At our Zen temple, we just dealt with this question. The temple has a handful of residents, so it’s a home as well as a temple. For decades, we had no formal policy on whether to allow sex within the walls; some married couples have been residents in the past, so it’s not that we believed sex never happened there, or that it was illicit in any way.
But in the end, we decided to write into the code of ethics that sex is not allowed within the walls. This has nothing to do with sacredness of the temple, nor is it meant to imply that there’s anything inherently corrupt about sex. No one feels that whatever sex has occurred there in the past has degraded the temple in any way.
We did this for one reason. We see the temple as a place dedicated to helping people develop a particular skill: non-attachment. In Zen terms, non-attachment doesn’t mean maintaining an emotional distance; it means avoiding the kind of ego-driven acquisitiveness that is at the root of all kinds of craving. We feel that it’s helpful if we make it explicitly clear that this is the frame of mind with which everyone should enter the building. If people entertain even the possibility that this could be a place where cravings can be indulged, then we begin to lose the benefit of the association of the locale with the mindset of non-attachment. For the very same reason, we don’t serve alcohol or even fancy food there.