In homes or buildings with frame construction over a basement or crawlspace, the floors are usually constructed with framing members called joists, which rest on the foundation sill and support the floor above. The outside ends of these joists, and the space between them, are covered with a band joist (also called rim joist or "header"). This band joist is usually the same size as the floor joists, and runs around the entire perimeter of the building. An uninsulated band joist can account for a significant portion of a building's heat loss, as the only thing separating inside from outside is 5 cm (2 inches) of wood and the siding material covering it. The heat loss through an uninsulated band joist increases when the basement is kept warmer, or contains heating or water heating equipment (as in your situation). Insulating a band joist is an easy way to improve a building's energy efficiency. Unlike finished walls, the band joist is usually readily accessible from the basement (unless the basement has a finished ceiling). The amount of materials needed is minimal due to the relatively small area involved; there are no expensive or specialized tools required; and the skills required are very basic. As a result, the cost of insulating a band joist is relatively low compared with the potential energy savings. Materials: Band joists are usually insulated with either fiberglass batts or rigid foam insulating board. If using fiberglass, use R-12 (minimum) on structures with two-by-four sill plates, and R-20 with 15 cm (six inch) wide sill plates. If the fiberglass has a facing or vapour retarder, be sure that the insulation is installed with the vapour retarder towards the heated space. If using rigid foam board insulation, 7.5 to 12.5 cm (three to five inches) of thickness should be sufficient, depending on the R-value per inch of the material. Foam board insulation materials will generally range from R-3 to R-7 per inch, with the R-value indicated on either the packaging or the insulation board itself. Use enough to achieve a total R-value of 12 to 20. Other than the insulation itself, the only materials needed are some type of fasteners to hold the insulation in place. If using fiberglass, the insulation can be fastened with wire fasteners called "tiger claws". If using foam board, the insulation can be "friction fit" in place if it is measured and cut carefully. Although more expensive than fiberglass, rigid foam board can be a preferred choice due to its ease of installation. Installation Tips: Before installing the insulation, be sure to check any air leakage at the foundation sill joint, and caulk or seal this joint as needed. On the two sides where the floor joists are perpendicular to the band joist, cut the insulation material to a snug fit, and gently push it into place between the floor joists. Be sure that it fits snugly against the band joist, without being compressed (compressing insulation reduces effectiveness). On the sides where the floor joists are parallel to the band joist, cut longer pieces of insulation (sections of 1.2 metres (four feet) or less are easiest to work with). If using fiberglass, the insulation can be held in place with staples (if faced), "tiger claws," thin wire, or fishing line crisscrossed around tacks or nails at one-foot intervals. If using rigid foam board, the insulation can be "friction fit" or glued directly to the band joist for additional holding power. Be sure to fit the insulation snugly around any pipes, wires, or other penetrations through the band joist. Any penetrations should be caulked or otherwise sealed prior to installing the insulation. If any water or heating pipes run along the band joist area, be sure that the insulation is fitted between the band joist and pipes, with the pipes on the warm side of the insulation. If rigid foam board is used, caulking can be applied to the joint between the foam board and adjacent wood or concrete after the insulation is in place, to obtain the desired air seal. Cost/Savings Information: In most cases, the cost of insulating a band joist is minimal. The primary factors affecting the potential savings are the average temperature in the basement and typical winter outdoor temperatures. The greater the difference between warm basement temperatures and cold outdoor temperatures, the greater the heat loss through the band joist, and the greater the potential savings.
Yes, it matters very much. Uncovered earth will radiate moisture vapor that will shorten the life of the insulation and cause the wood to decay quicker on the underside of your house. It will also increase your utility costs. Get some 6 mil black contractors polyethylene from The Home Depot and have it placed under your crawl space. It is one of the least costly, highest benefit things you could do.
Depending on what type of floor joists you have there could be several answers. I will presume that they are 2x8 or 2x10. A system I have used is to strap the bottom side of your joists with 2x4 the opposite direction of your joists. Make sure you insulate the rim joist. I would then line the bottom of the strapping (over the strapping not between) with a good quality Styrofoam. Caulk the joints and make this as air tight as possible. This should be sheathed with thin plywood to hold it in place. Now we have an area that you can pump heat into and will distribute around the floor joists, this may take more than one run depending on the size of the floor. A register cut into the floor at the opposite side of the room will cause the warm air to find a way out of the floor area heating everything in between. Be careful the humidity in the crawl is under control and there is no water coming in.
It is mainly to keep it close to the ground. You'll only require enough to do so.
If you ventilate the crawl space, it will make your floors even colder. The only reason to ventilate the crawl space is if there is a moisture problem. Adding rigid insulation under the joists will help, but you could also glue the rigid insulation to the outside walls to the crawl space to help as well.
The best way to insulate a crawl space is to insulate the walls with a vinyl faced fiberglass insulation. It is very difficult to get a good thermal seal with the batts due to duct work & plumbing in the floor.
I would use both the R-13 fiberglass roll insulation along with the reflective insulation barrier stapled to the bottom of the floor joists. We also have a 3" vinyl faced insulation that we use to insulate the exterior walls of the crawl spaces.
Spray foam it. No need for any wire or rods or anything. Foam is the only insulation that will pay for itself.
You can use an air barrier material that breathes, such as Type, however, this should not be necessary if the crawl space is properly ventilated and you have installed a dam-proofing layer such as 6 mil poly over the ground. Basically, a crawl space works the same way as an attic, except upside down. Cover the poly with some crushed rock or sand to protect it.
Usually making sure all the dirt on the outside slopes away from the house and that your downspouts drain away from the house. Flooding from a city pipe is the cities responsibility.