Can we modify UTCI component to do indoor comfort study just to compare indoor and outdoor comfort?
I suggest to do a bit research on UTCI and its capabilities, among others: what it is intended for.
There’s nothing in the software that stops you from using UTCI for indoor studies. But, as Abraham says, there are a number of assumptions built into UTCI that make it inappropriate for indoor comfort studies. For example, the metabolic rate of the human subject is always assumed to be walking with UTCI.
If you want to use a temperature metric that’s applicable to both indoor and outdoor, I recommend just using operative temperature (or possibly standard effective temperature if you need to account for a specific level of clothing or metabolic rate).
I can join, you should look at the boundary parameters. The UTCI also has a minimum speed of 0.5 m/s at 10 m altitude.