Originally Posted by jayrod
I want to completely recess them in an area that will have virtually no airflow or circulation.
You can still get heat transfer by conduction and radiation, if not by convection.
In theory, 20w or 2w or 0.2w with no way to dissipate that power input will result in an unlimited temp. rise above ambient temperature.
Practically, you'd have to measure the temp. rise in your installation. You can get some idea by wrapping the fixture in insulation and waiting 10 or 15 minutes for the fixture temperature to stabilize. Knowing the R-value of the insulation makes it an easy calculation.
Wood chars at 120°C. T.C. Forensic: Article 10 - PHYSICAL CONSTANTS FOR INVESTIGATORS
But I probably still wouldn't do it, because I can't foresee every possible thing that can go wrong with an installation like this.