State-of-the-Art Insulation Good insulation is the most critical requirement for a great performing solar oven. The Sport insulation has an excellent R 6.5 value. It is reinforced with glass fibers to protect it from heat degradation and help it resist crushing. The Sport insulation material will not absorb water. It is composed of thousands of tiny, sealed, air holes that water cannot penetrate. This is a key design feature because moisture is always present in solar cooking as steam and humidity.