Sorry, yes you're right. Wouldn't make much difference, it's just that the joists tend to be 100mm anyway.
I thought it was 100mm between joists then 170 on top?
The two stars relate to the thermal efficiency of the product. This is loft roll 44, there is also a better, more expensive loft roll 40 product. The thermal value (R value) is 0.044 w/mk. To hit current minimum regulations for a new loft, you need a total of 270mm of this. 170mm between the joists, and then 100mm across the top.
What are the two out of five stars on its packaging? Any details on R or U values? Thanks
Great comprehensive post. Thank you