(JBED) - Summer 2006 - The Whole Building Design Guide

1. COMMERCIALLY AVAILABLE
SOLUTIONS: AUTOMATED BLINDS
AND SHADES
Blinds and shades are used in most
U.S. buildings today but unlike European
experience, virtually none are motorized
and few are externally mounted. The assumption
is that that these shading systems
are available for occupants to control
localized glare and solar gain but they
are not relied on to control building envelope
performance. Accordingly, most energy
standards do not provide any credits
for systems that rely on occupant action
since the response is unknown and uncertain.
Furthermore, engineers will generally
size HVAC systems assuming worst case
operating procedures—e.g. that the shading
systems are not operated as planned.
Large glazed areas, even if heavily tinted
and reflective, may be insufficient to fully
control glare on sunny days.
the U.S., nor are systems that further link
the blinds to dimmable lighting controls.
Beginning with “off the shelf” blind and
lighting components, we developed and
tested an integrated, automated blind and
daylighting system in two identical sideby-side
test rooms in a southeast facing
office building in Oakland, CA (Figures 2.1
and 2.2). Large cooling and lighting energy
savings were achieved, peak electrical savings
were measured and the resultant automated
systems were acceptable to occupants
in a limited occupancy study.
Despite the success of the demonstration,
the lack of a cost-effective delivery system
managed by a single vendor or groups of
vendors continues to limit use of such systems.
The project illustrated the market obstacles
from a building owner and manufacturer
perspective in terms of who
serves the “systems integrator” role when
Figures 2.1 and 2.2
Smart controls on the automated blind systems (left photo) keep direct sun out of the space, reducing glare and cooling loads. The same hardware
system with different control strategies (right photo) admits sunlight to offset heating loads but creates excessive glare.
AUTOMATED VENETIAN BLIND AND
INTEGRATED DAYLIGHTING SYSTEMS
Venetian blind systems are widely
specified for control of solar gain and
glare. Because both the optical properties
of the slats and their tilt can be controlled,
they provide a wide range of optical and
solar control. But a number of field studies
have shown that manually operated
blinds are rarely controlled in an optimal
manner. Adding sensors and controls and
automating the blind operation should
permit better control of both energy use
and comfort, assuming that the proper
control strategies can be successfully developed,
implemented and maintained.
These integrated, automated control
systems are not yet commonly available in
12 Journal of Building Enclosure Design
the different system elements are provided
from different vendors. Development
of smart, automated blind systems is
more advanced in Europe and Japan. Although
a growing number of these systems
are now being installed in buildings it
is still difficult to find measured performance
data that clearly demonstrates the
overall energy use of such systems.
AUTOMATED MOTORIZED SHADE SYSTEMS
AND INTEGRATED DAYLIGHTING CONTROLS:
NEW YORK TIMES BUILDING
A second widely used operable shading
system is based on roller shades.
Roller shade systems can utilize different
fabrics encompassing a wide range of solar
optical properties, ranging from blackout
shades to highly transmissive veiling
fabrics. Although mechanically simpler
than blinds, once the fabric is chosen the
shade systems have more limited optical
control than blinds, largely based on their
position between up and down. It is possible
to layer blinds or use optically variable
fabrics but this is not common practice.
An extensive field test program was conducted
using an automated shade system
in conjunction with a high transmittance,
all glass façade for the New York Times
headquarters building, now under construction
in New York City. The 52-storey,
140,000 m 2 building will utilize fixed exterior
shading and fritted glass in some locations
(Figure 3.1) but will require interior
shades for sun control and glare control
and for thermal and visual comfort as well
as energy management.
The exterior of the building utilizes a
transparent floor-to-ceiling, all-glass
façade that encourages openness and
communication with the external world,
consistent with the owner’s dedication to
creating a high quality work environment
for their employees. Low partitions were
used to reinforce the sense of openness
and to let the daylight penetrate deeper
into the space. The cruciform floor plan
(Figure 3.2), with distances from interior
offices to façade of less than 7.6 m, permits
view in three directions from most