Beauty

All homes take a lot of resources to build, and a lot of effort from a lot of people to come into existence. For a house to be truly low impact, that effort and those resources need to last the test of time. To do that, it not only needs to be built well, and function well, it needs to be beautiful.

A building can be super efficient in operation, but if it is not an uplifting, positive space to be in, it will be knocked down as soon as the owners can afford it.  The moral is this - an ugly building will not last long.  So, as well as having spaces that function well for the owners, a green building must also be a beautiful building.  If it is not, eventually the demolishers will come in and instead of being a sustainable outcome, it will be another contribution to the already high churn rate of our housing stock.

Having said all this, it should be noted that sustainable buildings have a lot of things going for them in this regard.  They are generally warmer in winter, & cooler in summer.  They are generally more connected to the outdoors.  They tend to be quieter, and brighter, and healthier.  (See Why Choose a Positive House.)
These are all important traits that contribute to beauty.
But these traits alone are not always enough, and that's where the magic and creativity of the designer comes in.

In the end, the design solution must at least be artful, and where possible, a work of art.  An ugly building is not green.