When attacking the defending units use weapons with the least possible damage to buildingsBeorntheBold wrote:
How can I best ensure the least damage possible?
-- however that will be at the expense of your units then, because ranged weapons cause higher building damage than melee units .. 
..but it will even (randomly) caused damage if you take a province without a fight -- so it doesn't really matter much to pay attention to it, you can not prevent it (simulates a kind of "scorched earth").
.. little hint: you can (sometimes try to) wait until the province has an industrial complex at level 2, so you don't have to repair or even build new the expensive first level .. 
