Our DD is also at a BH and has similar problems napping there. Right now, for example, she regularly takes two naps at home with me, totaling about 2 hours, whereas at daycare she regularly will take only one nap that lasts between 20-45 minutes. This type of thing has been going on since she started at 5 months (home: 3 naps, totaling 3 hours; daycare: 2-3 naps, totaling 1.5 hours, and sometimes even less).
The issue for our DD is that she has always been super alert and curious. She has always had trouble settling to sleep when there were things to look at/noises.
We kept her at BH because her teachers were awesome and she was otherwise thriving. That type of environment is perfect for her because there is always something going on. To be honest, I think she gets bored at home on weekends, even though we play with her and take her on outings.
She is about to transition into the toddler room, so I'm hoping that the daily quiet nap time will help her sleep more.