Dave Page wrote:
The Natural Philosopher wrote:
Lobster wrote:

When topping up old insulation (Rockwool) it's normal and more
effective to lay the second layer perpendicular to the first.

I think you mean 'orthogonal'

Perpendicular is walls... ;-)

I understood what Lobster meant, and feel that "perpendicular" was quite
appropriate. After all, laying insulation foam vertically wouldn't make
sense.

It would - but it tends to slide off
I'm wondering ATM if any of the common '270mm' rolls of stuff on the
market can be split into 3 or 4 parts - for insulating the garage.