RESTORATIVE SpAcE - the International Academy of Design and ...

Post-occupancy Evaluation
interior luminance and daylighting through
the use of digital photography and photo
evaluation via a false-colour luminosity
rendering analysis. This provides a metric
for documenting the distribution patterns of
associated glare and brightness for each of
the five office environments.
For the five offices we evaluated,
occupants were between 0-15 feet of a
window and had substantial views and an
average daylight factor of 3 percent in the
deepest area of the office space further
away from the perimeter side windows
Occupants reported high-level of
satisfaction with views outside windows
(Figure 9), with higher levels of satisfaction
for occupants situated within 0-10 feet
away from the windows. Occupants located
more than 10 feet away from the perimeter
windows were generally less satisfied with
their views. More occupants who reported
higher levels of satisfaction with their
views were occupying north- and southfacing
offices. This might be in part due to
high levels of luminance and glare index
perceived by the occupants on the east and
west oriented offices rather than due to the
content of the view since they were mostly
of equal complexity.
Thirty five percent of the surveyed occupants
were generally comfortable with the
lighting conditions in their offices, with 15
percent reporting being comfortable only a
few times a year. The low level of satisfaction
with the lighting system was mostly due to
glare from windows, which was one of the
most associated complaints reported followed
by the inconsistency in the amount
of daylight. Occupants of the East and West
offices reported glare conditions to be the
worst compared to those on the North and
South. Occupants reported a number of
SBS symptoms related to their experience
in the building: although not severe in frequency,
visually-related SBS symptoms and
headaches are however among the highest
in frequency (Figure 10).
Each set of photos was analysed by the
using an image analysis and raster mapping
procedure to create both a High Dynamic
Range (HDR) photo, and a false-colour
luminance map. At the same time, the plan
and section for each of the rooms was
analysed to determine the field of vision of
the occupant in the room. This brightness
intensity of the scene was calibrated by
recording the lowest and highest luminance
in the scene corresponding to the occupant’s
field of vision.
As hypothesised, a luminance ratio of 1:5
for the field of vision, or in the 1:10 ratio
within the entire scene, was common for all
testing times for the north-facing office. The
same is true for the morning and afternoon
conditions of the south-facing office. The
east- and west-facing offices consistently
showed huge variations outside these ratios,
with glare perception on several occasions
throughout the day. This indicates that
although these offices meet the daylight
factor recommendation and pass the LEED
8.1 credit test, they fail to provide occupants
with a sufficient daylighting quality to
perform their tasks 19 . With many occupants
preferring to situate their office closer to
the windows, they became subject to visual
discomfort due to unwanted brightness.
The results from our measurements
and image analysis found that, despite an
overcast sky, the range of daylight entering
the offices varied and produced more
distinct lighting conditions in the east, south,
and west offices, predominantly during
the noon data points when the sun was
strongest. Data suggests that the east- and
west-facing offices have more luminance
variations that exceed the 1:3/1:5 rations
within the field of vision for both facades.
This result in poor lighting quality conditions,
reinforced by the occupant choosing to
switch on the electric light in the afternoon
to balance glare from windows. The southfacing
office has a smaller aperture, as well as
external shading devices, which contributed
to lower light level than the other perimeter
offices, but these balanced the daylighting
quality and brightness patterns in the space.
As hypothesised the north-facing offices
provided the most balanced brightness
patterns and was the brightest in terms of
light levels and luminosity. Occupants turned
off their electric light system in their north
offices most of the day (Figure 10).
Biophilic qualities: green roofs pay
dividends
City areas are warmer than suburbs or
rural areas due to less vegetation and
more infrastructure surface coverage that
radiates heat back into the atmosphere,
creating an urban heat island 20 . To mitigate
this, conventional roofing material may
be replaced by a white or reflective cool
roofing material with high solar reflectance
and thermal emittance, or a green roof,
which consists of a layer of vegetation over
a growing medium on top of a synthetic,
waterproof membrane.
The OHSU-CHH building utilises both
green roof and cool roof technology 1,5 . One
of the building’s key green design features
is a 2,100sqm green roof for stormwater
management, rainwater harvesting and
temperature moderation (Figure 11). Given
the growth of LEED-certified building
design, the effectiveness of such features is
under tight scrutiny 20,21 . For this section of
the study, we compared the performance
of the green roof and cool-roof surface
materials’ heat-reduction capacity.
To investigate the effectiveness of
both systems, we set-up a 2x2 quasiexperimental
research design to study the
performance of both roofs in a southern
verses a northern orientation, as well as
in an accessible verses non-accessible roof
conditions so as to vary the variables studied
between the two systems. The variety of
roof systems employed at the CHH building
Figure 10: False-colour rendering luminous distribution images of five offices compared at different times of day
www.worldhealthdesign.com WORLD HEALTH DESIGN | January 2012 65