As environmental issues such as global warming have come into focus, Keio Plaza Hotel has been undertaking various initiatives both inside and outside the hotel since 1991 to help preserve the global environment. One such initiative was the large-scale rooftop greening project on the 7th floor of the Main Tower in 2008.
Rooftop greening, which has garnered attention as an effective measure against the heat island effect in large cities, involves placing lightweight soil and plants on a waterproofed rooftop. The plants' transpiration is expected to help lower the surrounding temperature. At Keio Plaza Hotel, the 7th-floor rooftop, which spans approximately 3,000 square meters, was newly designed to include an outdoor pool area that is popular every summer, a traditional Japanese rock garden (Karesansui) with seasonal trees, and a rooftop garden with greenery. The plants used in the greening section were evergreen Liriope, which are strong enough to withstand the high-rise building winds, and were planted in a modern striped design, achieving both environmental consideration and a beautiful landscape.
The heat island effect suppression by this rooftop greening is said to be equivalent to "an average of 145,000 kcal per hour, or the continuous operation of 75 room air conditioners (for an 8-tatami mat room) for 3 months from July to September." Keio Plaza Hotel's rooftop greening contributes to the environment with its beautiful and comfortable greenery. This oasis-like space floating amidst the skyscrapers of Nishi-Shinjuku is a symbol of the hotel's ecological efforts, which have included initiatives such as waste separation and recycling, energy conservation, and wastewater treatment.
