Thank you everyone for all your help and advice! Yes, we live in an inland part of Southern Australia that is very chilly in winter and exceedingly hot in summer. So efficiency is a very important part of our build. From the picture you added Louise, I think a "coffered" ceiling looks like what I would call an "up lift". I'm glad to have a second on that option ;) The picture looked good, and could defiantly be an option over the dining table I think. Thanks jbantick I looked up "scissor trusses" and they look like a great idea as well. I'm just not sure how they would run. From the entry across the dining area (N to S) or across the whole length of the 3 zones E to W ? The middle of the roof line (running E to W) doesn't run in the middle of the living zones (if that make sense) as it stretches across a hall way on the south side. If it ran this way would it look a bit off centre? How did you in vision it? Thanks for your thoughts guys.

You never mentioned your budget that you're willing to spend. You could add a thicker fill backed insulation blanket - 50mm, 75mm or 100mm are the common thicknesses. Steep roof pitch so would need scaffolding, harnesses, etc.. which adds up quickly. Probably still not enough insulation though but probably cheapest option. Insulation under existing timber linings then reline over the top of that as some have suggested. Working at height though so would need scaffold set up again and working overhead is not fun nor easy. You could replace the roof with a sandwich panel roof. Try Versiclad or Kingspan or comparable. They have a polystyrene type of insulation between an outer metal roof sheet and a metal inner sheet. These are heat laminated together. Again different thickness available from 50mm up to 180mm is common. The 180mm has a R rating of 4.7 which is quite good. Again steep pitch, etc., probably need new ridge capping, etc.. Probably most expensive option...... Keep us all posted on your decision though!

Funny how your query has popped up on the Australian version of Houzz, as we are along way from Nebraska. I would want an explanation from the builder why the coffered ceiling needs to drop so far as they look very heavy and oppressive. Probably the sort of detail I might use in a multi-story carpark. Are the dropped sections concealing plumbing from upstairs? Could he build it without any coffers? If there is a choice between 12inch coffers or no coffers I would go with a flat ceiling. A new home is a lot of money and you need to get it right so I would say 6 inch coffers as displayed in the model home, or walk away. See if he changes his tune... Best of luck Dr Retro of Dr Retro House Calls.

I would prefer to see both ceilings matched with shiplap, to help tie the space, we all tend to look up. This would also mean that the wall between both rooms can be removed and therefore make the room appear bigger, as the height of the ceilings in each room will make them appear smaller if the wall isn't removed