How should double layers of rigid board insulation be installed?

Installing double layers of rigid board insulation with the layers vertically staggered and offset is essential for enhancing the insulation's overall effectiveness and minimizing thermal bridging. When the seams of the top layer are offset from the seams of the bottom layer, it significantly reduces the likelihood of heat loss through the seams where the boards meet. This technique creates a more continuous thermal barrier, as it prevents gaps that could allow for air infiltration and thus improves energy efficiency in the building.

In contrast, aligning the seams vertically would not provide the same level of insulation effectiveness due to potential alignment of the gaps, which can lead to thermal bridging. Stacking the boards horizontally would similarly fail to provide the necessary offset, leaving areas vulnerable to heat loss at the seams. Using only a single layer would not deliver adequate insulation value as well. Therefore, the configuration of staggering the seams is established as best practice in the installation of double layers of rigid board insulation.