These office buildings are part of a long-term ongoing building project whereby each new building is used to test one innovation in energy-efficient construction. Mercator I was used to research a low-energy, all-glass facade. Taking the climate facade principle a step further, the inner leaf is of semi-transparent canvas that can be rolled up. Mercator II proceeds from the principle that in offices energy is used more for cooling than for heating. In a reversal of current practice, the south facade of Mercator II is blankwalled and the north facade fully glazed to prevent the sun from heating the building unduly.