Well, there are a few things that you haven't mentioned. You said it is a new house but is it being built right now or do you buy the house right after it was built? If you bought if after it was built, it should have insulation in it already. If not, I would contact the builder. All that aside, the first thing you need to do is to determine what the recommended R value is for the area in which you currently live and how much insulation you will need. If you won't need a lot of insulation, then go with the rolls of fiberglass insulation. If you have a lot of insulating to do, then the spray foam is a good idea. As far as faced versus unfaced, I've never actually heard that faced provides a great vapor barrier. You have a better chance using the foil faced type because there's less of a chance to moisture getting into the insulation. Faced insulation also gives you flaps that you can use to staple the insulation to the roof rafters inside the attic. The best way to prevent moisture is to make sure you have adequate ventilation around the insulation. The attic floor isn't that much of an issue. You can roll batts of insulation into the space between the joists to give you around R 30 or so, depending on what zone you live in.Whats the best way to insulate a new house? face od unfaced? or the new foam product?
The foam product, icynene, is the the best insulating product I have ever come across. It fills all gaps more thouroughly than any normal batt insulation, this means there are no ';cold spots'; in your wall. The only off-gas is water vapor so it is environmentally friendly and safe for the house. The product is an open-cell insulation which means it doesn't hold water like batts and is more resistant to mold and mildew. The main drawback is the cost. This is not a DIY project and should only be done by certified installers. The return on investment from energy savings, however, is very short only a couple years I believe. The link below should have better info on that. I highly recommend it.
Faced creates a vapor barrier to protect your house ffrom excess moisture. if you use unfaced you'll still need something to create a vapor barrier. The foam sheeting has a much lower R-value (insulating power) so I would definitely stay away from that on any exterior walls.
Spray in foam does have definite advantages over conventional fiberglass in that it seals every little nook and cranny tight so less infiltration, mice and bugs hate the stuff.
Foam also tranfers heat and cold much less than fiberglas because of the uniform and dense packed foam capsules or bubbles in the foam itself.
Conventional foil backed fiberglass is good and more cost effective initially but degrades and mice and bugs like it plus it has less insulating value per inch of depth than foam.
Overall, the foam insulation would be the better way to go.
http://www.icynene.com/
This is a good site that tells you the advantages of foam insulation.
