They are permanently bonded to the foam core. Adjacent wall panels interlock and attach to the foundation. When enclosed with panels, the house is strong and stable. Urethane foam has a slightly higher insulation value. An R-43 panel has 6.5 inches of urethane.
Additional savings result from their airtightness.
With panels as long as 24 ft. by 8 ft. tall, a typical house wall has few joints where air can leak into the home. This also makes the homes very quiet and clean inside. With a fresh air ventilation system, these are ideal for allergy sufferers. Constructing a SIPS house is fast for lower labor costs. A 2x4 stud is attached horizontally to the foundation.