  Consumers wish to choose sustainable accommodation for their travels, and in
the case of corporations, may be required to do so. Yet accommodation
marketplaces provide no meaningful capability for sustainable choice: typically
CO2 estimates are provided that are identical for all accommodation of the same
type across an entire country. We propose a decision support system that
enables real choice of sustainable accommodation. We develop a data-driven
address-specific metric called EcoGrade, which integrates government approved
datasets and uses interpolation where data is sparse. We validate the metric on
10,000 UK addresses in 10 cities, showing the match of our interpolations to
reality is statistically significant. We show how the metric has been embedded
into a decision support system for a global accommodation marketplace and
tested by real users over several months with positive user feedback. In the
EU, forty percent of final energy consumption is from buildings. We need to
encourage all building owners to make their accommodation more efficient. The
rental sector is one area where change can occur rapidly, as rented
accommodation is renovated frequently. We anticipate our decision support
system using EcoGrade will encourage this positive change.
