swallow nest sites

I work at a wine production site and every year swallows attempt to nest inside a foyer with a roller shutter. They are very persistent and fly in and out all day, but it is not a suitable site as the building has to be secured at the end of the day, and if they get in there is no guarantee they will go out- I don't want a swallow death on my conscience!  I want to provide an alternative- it is such a waste of their energy- but we have no outbuildings that they can enter( Obviously they cannot be where bottling etc occurs.) Is there anything I can put on the outside of the building to tempt them to try their luck elsewhere, or would an outside box be unsuitable? The buildings barely have overhangs. They are definitely swallows not martins! 

sarie