"Enclosure" and "shelter" are nuanced words. Some enclosures are more porous than others. Some shelters are more sheltering than others. It seems we need more words, different words to describe the many varying degrees of enclosure and shelter that we find and create in the world.
An arbor, attached porch-like to a home, can offer an airy enclosure or shelter that treads lightly and doesn't impose. It creates an ambiguous indoor/outdoor space. If it were planted with a grape vine or wisteria (as in this Ask Katie example), the additional shade and denser boundary would feel more sheltering and perhaps softer. Bare bones as it is, here, the arbor creates interesting shadows and patterns that delineate and suggest a porous enclosure and shelter. Without the arbor transition between house and deck, the inside and outside realms would be all the more separate.
by Katie Hutchison for House Enthusiast