See section R401.2.1 Tropical Zone
Essentially, if you don't have air conditioning, no insulation in walls or floors required, and reduced ceiling requirements.
I think Hawaii is actually using the 2015 IECC with amendments.
https://energy.hawaii.gov/wp-content/upl...dments.pdf
The above changes up the ceiling insulation requirement a bit, with a higher requirement (R-19) if you don't have a reflective "cool roof", and a lower requirement (R-13) if you do.
A exposed beam ceiling should still work. One layer of 2" foam board on the roof plus a white (reflective) steel roof surface would meet the requirements of the code.
When I contacted the code people about details of insulation requirements and options for a shall we say, unconventional dwelling, they sent me a link to this:
https://energy.hawaii.gov/wp-content/upl...cy2004.pdf
Yeah I know it says commercial, but I was told you can use the commercial system of passing requirements. The advantage of this system, if applicable, is that it works in a radiant barrier as a option to reduce the R-value requirement. In some cases, a white roof combined with a radiant barrier removes the insulation requirement entirely.
They have several combinations of roof surface, insulation, and radiant barriers that are acceptable. They have a calculated value that combines the three things (insulation, reflective surface, radiant barrier) to give you a single number to pass. They call this the RHGP (roof heat gain factor). See section 6.