Poor heating - Incomplete/incorrect iFlow, Navian?

[iFlower]

I have a Navian boiler with an iFlow air system that provides air around the house via high velocity conduit. It's just over a 1 year old property and I just moved in and found the heating suboptimal.

I have had a plumber indicate the system is designed and installed incorrectly, which the builder disputes. I am filing for a warranty claim but curious if I could get some internet stranger bias or advice one way or another.
Issues:
Heating in most rooms is poor, room does not reach temperature set point on thermostat of 23c
Boiler/heating comes on and off frequently (every 20-30 mins)
No return airflow from upper level into boiler/hvac, possibly causing balancing/pressure issues
There's open ducting going from the mech room directly outside
Boiler intake not connecting to fresh air inlet

The plumber claims
the high velocity ductwork is incorrectly designed and needs to be re-done
there's leaking or missing ducts in crawlspace
gas line code violations
incomplete iFlow setup
no recirculation
pipes un-attached (pressure relief valve?)
incorrect material used (90' ptex connectors?)

Can anyone provide their opinion based on the photos and confirm the plumbers concerns?
Thanks
Photos of setup

Plumbing/heating

22 new items added to shared album

photos.app.goo.gl

 

[gmartine]

I'm not qualified to comment on the code violations but even I can tell the twin flue is incomplete and the pipe and duct work is extremely shoddy. I wouldn't waste any more time, it's clearly a very poor installation probably done by the builder. Report it to the trade body in your state, get it corrected and sue.

 

[oz-plumber]

Horizontal auto-airvents says it all!

Send that pic to the manufacturers or suppliers, guaranteed they will look at that and instantly tell you that the issue is an installation problem not a equipment problem.

Good luck getting it sorted with the builder - I won't hold my breathe for you.

As for the air inlet to the boiler - on par with the horizontal auto-airvent.

As for the rest of the pics you posted - Lawyer Up.