what they did but who pointed out that no insulation had been installed in the loft.

The developer did agree to fit the insulation that had been overlooked and put in some fibre wool. However I have read that the NHBC have suggested that it should be Celotex insulation instead? I'm not even convinced that they did a proper job of it? Can anyone please advise me on the difference between the types of insulation.

Any help appreciated,
Jged

 

[freddiemercurystwin]

Generally rockwool or fibreglass insulation, which is presumably what you mean, would only be used in a new build above a top floor ceiling in a conventional house. It sounds like your developer/builder has just shoved some in to appease you.

That said, if it were properly supported/adequate thickness it would be acceptable to use it in this situation and that would need to be determined before it was condemned.

Generally something like Celotex or Kingspan would be used for the walls & pitched roof in such a development as it is a rigid foam (think polystyrene but a better insulator) as its self supporting and is cut with a saw or knife.

Rockwool or fibreglass is floppy and a poorer insulator so it won't support itself and needs to be a lot thicker.

You'll have to be more specific as to what thickness have been used and where for any more guidance? Is this a new build or conversion or what?

If they 'forgot' the insulation, one could rightly be concerned about what else they 'forgot'! These 'builders' should be shot!

 

[^woody^]

Quilt is not "poorer" than Celotex, it is just less efficient heat insulator at the same thickness. Rockwool is fire resistant too, whereas Celotex it's not. Rockwool has better sound resistance at a given thickness too.

It is better to lay quilt in a roof space, as it will more likely fill gaps than can be done with rigid board such as Celotex

 

[freddiemercurystwin]

Quilt is not "poorer" than Celotex,

Oh FFS don't be so feckin pedantic!

 

[^woody^]

How is fibre "poorer" than Celotex in terms of fire and sound resistance then?

 

[freddiemercurystwin]

in terms of heat insulation, pretty obvious really

 

[tony1851]

Have you two EVER got on?

 

[^woody^]

Have you two EVER got on?

Who says we don't

FMT likes me to keep him on his toes

 

[theoldun]

Hi,

Can anyone tell me please what the difference is between Celotex insulation and fibre wool insulation?

In a nutshell.
To achieve current u value of 0.16Wm2/K

270mm thick Earth wool, Rockwall, Fibreglass with a lambda of 0.044 W/mk will give R value of 6.13m2k/W and U value of 0.16Wm2/K

140mm thick Celotex with a lambda of 0.022 W/mK will give a R value of 6.36m2k/W and will also give a U value of value of 0.16Wm2/K

With the exception of sheeps wool celotex is approx twice as efficient as earth, rock or glass

Fire risk and acoustics do not come into the equation.
Regards oldun

 

[JohnD]

That's handy, have you got a link to a calculator?

I think I have about 160mm fibreglass and want to top up with foam slabs so I can put the flooring on top, I want it to be equivalent to the 270mm standard.

Or can I just say (270-160)= 90mm fibreglass = 45mm (say 50mm) foam slab?

I might use polystyrene as it is cheaper than Celotex.