I'm not putting any locks on my vestibule doors. They're inside the building, so who are they going to keep out? Vestibules are usually implemented as a heat/air lock. What are you using yours for?

Personally I would use dummy knobs and ball catches or a passage set on the active door and surface or flush bolts on the inactive door.

I would absolutely have a lock on the vestibule door. This is the door to the outside...correct? Without a lock, someone could wait in the vestibule...either for you to come home or open your interior door. Or, they could have plenty of time to be hidden and work on opening your interior door lock.

I probably sound paranoid, but after an idiot was banging on our front door at midnight (after hitting our house with his truck last November) I was very glad for the lock on our storm door. Not exactly the same, but we certainly wouldn't have opened the main door without it.

Make your guests wait in the weather.

Nice welcome.

Vestibule doors would be inside the exterior or entry doors and in the vestibule to the interior of the home.

Our front door will have a lock. Upon entering the house from the front door you will be in the vestibule, which has a door into the foyer. I'm
Asking if the door to the foyer should have a lock. Thanks.

Well that makes more sense :)

I would say that you don't need a lock from the vestibule into the foyer. Many people use glass in that door...or maybe side lights on either side. It's more of a heat/cold block than a safety feature. At least, that's how I plan to use it.

I can imagine two reasons for wanting some kind of lock on a vestibule door: extra layer of obstacle to keep young kids from escaping outside or to keep them from playing in the coat closet; or to be able to give neighbors a front door key so they could pick up mail/packages while one was out of town and put them in the vestibule, but not have access to the entire house.

Actually, it just occurred to me: my grandparents had a lock in their vestibule door. It was unlocked all day, but we always locked it before heading to bed as an extra obstacle if someone tried to break in; there was a sliding glass door in the back of the vestibule that would have been easy to break and the bedrooms were on the opposite side of the house, so breaking glass might not have been heard. We never locked it when we left the house, just at night. Not sure if there's even a key for it!

I wouldn't bother unless your in a "bad" area or a heavily trafficed one. I can imagine locking myself inbetween the 2 sets of doors and having to navigate the yard in my barefeet and PJ's:)