ᐅ 280 mm insulation, top floor ceiling with 260 mm joists

Hello everyone,

Does anyone have a tip on the best way to insulate my top floor ceiling (new build)?
There will be 260mm (10 inches) high collar beams installed, but according to the calculation, I need to install 280mm 035 insulation.

Ideas so far (please provide feedback/criticism):

- Adding boards along the beams and installing 180mm + 100mm insulation
- Adding boards along the beams and installing 280mm insulation (280mm insulation is expensive)
- Adding layers across the beams: 160mm + 100mm between the beams and 20mm across the beams (24mm battens)
- Adding layers across the beams: 260mm (more expensive) between the beams and 20mm across the beams (24mm battens)

Many thanks in advance for your help.
Best regards,
Johnny77

Hello
Option 3
even though there are no huge differences
Cost-effective insulation and the beams insulated from above



Olli

Instead, use 260mm WLG 032? It's a bit more expensive, but you won't have any hassle with doubling up or fiddly work...