Consider a new 5500 sf custom house that had the below floor plan printed on its street side signage to show how many rooms and spaces this home offers a potential buyer.

The land cost and market history suggest a magic number of how many square feet needs to be built. The builder and his designer fills this 'magic sf' with rooms that will cost $100 to $150/sf to build, and 5 kWhr/sf/year to heat, cool, and light.  

Buying a House-Investment or a Home?
Is that big house with all those seldom used rooms still on target for today's market? Are today's buyers still looking for a big-sf-house investment to flip in two years? Or are more of them looking instead for a smarter home to grow with, live with, and stay with? 

Build in some Green Magic
The market has swung to buyers seeking smarter designs with 'green magic'. If the above builder redesigned this 5500 sf big home to work well with 40% less sf, he could save $330,000 in construction costs and save the buyer up to $2500 annually in utiliites. How much 'green magic' such as super insulation, window & roofing upgrades, and solar PVs would 1/3 of that $330,000+ buy? How much more home would $200+/month less utilities justify for a buyer?