I went to a residential USGBC (United States Green Building Council) Panel Discussion at the Fayetteville Library a few weeks ago and the panel experts talked extensively about green home improvements and green approaches to new construction.
Each panel member agreed that if they had a limited amount of money, and were looking to get the most bang for their buck in regards to energy-efficiency, they would invest their money into insulation and, more specifically, into a thorough caulk and foam job to seal the house.
Canned foam and caulk needs to be used after the framing is complete and before you insulate your home. This can potentially be done by an insulation crew if asked, but they won't perform this step as part of their basic package.
This is an extra step that is not usually taken during construction.
Before insulation and after the framing is done, you can see all cracks, holes, and voids that won't necessarily get filled by the insulation. Your home needs a can of spray foam used around the windows and doors. Make sure it is specifically marked as usable for these two areas. Then, use caulk to go over every seam in the framing. This includes where the floor meets the slab, anywhere there are two studs right together, and where the top of the wall meets the ceiling. The main purpose of filling all of these cracks is to seal all areas where there would otherwise be air leakage. The air will leak through you home if this step in not taken, and most homes built today EXCLUDE this step. (Can you believe that?) It's not considered part of the standard building process to perform this step, and so make sure you ask for it specifically. Insulation can only go so far. To increase the energy-efficiency of your home (or the "R-Value") and to save $$ on utility bills, you need to make sure your contractor takes the time to include this step. All those small holes and cracks do add up. This is just one way to increase your home's comfort and long-lasting quality.