The Psychodidae contain the moth flies and sand flies. We suspect that you may moth flies in the bathrooms of some buildings. The moth fly larvae feed in the pipes on detritus and then emerge as adults occasionally appearing on the bathroom walls. This time of year that would be your best bet. They can occasionally be common around sewers and drains.
Drain flies are a common problem in restaurant sinks and drains, etc.
If fact, they can be a problem in homes as well. If you are interested in psychodids, I would contact an entomology department at your local university or check out the biological sciences library for information. Also, you might try contacting a local pest control operator for specific information about finding drain flies in your local area. We are experiencing some of these tiny pests in several areas and would like your advice on handling this situation. If you have correctly identified the offending dipterans as phorids then it is likely they are coming from decaying vegetation.