One of my favorite chapters in Bill Mollison's Introduction to Permaculture was the one on housing.  In addition to all of the mainstream information on passive solar (with or without an attached greenhouse), closing and opening windows to manage air temperature, thermal mass, and shade trees, he introduced a concept I'd never heard of --- the shade house.

A search of the internet suggestions that Mollison's shadehouse may sometimes be known as a lathe house.  Regardless of the name, the structure is placed on the north side of the home in our hemisphere, has a partially covered top to provide shade, and is coated with vegetation inside and out.  Vines are often trellised up the sides, and the top may be made of trellis material to allow the vines to continue their growth there, or it might consist of multiple layers of snow fencing or one layer of reflective shade cloth.  Water tanks inside or around the structure can provide extra thermal mass.

The shade house produces a very cool environment to feed air into the house in the summer.  Opening a high window on the opposite side of the house (or a vent in the top of an attached greenhouse) lets hot air escape, then a vent low in the wall attached to the shade house pulls in cool air from that structure to replace the warm air.

A shade house also provides other much-needed uses on the summer homestead as well.  You can add an outdoor bathing station, and should definitely consider raising mushrooms there and rooting cuttings in the shade.  We've yet to find the best environment for mushroom logs in the summer, and although my cuttings do pretty well in the semi-shade of the porch edge, I can see how a shade house would make propagation even easier.

The one thing I'm unsure of is whether a shade house would make the main house too moist in our wet climate.  Constant rain during summers like this one mean that fabrics left to dry over chairs in the house often mold before the water leaves them, and swamp coolers definitely won't work on our humid farm.  Part of the benefit of shade houses is supposed to be adding humidity to the air, so maybe they're not compatible with our area after all?