When is the best time to do duct leakage testing?   

If you're an HVAC Installer,

you'll want to protect yourself with the inspection occurring just after you complete your install.  You can confirm that it's been done correctly and up to current standards before TONS of other people make their way in to do their work.  HVAC systems are one of the first things to go into new construction.  After that you've got electricians, plumbers, drywallers, carpenters, and painters - just to name a few.  Each has their own collection of sharp tools, additional building materials and potential for damaging your mechanical system's relatively delicate pieces.  A drywall knife can easily cut through flexible ducting.  Insulation of any kind being installed in the attic opens the opportunity for feet to accidentally crush duct lines and/or tear them...  In the picture to the left, low voltage lines are laid across a duct line.  This simple mistake can dramatically affect the insulation value of the duct, dramatically restrict airflow through the line, and lead to a multitude of problems down the road including affecting comfort and humidity levels.

If you're a homeowner,