HVAC & Mechanicals
Be economical, direct, and don't get kinky.
But some buckets are more relative
New energy codes are coming (very) soon; many states are jumping straight to the most aggressive one
In a tight, energy efficient house, the HVAC system can make or break you
You can control the bath fan and the light from the switch, automate with motion and sensor controls, or you can mix and match methods. You can even tinker at the switch