Selecting and Utilizing a Site
Not having a good building site constrains everything else you do, so in that sense its the most important decision you will make. Everything else you do in building relates to the site and the sites micro climate. This is a concept that anyone who thinks about solar power is very familiar with, but that few others even think about. Zoning laws enforce how land is used, but unfortunately they're mostly about imposing uniformity rather than allowing each lot to have the things it needs, like light & privacy. In fact, the way urban areas are laid out makes it nearly impossible for every lot to get the sunlight it needs.
1) Finding a Site
Every real estate agent will tell you that value is just location,
location, location, although from a green building perspective, the market is
currently under valuing some of the aspects of location, and overvaluing others.
While neighborhood type, views, and access to services and schools are often
still important factors, walkability, safe bicycle routes, access to sunlight,
noise, traffic, and sense of nature are often very important for green building.
Rather than a list of amenities, if you think in terms of the house as being part of both an ecosystem and a community, the question to ask before buying is "Do I want to live in that ecosystem and that community?" Some negative characteristics can be gotten around with house and landscape design, but difficult problems like darkness and excess traffic noise are always a challenge. Cost and availability often are significant barriers to getting an ideal location, so compromises will often have to be made.
It is best to know the limitations of the site before you even design anything. Here are some things that are often important:
Sun: good sunlight exposure allows for 25-50% of a buildings heat needs to me met for free, so a dark site throws away energy and money.1
It's more than just energy though, because most people like to be in the sun, and daylighting inside is also important. Given a choice, afternoon shade is generally better than morning shade, and deciduous shade is better than evergreen or shade from hillside or other buildings.
If you need winter heating, you want sun most of the day. In the summer, and in hot climates you want to be able to hide from the sun, especially in the afternoon. Daylighting is always desirable, likewise a spot outside that is in the sun during the right season.
Neighborhood: For many, neighborhoods are about status, but for many green building people, its mostly about community. In some wealthy neighborhoods, its seems the gardeners know each other more than the occupants. Community is about working together and being together in a way that makes people feel connected instead of isolated. People are inherently social animals, so when everyone keeps to themselves, they tend to feel isolated.2
In a city, a good neighborhood is walkable, either via sidewalks or pedestrian and bike paths, creating opportunities for chance meetings, while in a rural area it may come more from depending on each other.
Neighborhoods, mostly only urban ones also need green space: not just ball fields, but natural green space where you can relax. A good neighborhood has a grocery store, post office, bank and other commonly used services within walking distance: it is the one reason urban living can be more "green" than rural living.
Living in the country all too often means giving up the ability to walk because the roads are too narrow, there are no parks and trespassing is frowned upon.
Quiet: No one really likes noise, especially car noise, which is pretty universally disliked. If a street is just a little busy, you can mitigate the sound of the cars to some degree with plants and thick, tight walls. Loud traffic noise, or airport noise, or other industrial noise is much harder to mitigate. Running water has been used in public parks, but on a residential scale, if you have to pump it, the energy use will be quite high, and not everyone finds the sound soothing.
View: the ability to look out over the neighborhood, or at water, or mountains is a great feature, but it often expensive. Homes located on hilltops are often windy and tend to feel exposed to the elements. Partial views can be a nice compromise.
Transportation: the ability to do some chores by walking or bicycle reduces the stress of driving. In that sense more compact neighborhoods often allow for more services to be available within a shorter drive. If there is functional public transit, easy access to it is a plus. In general the further out you are in suburbia, the more you'll have to drive, and these days the traffic is often as bad or worse than in cities where road systems have been improved over time.
Existing conditions: If your buying an existing house, keep in mind that homes in disrepair are usually overvalued because people grossly underestimate the cost to remodel. A house with charm, but no insulation and leaky windows may be great to look at, but isn't that nice to live in. Most houses are built with only considerations of the number of rooms, structural issues, cost issues, and building codes, so keep in mind that you'll either have to live with the layout, or face a potentially costly remodel.
It is almost always better to build on a disturbed site (ie already used) than to build on a site that has never been built on. There is little natural land left, so the more wild the site, the less desirable it is as a building site. If you must, minimize the impact.
2) Lot Size
A lot needs to be big enough to give you privacy from your neighbors,
but not so big that you're isolated from them. In the city, the ideal lot
is probably not much smaller than 5000SF and probably not much bigger than about
8000SF. The caveat to this is that row house can take up a lot less space,
but when that is done, a suitable amount of natural green space must be left so
that everyone has access to a place to connect with nature. In Radburn,
NJ, each single family detached house has a very small lot, but they all open
out into a large common green, giving everyone the feel that their lot is very
large.
An argument could be made that 5000SF is actually too big because lots built that size almost always end up with "dead spaces" that are too dark, not private enough, not wide enough etc, typically in each side yard. These spaces add no value other than maintaining a psychological distance from neighbors. Another alternative is arranging lots so that there is only a very thin passage on the north side, and no windows, so the home to the north can utilize most of the space as part of their south yard.
For those that want to live in the "country", a much larger lot is needed, big enough that the neighbor's house is a walk away and that you have room to grow food, cut wood, and still have space left for wildlife, probably not less than 40 acres, and maybe as much as a few hundred. Those "horse acre" or "ranchette" lots are nothing more than a way to chew up the countryside without and redeeming features. They're too small to function as true country living, and too far away to create a real city neighborhood. If you look at old small towns all over America, you'll find that the houses are always tightly gathered together as dense as in most cities.
3) Locating the building
In the city you will rarely have much choice of building site, although
on larger lots you can shuffle the house a few feet in any direction.
Uniform zoning setback often prevents you from making the best use of a lot, for
example if the street is to the north, then the yard is only a buffer between
you and the street and you want most of your outdoor space in the back where
there is sun, but zoning laws generally won't let you move the house any closer
to the street on the north: the front yard becomes a dead zone. On the
other hand, zoning allows houses to be as close as 10 feet apart on the side,
which means that if one is north of the other, the southern house can almost
completely block the sun to the other house, which is a tragedy.
For those who have a few acres, especially if there are quite a few, there is an additional emotional component of deciding which locations are cherished, and possibly sacred and which are less so. Contrary to what is often done, the best place for the house is typically the least nice place on the lot. Walking around the bare land, and looking at if from the perspective of which place are you willing to lose to development, this approach makes more sense.
The contrary argument is that people want to be able to look at, or out from, the nicest spot. This is understandable, but the downside is that you've now put a building right next to that nice spot. Imagine how horrified you'd be, if the nice spot was on your land, and the house belonged to a neighbor. Consider also, whether you're the neighbor who built next to, or spoiled the view from someone else's favorite spot. There is often a compromise location, still nice, but one that is not an eyesore from everywhere else.3
Assuming you do have some latitude, here are some things to consider:
Sun: locate the house so it gets enough sun, and if summer shading it needed, try to place the house so it gets summer afternoon shade. Since shady outdoor spaces aren't used in most climates (hot being the exception), push the house as far north as reasonable, leaving the south side for porches, patios etc. In hot climates, face the house east if possible, or otherwise hide the west face from the hot afternoon sun.
Trees: mature trees are a wonderful asset, but placed wrong they can block solar gain during the wrong part of the day, and lower the output on both PV and solar hot water systems.
Neighbors: an ideal location makes is so that you pass each other by, but you don't look into each others houses. This can be fixed somewhat with fences and hedges, but big barriers tend to create a sense of isolation. Its probably obvious, but people generally don't like houses, trees, or fences shoved on them.
Connection to site: eventually you want to think about what each room will be looking out on. The common areas want more connection to the street, while private areas want more to look out on green with a lesser connection to the street. The building needs to be integrated into the site so that it becomes a part of it. This is partly done by choice of site, and partly by building outdoor spaces on the edge of the building that act as transitions between the building and the site.
Connection to the street: you want to be connected, so that guests can find you, and so you can connect with neighbors, but far enough that privacy is maintained. How will the walk from the street go? Where will the driveway be (if any)?
Hilltops: the best view might be on top, but it's also the place of the most wind. Houses on hilltops are not only exposed to the weather more, but they look unnatural. Dropping the house down 30 or even 50 feet, preferable tucked into a little alcove will not only make it feel much more protected, but it will keep everyone from having to look at it.
Critical areas: Avoid areas that flood, or are subject to landslide. In general avoid riparian corridors, as they are best left for wildlife. Good farmland is best used for food: avoid building on fertile soil. Never build on the best soil: instead build on the area of worst soil.
Views: in rural areas where sweeping views are available, the best building site is usually not in the place of the best view, but rather at some compromise place that has a good view, but is more protected from the elements, and doesn't stick out like a sore thumb in your neighbors view.
Dead Spaces: in urban areas you often get "dead spaces": places that are too small, lack privacy or are too dark. Think about landscaping and how outdoor spaces will be used and try to find a use for everything.
4) Building Orientation
In most climates it makes sense to orient a building, so that the longest
face is to the south (ie build on an east/west axis), to maximize the amount of
daylight and also passive solar gain. It isn't critical that this be the
case, but you have to work hard to get the equivalent light and heat if you
don't orient it this way.
In hot climates, a north-south orientation can be better is the west sun is blocked by a hillside or other permanent barrier.
Notes
1: in climates with long hot summers, a bit dark, especially to the west can be advantageous, but typically shaded sites are more prevalent in climates where they're not so desirable.
2: admittedly few people living in those kinds of communities who would say they felt isolated. The people who do report it have generally moved elsewhere.
3: no matter how beautiful you think your house is, others are not likely to agree if it spoils their view.