My house was built in 2008 in the state of WA and it looks like they used flex ducts in the crawl and attic. I've noticed when my a/c is on the upstairs doesn't get as cool as the downstairs does also when the heat is on some of the upstairs ( back bed rooms ) doesn't get as warm as master upstairs or downstairs. I've tried the closing off dampers downstairs to force more air upstairs and even had an hvac guy install a air scoop on the furnace to force more air upstairs. Is there anything else "I" can do myself to improve the efficiently and fix this problem? What about wrapping the flex in more insulation or air sealing? I believe it is just the 4.2 but could be wrong. Replacing the flex with hard pipe isn't an option for me right now. Any info will be appreciated.