The second floor windows are not boarded up. They are shuttered, but they shouldn't be too hard to open. The tough part is that the building does not have any easy way to climb it. The walls are relatively flat with no visible handholds. Possible to climb for an expert climber, but not easy.
While the party is busy dealing with the door, Christina has other plans. Pooh, you stand up and put your paws on the wall under a window and I'll climb on your shoulders and see if I can get one of those window things open. she says.
OOC:
I'm not sure if the action would require a skill check or not.
Bears are 5.6 to 9.2 ft (so Pooh would be close to the maximum) and Christina is 5 foot 2 inches, so they should be able to reach the window.