Closing a 140mm cavity

Ferocious

I’m building with a 140mm cavity (100mm insulation). In relation to closing the cavity around the windows and doors, is it acceptable to use standard L blocks (which project 80mm into cavity) and 60mm of insulation between the inner and outer leafs or should the blocks be built such that the insulation closer is kept to 20mm?
I remember seeing a good discussion here about various details around windows but can't seem to find it now. If anyone can resurrect it I'd appreciate it.
Thanks

sydthebeat

Ferocious wrote: »

I’m building with a 140mm cavity (100mm insulation). In relation to closing the cavity around the windows and doors, is it acceptable to use standard L blocks (which project 80mm into cavity) and 60mm of insulation between the inner and outer leafs or should the blocks be built such that the insulation closer is kept to 20mm?
I remember seeing a good discussion here about various details around windows but can't seem to find it now. If anyone can resurrect it I'd appreciate it.
Thanks

returning 80mm and incorporating 60mm insulation is a better result than returning 120mm and using 20mm.

Ferocious

Thanks Syd. I was thinking that thermally it would be better alright. Surely in terms air leakage, it's the junction between the insulation and the block that matters, irrespective of insulation thickness?

Is there likely to be problems installing the windows?