Floor joist and crawl-space-insulationFloor joist and crawl-space-insulation are important for conserving a lot of energy. Many homes are built without insulation between the floor joists and the floors are cold. Fiberglass insulation was a nasty, itchy product. Today, it’s not bad. There are several methods of insulating your house, but we will stick with the most economical and the easiest. There are a few considerations to make before you get started. First of all, you should consider the local climate. Insulation comes in many forms, but the least expensive is the fiberglass rolls, so I’ll only cover that kind.
Batted insulation comes in different widths and lengths. The two standard widths for wall studs are 16” on center and 24” on center. Insulation is made to fit snuggly into the walls, so both widths are available almost anywhere. The money spent on insulation is always money well spent. Three decades ago, the standard wall thicknesses were the width of a 2x4 stud. We know better now, so most walls are made with 2x6’s instead. This allows more insulation which is a good thing in both the summer and the winter. Insulation is measured by its R-value. The higher the R-value, the better, and usually the thicker the insulation. Here are some examples of R-values and insulation thicknesses. The climate map is a general guideline. Local codes will be slightly more demanding.
Most codes have a minimum of R-11 for the walls, but if you have 2x6 walls, you will be better off with R-19. It will make a lot of difference in temperature extremes. You can see the R-values according to board thickness in the graph in the illustration below. Some insulation bats have a small flap on the edge to staple so it stays in place. Other rolls might need to be held in place with plastic.
It’s really important to insulate the floors as shown in the drawing below. Some might not feel it necessary to insulate the floors, but it makes a big difference in heating and cooling a home. The crawl-space-insulation is the same as floor joist insulation unless you want extra insulation, then you'll need to hold the insulation on by stretching plastic over it. Insulating a Gambrel roof is different than a normal rafter roof because you will need to roll R-30 or R-38 into the rafters as shown below.
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