And you plan to stay in it well past your "golden years", consider putting in an elevator shaft. It costs little to nothing to put the space in during design and construction, but enormous cost later. You don't have to put the elevator and mechical stuff in until you need it. You can potentially use the space for storage room(s) until you need to install. We thought our neighbors were crazy when they suggested it to us, but as we think about bringing parents into our house when they age, this may help make things easier on all of us.

We also unstalled geothermal heating/cooling. My gas/electric bills are essentially the same as our former house which was about half the size. Again, long term ROI in this investment but less maintenance costs than typical HVAC, too.