How much gap can exist between butted insulation boards?

The allowable gap between butted insulation boards is indeed a critical consideration in roofing applications, particularly for maintaining thermal efficiency and preventing airflow issues. A gap of 1/4 inch is the recommended maximum because it allows for some expansion and contraction that can occur due to temperature fluctuations without compromising the insulation’s overall effectiveness.

Having a small gap like 1/4 inch helps to mitigate issues like moisture accumulation and promotes proper ventilation. Larger gaps, such as those of 1/2 inch or 1 inch, could lead to thermal bridging where uninsulated areas reduce the overall performance of the insulation, as well as potentially allowing paths for air and moisture that can diminish the integrity of the roofing system.

In applications where insulation is critical, maintaining consistent coverage without excessive gaps is essential to ensure efficient energy performance. No gap at all is not practical in real-world scenarios, as slight movements and material expansion need to be accommodated. Hence, a 1/4 inch gap is the optimal choice for balancing practicality and performance in roofing insulation installations.