reasonably priced alternative to rockwool

[neilw]

Hello,
To comply with the building regs I need to put in 270mm (well, 300mm is what my building controller wants) of rockwool. I think he's done this because my ceiling joists are 150mm deep. The area is about 12m2.

However, what I want to do is board it out but don't really want to cheat by getting it passed then ripping out 150mm of rockwool (which is what my current loft is from the regs of years ago).

Can anyone recommend a product that'll fit into 150mm with the same thermal values, but isn't prohibitively expensive.

I've been looking around and it's quite hard to figure out the values of insulation for lofts, I think this 270mm equates to a u value of 0.16 or .44w/m2?

I was thinking maybe rockwool slabs might do the job but have no idea of which thickness will do?

 

[PrenticeBoyofDerry]

If you want to board the loft you will need to raise the height of the rafters. This is best done by laying new ones at right angles to the old.

 

[mointainwalker]

1) If cost is a concern, don't look at fibre slabs ( batts ) they are twice the price of roll material and roll is fine for the ceiling and there is no real difference in insulation value.
2) Other material - PIR boards - are 60% better but three times as expensive.
3) The U value of 270 mm of fibre woool is 0.16
4) I don't understand ....... " 0.16 or 0.44 W/m2."

The U value is W/m2/K so a U value of 0.16 is a heat-loss of 0.16W/M2/K

 

[neilw]

The U value is W/m2/K so a U value of 0.16 is a heat-loss of 0.16W/M2/K

I thought the w/m2/k was the r value?

 

[mointainwalker]

No

R value is m2 K/W.

I'm sure that now I've written that, you are slapping your head and saying

"of course, how silly of me "