How well does vermiculite insulate compared to fibreglass, PIR, etc?

[Oxbow16]

Hi all

 

I've already got vermiculite in the loft, but only to 100mm or so (varies quite a lot)...  I'm currently reboarding beneath my header tank and got a few other jobs to do up there, but will soon want to add additional insulation.  

 

Does anyone know how vermiculite performs compared to the usual suspects?  I've had a quick look online and come up with nothing so far.  It would be really helpful to know so that I can decide what else to add up there, where to put what, etc.  

 

Many thanks for reading.

[Ian]

It has a thermal conductivity of 0.063 W/mK.

article about its insulation value & cost compared to loft roll insulation here:

https://www.thegreenage.co.uk/micafil-loose-fill-loft-insulation/

[JohnMo]

The lower the thermal conductivity the better.

 

Glass wool at 0.04, performs approx 30% better for the same depth.

 

I would look to add another 200 to 300mm of mineral or glass on top

 

[Conor]

Don't touch the vermiculite. Removing loose insulation is a fool's game. Trust me, I've done it. Stick 300mm of mineral wool on top and job is done. You'll need loft stilts/legs if you want to use the space for storage. Not too big a job - there's plenty of topics on it here if you search.

[JohnMo]

B&Q or Wickes, or similar are usually the cheapest place to buy

[joe90]

Interesting article, slightly less insulating than rockwall type stuff but 8 times the price!