If you model one square meter as the declared unit, and 5% is wasted during A5 installation, do you then have to model 1,05 m2 in A1-A3?
If yes, what if you don’t model A4-A5? Do you then only model 1 m2 in A1-A3 (making the two LCAs incomparable)? 
Hi,
Thank you for the question.
Yes, if 5% is lost during installation, we have to add this extra material that has to be produced. The extra material is considered in A5. Our OCL software does this automatically. You define the % of installation losses in A5 query and it directly takes a X% of A1-A3 in A5 as input. Then the waste/output has to be modelled also A5.
If you don’t include A4-A5, then installation losses are not considered.