My neighbor down the road a bit has a terrific trellis arrangement that helps out both in the summer and in the winter, and looks very nice to boot.
They have a large south facing porch across the back of their home, and put in an open roof structure and trained vines to cover the roof and some of the vertical surfaces. The vines provide some very welcome shade on the porch during the summer and also shade some of the south facing windows. In the winter, with the leaves gone, the area under the trellis gets filtered sun that is very pleasant to sit in on sunny days when the full sun might be a bit to bright. The windows behind the trellis also get some winter solar gain through the vine branches -- this can be adjusted by pruning. In the fall, the vines put on a very nice fall color display.
The vines take some time to get established -- they thought about 5 years to get to full coverage. And, some trimming and pruning is needed each year to keep them in the areas you want. They have trained the vines to cover both the roof surface and some of the vertical surfaces where they wanted sun protection.
The roof structure is just open 2 by lumber supports spaced around 2 ft apart with chicken wire between to support the vines.
Lots of pictures below:
Click on pictures for full size
Gary November 23, 2008