libraries are subject to DBE. they are not affected by BE though so always calc it as 100 BE when you are using the forumula. for example you have 10% libs and 80 BE. you use this formula to figure out what the building will give you

Percentage Based Buildings = Base Effect * BE * % of building * (100% - % of building)

on normal buildings where it says BE you put in whatever BE you have so the less BE you have the less effect the building will give. however libs are unaffected by that so always calc it as 100 BE. even if you have more or less. they still suffer from DBE though.