A common complaint about green building techniques is that they increase the cost of the building. While this is sometimes the case, often it is a matter of higher up front costs, to achieve a lower upkeep cost. However, many green building techniques can be achieved with no price increase. This is collection of such ideas. Mail more suggestions
A smaller building requires less materials, less energy to keep comfortable, and is cheaper to build. Unfortunately, reducing a dimension, reduces the volume as he cube of the change, and the surface area by the square of the change. Volume is what you use; surface area is what you pay for. This means that each reduction in sizes benefits you less, though it is still a benefit. For example reducing your linear dimensions by 5%, will reduce your cost by almost 10%, but will reduce your available volume by about 15%. Heat loss is also based on surface area, so it helps with energy bills as well.
For most building materials, the rectangle is the most efficient shape. Corners are expensive to build, and reduce efficiency, and generally weaken the envelope. Costs for a linear foot of perimeter are about 5 times the cost for a square foot of floor area.
An example: a house 25 * 40, each square foot of floor area might cost say $100, so (by the equation above) each linear foot of exterior wall might cost $500, for a projected cost of $165,000 (130 linear feet @ $500 + 1000 square feet @ $100). Thus, adding a 10 x 10 bump out to the house will increase the cost by $20,000. While adding that same 100 square feet at one end, will increase the cost by only $14,000. Or alternatively, putting the same $20,000 into an increase in the length of the house will get you 143 square feet of area.
Passive solar heating (and cooling) is easier if this simple rule is followed. You want to use true south not magnetic south1. Slight deviations are not too critical however.
This is based on your climate and other factors. The trade off is between surface area and volume. Victor Olgyay2 gives the optimum ratio of long side to short as follows:
A south window is almost always a win (except perhaps in cooling only climates). Its heating profile matches the desired one (ie. it lets in more heat in winter and less heat in summer) unlike windows in the other directions (including southern skylights) which all let in more sun in summer than winter.
A properly designed overhang will shade southern windows in the summer, and allow sun in during the winter. The proper amount of overhang is dependent on the climate and latitude.
Make sure that you use all the volume you (and the environment) are paying for. A majority of the house plans I have seen commonly available, have wasted space, inefficient space, badly designed space. Hallways, for instance are generally useless, and they take up not only their space, but also the space needed for the walls. Every space should have a reason. Walls take up between 0.4 and 1.0 square feet for each running foot of wall.
Modern open plans are more efficient with modern heating styles (i.e. heating the whole building to roughly the same temperature). Modern insulation levels make this more likely as well. Closing a room off from the rest of the house, as was done in earlier days, wastes the thick insulation, and basically makes your uninsulated inner walls into outer walls.
If you can get materials and at the same time preventing something from going to the landfill is a double win. From using old barn boards to dumpster diving for construction materials that others are throwing away, it all helps and allows you to build cheaper. There are websites which list materials available for reuse; find one near you.
Using local materials has several advantages. One, you are paying for material rather than paying to ship that material across the world. Two, the materials will be more in keeping with local vernacular architecture.
If you have a limited budget, make sure to use what you have to do those things which you won't be able to do later. You will only get one chance to insulate the foundation, do it now. The money it saves you in heating and cooling can be put to use to do the things you put off.
Clothes you already own, are free insulation, so are books. Plan for closets and boookcases to be on the outside (preferably North since it will have fewer windows) wall. If your house is low on insulation, and you can't afford more, foam packing peanuts work well. For an attic space, fill boxes with them, and make a contiguous layer of them on the attic floor. They can have stuff stacked on top if you desire.
Garbage disposals waste water, energy, composting resources, and most importantly, space in you septic tank, and leach field or municipal sewer system. The price for a new leach field is thousands of dollars, and require digging up a (new) section of your lawn. Garbage disposal might reduce the useful life of a leach field by half. Get a compost bucket for the kitchen instead. I have friends in the city who export their compost bucket to friends who have a compost pile (or use one of these composters.)