Rockwool / Fiberglass

hargo

Is there any difference between 8" rockwool and 8" fiberglass for attic insulation?

JamesM

hargo wrote:

Is there any difference between 8" rockwool and 8" fiberglass for attic insulation?

The ITCH :eek:
Jim

I know that's a short answer, but do not ignore the itch factor if you are doing the job yourself !

hargo

Why is one worse than the other?

charlie@w.d

fiberglass comes in sheets and is hard and has to be cut with a saw and is usally fitted into the cavities of walls in timber framed houses and dormer type houses.
rockwool comes in flexible rolls which is rolled out on to your attic floor.

the itch factor would be more on the rockwool but with both you would still be itchy and wear a mask when using both as the stuff u inhale is dangerous. horrible job to be honest

JamesM

Unless things have changed very much in recent years, fibreglass comes in rolls and because it is literly small strands of glass, it should not be handled with bare hands. It can be painfull as well as itchy.
Jim

Mellor

Both mineral wool (rockwool) and fibreglass some in rolls and sheets. Both can be used in the same locations, with the excepting that mineral wool can be used as a fire stop as it is resistant to fire.
In terms of insulation properties,
Glass wool has a thermal conductivity of down to .034W/mK.
Mineral wool is down to .037W/mK.
These are better end of the range and the more standard stuff will have values of .040W/mK (glass) and .044W/mK (rock)
There isn't much in it, but fibreglass is slightly better and s0 200mm of fibreglass is better than 200mm of rockwool from a thermal point of view.

Viking House

Isover (fiberglass) gives a rating of 0.44W/m2k in this link http://www.moyisover.ie/plus%20rolls%20page_feb2006.pdf

Rockwool has a higher specific heat capacity and density so if you insulate your house to the same U-value with rockwool as opposed to fibreglass your heating bills should be about 20% lower is my guess.
There is also an issue with the complexity of the woven fibres in Rockwool versus Fibreglass which makes it hold onto heat better.

Mellor

Viking House wrote:

Isover (fiberglass) gives a rating of 0.44W/m2k in this link http://www.moyisover.ie/plus%20rolls%20page_feb2006.pdf

Rockwool has a higher specific heat capacity and density so if you insulate your house to the same U-value with rockwool as opposed to fibreglass your heating bills should be about 20% lower is my guess.

As I said I was quoting the better stuff. And and also the standard stuff in this one Here Isover gives a rating of 0.040W/mK.

And there is the better product on www.moyisover.ie that had a value of 0.034W/mK. http://www.moyisover.ie/datasheet_2012.htm

EDIT: If you look at the end over the data sheet that you originally posted. The very last line also shows the product I refered to, Metac and the value I refered to 0.034W/mK

I am interested by the idea of a higher specfic heat capicity. Because of this it will heat up slower right, but this means that more energy will be used in heating also. People always mix up and and confuse heat (energy) and temperature. But the slower rise in temp (for the same energy input) might cause a delay in heat loss as it is directly proportional to difference in temp. BUT when heat transfer is calculated the outer and inner temps are taken, and the conductivity calculated. Internal temps are not involved, and any improvement from them (and I agree that SHC would have an effect) would already be included in and improve the conductivity and therefore can't really be counted twice.


Oh and its worth pointing out that rockwool might have products with lower values than i quoted, i had a look around their website, and they were the best I seen. But its not the most user friendly site.