Standard Spacing is 36 Inches
When installing batts or rolls of insulation below a floor or in a ceiling above, using insulation supports is a good idea. The standard suggestion is 36 inches apart. The wire supports should be fastened across the batt of insulation and tightly attached to the support beams.
Steep Roofs Require More
For insulation under an extremely steep roof, 36-inch spacing still may allow sagging of roll insulation. In these cases, experts suggest 24 inches or even closer spacing of insulation supports.
For a standard installation, such as in a crawl space, using supports every 36 inches is fine. Use more supports for steep roofs.