⁷"Achill Archaeological Field School Achill Island, County Mayo, West of Ireland." Museums of Mayo Network, County Mayo, Ireland. Web. 14 July 2011. <http://www.museumsofmayo.com/achill_1.htm>
The "byre [barn] house" enabled the poor tenant farmer to keep his most valuable possession—his cow—protected inside with him during the winter months. The animals were at the lower end of the slightly inclined floor; their effluent would collect away from the living quarters. There is a good explanation here.