I am a strong proponent of planning ahead for successful functional performance testing. This is why commissioning starts in the design phase, continues through construction, and culminates (doesn’t start) with functional performance testing when the systems are installed, started up, balanced, integrated, and fully operational.
When the entire project team is engaged in a sincere and meaningful way in the commissioning planning, coordination, and integration process, we have seen testing go very smoothly and result in very few issues that need to be resolved at the end of construction. On the other hand, if the project team, or even just one or two key members of the team, do not take the commissioning planning process seriously and/or choose not to participate, the number of issues discovered during testing increases substantially.