3. 8 L [ 1 gallon U.S.] water per flush,
faucets with 14-second shut-off
timer), and currently consumes 65%
less tap water than that of an ordinary
office building in Japan. In addition,
100% of the non-tap water necessary for a biofilm process is provided using treated wastewater and
YKK understands the importance of
being a good corporate citizen and
integrating themselves with the local
community. Examples of its commu-
nity engagement include: using out-
door plants (with signage) on its site
that have been present in its neighbor-
hood since the Edo period (approxi-
mately 1615 to 1868); promoting
buildings) this 11-year payback
period would be less than two years.
The actual reduction in CO2 emissions is 22. 6 kg-CO2/m2 ( 4.64 lb/ft2)
or 32% below the baseline (CO2
emission factor in Tokyo, electricity: 0.496 kg-CO2/k Wh
[ 1. 1 lb-CO2/kWh]; natural gas:
2. 23 kg-CO2/k Wh [ 4. 9 lb-CO2/k Wh];
and tap water: 3.129 kg-CO2/m3
[0.19534 lb/ft3]). This building also
incorporated high-efficiency water-saving equipment (water closets:
ABOVE The ninth floor is the communication cafeteria for the worker, and is also
available for meeting space.
BELOW Green roof with sweet potato
leaves can cool the air around the air-conditioning unit on the rooftop.
A project’s success is a direct reflection of the strength of the owner’s
goals. With nearly 30% of Japan’s
energy supply shut down just weeks
after the earthquake and tsunami of
2011, the focus on radical energy
efficiency and a 100-year design
solution became critical objectives.
Lessons in achieving thermal comfort
from CFD simulation to full-scale
mock-up testing with 150 participants
and subsequent post-occupancy evaluation helped achieve a low-energy
thermal comfort success.
Design lessons around 100-year resiliency in earthquake resistance as well
as exterior mechanical duct access and
architectural shading of the west-facing
façade using an elegant aluminum
screen (or sudare, in Japanese), while
maintaining views and daylight all contributed to the high-performance results.
farm-to-table food using their rooftop
garden; and offering local handicraft
manufacturers opportunities to hold
workshops and exhibition events using
the area around the building entrance.
Based on the latest data from Tokyo
Metropolitan Government, YKK80
energy performance is in the top 1%
of the 465 buildings sampled.
Focusing on the initial project goals
of energy-savings, comfort, health,
seismic safety, and cost-effectiveness
through life-cycle design, the YKK80
building has clearly met, and even
exceeded these goals—providing a
new benchmark for high performance
office buildings in Japan. •
ABOUT THE AUTHORS
Susumu Horikawa, P.Eng., is a executive
officer, principal, mechanical and electrical
engineering division, Kitaro Mizuide, Ph.D.,
P.Eng., is a general manager of the mechanical and electrical engineering division, and
Taro Hongo is a mechanical engineer at
NIKKEN SEKKEI, Japan.