Both in absolute and in relative terms our environmental performance reflected in our net carbon footprint improved by around 7%. The improvements were mainly caused by a higher use of green energy instead of grey energy and a lower amount of business car travel. Also in 2015 our entire travel kilometers cause the greater part of our CO2 emission.
The year 2015 is the second time we composed a joint Deerns Multiplier for Deerns Group. Like last year we managed to increase this sustainability parameter with another 25%, which means a Multiplier of 1,249.
Our most effective way to accelerate sustainability still is CO2 reduction in our projects by our advanced and innovative energy concepts. The Deerns Multiplier shows our achievements in comparison to our own environmental impact. In 2015 the CO2 savings in our most sustainable projects over the entire lifespan amounted to 1249 times our own annual CO2 emissions caused by our own business operations.
We notice that the contribution of every single National Office has increased, but that the most striking increase has come from our UK office due to the large innovative datacenters. This result shows that we are well on track to our firm-wide goal for 2017 to bring our Multiplier at the level of 1500.