As Mr. Standart and others have said we know the doors were open and the portholes were opened. What made it even worse on the Britannic was that the nurses had opened up the lower row portholes to ventilate the wards because of the weather. When the ship developed her extreme list those portholes were exposed to the sea pretty much at once unlike Titanic from what I could gather. But comparing Titanic to Britannic is kind of an apples vrs oranges thing. Lots of different factors in play. According to the gentleman's article below they did try to close the doors for the boiler rooms but for some unknown reason they failed. You can read the article yourself if interested. But in case your not I'll post a pic from it. It's one I don't recall ever seeing before. From the SS VESTRIS sinking in 1928. Cheers.
T he Britannic departed from Southampton for Moudros at 2.23 p.m. on November 12, 1916. According to Captain Barlett's official report the ship was carrying 1065 people (673 crew, 315 RAMC, 77...