"I could make more money doing a conventional building on the site, and we always have that option," he said.

"But I've worked 30 years to be in a position to not have to do the conventional building."

On average, however, passive houses are still up to 14% more expensive upfront than conventional buildings.

In a conventional building this presents a problem as it leads to the need for increased air conditioning.

And the ballroom would be difficult to duplicate in a renovation of a more conventional building.

These buildings make use of heat energy that conventional buildings may exhaust outside.

This is quite an accomplishment: you try coming up with a scheme to give everyone a corner office in a conventional building.

The dome was cheaper to cool and heat than a conventional building.

There was not a single conventional box-shaped building in sight.

However, new construction, whether green or conventional building, will in general be of higher quality, more efficient and healthier than older buildings.