The lovely and modern green Matchbox House in Australia by the Bureau for Architecture and Urbanism is all over the blogs these days. It is a lovely thing, but it reminded me of a comment made when I showed SoHo Architecture's House Bru 1.25 earlier:
What ever happened to roof overhangs? Now it is true that in both of these houses, the walls are clad in the same material as the roofs. Water getting on them isn't going to do too much damage.
In Peter Legge's absolutely stunning Connemara project in Ireland, where it rains a lot, the architect has gon to great lengths to integrate a trough into the roof design so that here doesn't have to be anything hanging out, but goes for the no-overhang look even though stone walls could use some protection and shelter.
Roof overhangs do an important job, in keeping water and snow away from the walls and windows; the more the merrier.
In Quebec, where there is a lot of snow and roofs are steep, they even do a belle curve at the bottom of the roof so that the overhang actually hangs out enough to give some protection.
Roof overhangs don't only protect the walls, but they are very useful in green building; if you design them properly they keep the sun out in summer and let it shine in during winter. They are an important part of passive design. There is no reason not to have them on modern houses; it just seems to be an architectural meme that is going around. I am not sure that it's a good idea.