Halo® is The Advanced Rigid Insulation Envelope - it's the insulating system perfectly designed for specific applications. Halo is powered by Neopor® GPS (Graphite Polystyrene) by BASF® - the new standard in thermal insulation. Halo's GPS foam core offers best-in-class R-value and is Green Guard® Certified for superior indoor air quality. Halo® Subterra® is perfectly designed for Below-Ground Applications. We call it the "Advanced Below-Ground Rigid Insulation". Halo Subterra is jobsite tough because it's protected on both sides by an incredibly tough woven laminate. Plus, Subterra offers a built-in water-resistant barrier (when taped).