The floor should be insulated to an R value of 19. This involves getting under the house and putting in rolled insulation. You will need to measure the distance between floor joists to determine the width of insulation to buy.
If insulation with a paper backing is used, remember: the paper goes next to the area being heated ( so next to the floor in this case ). Install the insulation with a staple gun or with wire supports. These can be purchased from any home improvement store, such as Home Depot or Lowes (visit website).
Insulating walls can be a bit more challenging, depending on whether or not you are preserving the original wall material ( plaster, wood, etc ). If the wall is to be removed down to the studs, simply staple insulation between studs before putting up new wall material.
Insulation should be R-23 for walls. If you are keeping the original plaster, then you will want to use a kind of insulation that can be blown into the walls via holes that are drilled outside. Using a machine that can be rented from a home improvement store and bags of loose insulation, fill the walls. Read and follow directions on the product for more tips about this process.
Or, better yet, if you have the room, frame a new wall with studs right over the old wall. Then you’ll literally have a two wall barrier. Although this isn’t necessary to do on all four walls, it can be very helpful for walls that get a lot of sun during the summer months in places such as Florida. It’s also a great way to cover any lead based paint!
Finally, you will want to insulate the attic to an R value of 30. This is the most important place to insulate, since this will stop rising heat from being lost. Again, a roll insulation can be used here by simply laying the product between the ceiling joists on the floor of the attic.
If the attic is floored you must either cut holes and blow in the insulation or remove and replace the flooring material. And if it is at all possible, also look into the new films that are available for an attic. They help bounce heat back out of the attic. Some of these films boast that they can save a home owner as much as 30% on heating and cooling costs.
Good luck ! You will not believe the difference that insulation will make!