How should double layers of rigid board insulation be installed in a low-slope roofing system?

When installing double layers of rigid board insulation in a low-slope roofing system, the correct approach is to stagger the joints in each layer. This method is crucial for several reasons.

First, staggering the joints enhances the overall thermal performance of the insulation. When joints align, there can be pathways for heat transfer, potentially leading to thermal bridging, which decreases the insulation’s effectiveness. By offsetting the joints, you create a more continuous thermal barrier, which improves energy efficiency and helps prevent issues like condensation or moisture accumulation in the roof assembly.

Additionally, staggered installation contributes to the structural integrity of the roof system. It minimizes weak points where moisture can penetrate or where the insulation could sag or shift over time. This practice also aligns with building code recommendations and industry standards, which emphasize the importance of proper installation techniques to maximize both insulation performance and roofing longevity.

The other options do not provide the benefits associated with staggered joints and may lead to vulnerabilities in the roofing system.