Indeed! I also found it let me indulge in a secondary passion of mine which is fuel efficiency. For example, when I'm building it myself I can make the walls ludicrously thick and insulated to the point where it stays a relatively moderate temp inside even without climate control. I built a shed to use as a luxury dog house, and it was tight enough that a single small space heater could keep it quite pleasant in the winter (when outside temps would be a low of around 12 deg F and high around 28 deg F).

Material costs were a little ridiculous, but since I'm only building for myself that wasn't a huge issue :-)

tight is not the goal - a home needs to breath

This is accomplished in new builds with intentional ventilation. My above-garage ADU accomplishes this with a schedule on the bathroom fan and a make-up air intake in the utility closet. A more expensive (and more efficient) route would be to install an HRV or ERV.

As an energy consultant friend explained to me: You want to control the ventilation rate, rather than relying on whatever you get accidentally (which may not be enough, especially on calm days).