I'd guess that the vamps are effected by the UV aspect, otherwise they'd be able to walk about freely as long as it was cloudy.
I can imagine Kuruno setting up the lamps in his house, then the vamps just blow the shit out of it with AKs and other automatics.
"Beer is the mind killer. Beer is the little death that brings total obliteration. I will face my beer. I will permit it to pass over me and through me, and when it has gone past I will turn the inner eye to see its path. When the beer has gone there will be nothing. Only I will remain."
Make beer, not war.