Gas Tankless Water Heater

[RTK]

I'd like to install a tankless water (NG) heater on the outside of my house. What are the constraints? I think I have a good spot for it but how far away from windows and doors should it be? What does the IRC say about it and where? I've combed through mine but I couldn't find anything about the placement of a tankless water heater. I have the 2003 version.

[jnaas2]

WHY would you install it on the outside???????