Never been to Pennhurst specifically but this kind of thing comes up a lot with caretaker buildings and servant quarters. There's something about spaces where people lived in a kind of isolated, low-status way that seems to hold energy differently than the main building. I've noticed it at a few locations out here in Nevada too.
What did it feel like for you - more like pressure, or more like being watched? That distinction matters a lot when you're trying to work out what you're actually dealing with. Pressure sensations near old cottages can sometimes be explained by the building settling or underground water, but the "watched" feeling is harder to dismiss.
Anyone else who's done Pennhurst I'd genuinely love to hear what area affected you most. The cottage or the main asylum wards? From what I've read the whole site sits on some interesting geography and I've always wondered if theres a ley line component nobody's properly mapped out yet.