Interior Door Design

Hi I'm a furniture design student and I'm currently investigating interior doors inview to create a stylish and innovative product to fill the niche in the retro-fit market. I'm looking to concentrate primarily on the construction and I'm finding products which will improve the heat and acoustic insulation of the cavity.

Does any one have any suggestions or any problems they have encountered with their existing interior doors/doors you have recently bought? What would you improve if you could or what impressed you? Any comments would be gratefully recieved!

Thanks!

It's pointless trying to improve thermal properties, as rooms should be, and generally are, equal in temperature, and there is no need to insulate.

Acoustically, there may be a reason to improve this, but it will have to be done as part of a door set and not just the door - otherwise sound will get through the gaps between the door and frame.

I don't know what niche you are hoping to fill though