There are high energy efficiency standards in construction, and then there are extremely high energy-efficiency standards. The German Passivhaus (passive house) construction minimizes heating requirements by implementing superinsulation techniques and ensuring near air-tight construction.
The Passivhaus standard includes the following requirements:
A building must have a maximum annual heating energy use of 15 kWh per square meter (or 4,755 Btu per square foot) as well as an equivalent cooling load (1.39 kWh per square foot, since you’re most likely using electricity to cool).
A building must have a maximum source energy use for all purposes of 120 kWh per square meter (11.1 kWh per square foot) per year.
A building must have an infiltration rate no greater than 0.60 AC/H @ 50 Pascals.
To those of us in the construction defect community, a tighter house means more potential for mold. And “mold” is a four-letter word.