Gaining Technical Credentials for Residential
by Ken Brenden
Daylighting, well-established as a bona fide green building
option and quantifiable energy saver, is attracting the attention of not
just commercial fenestration manufacturers, researchers, designers and
codes and standards groups, but also that of residential designers, builders
and savvy homebuyers.
Daylighting is an energy-saving measure that reduces the energy demand
for electric lighting and the heat load that electric lighting places
on air conditioning systems. Additionally, studies comparing buildings
with optimized daylighting systems to those without come to the same conclusions:
people simply function better in a daylit environment.
Recognition of all of these positive effects is dawning in official quarters
within proliferating green rating systems, standards and model codes.
While most of these target the commercial sector, recent developments
affecting residential construction are of note.
Fenestration Rating Council (NFRC) has announced
that it may rate windows for daylighting."
New green residential building and remodeling guidelines
in the NGBS adopted early in 2009 emphasize natural lighting. Two points
are awarded for the use of tubular daylighting devices (TDDs) or low-E
insulating glass skylights in rooms without windows (Section 704.2.4).
Section 701.4.4 requires windows, exterior doors, skylights and TDDs to
have NFRC-certified U-factors and solar heat gain coefficients (SHGCs)
in accordance with Energy Star® or equivalent.
Last October, the model code was revised for 2012 to theoretically achieve
energy savings of 30 percent relative to the 2006 version. The approved
changes include all aspects of residential (IECC Chapter 4) construction,
laying a strong foundation for residential efficiency gains. The energy
chapter of the International Residential Code (IRC Chapter 11) was essentially
eliminated and now references the IECC as a single nationwide uniform
energy code for both residential and commercial buildings.
Daylighting Ratings on the Way?
The National Fenestration Rating Council (NFRC) has announced that
it may rate windows for daylighting. A task group was formed at the NFRCís
November 2010 meeting and is scheduled to come back with a recommendation
in early 2011.
The design community is becoming more knowledgeable in the techniques
available for enhancing daylighting.
Devices besides windows serve the goal of bringing diffuse natural light
to interior spaces. Judicious use of skylights introduces daylight throughout
the interior rather than just around the perimeter. The newer TDDs are
increasingly popular for interior areas such as bathrooms, hallways and
kitchens that receive limited daylight and as noted are specifically recommended
for windowless rooms in ANSI/ICC/NAHB-700.
In addition to adding pathways for light to enter, design strategies can
enhance the availability of natural light. For instance, allowing light
to penetrate high into a space through the use of clerestories, light
shelves and vertical baffles projects it deeper into a room, as does sloping
ceilings away from windows and using high-reflectance paint.
Incorporating automatic daylighting controls with these products provides
ideal energy savings by controlling the amount of heat gain based on the
sunís orientation to the building.
While these techniques and their benefits are widely acknowledged, the
growing requirement for daylighting in green standards and codes points
to a need for better defined daylight performance analysis methodology
and quantifiable metrics.
Over time, evaluation techniques, performance metrics and rating systems
will evolve, and will likely feed continued code development. The wise
residential architect and builder, and the alert fenestration product
manufacturer, will get ahead of the curve in quantifying daylighting benefits
for code officials and promoting them to homeowners.
Ken Brenden serves as technical services manager
for the American Architectural Manufacturers Association in Schaumburg,
Ill. He may be reached at firstname.lastname@example.org.
His opinions are solely his own and do not necessarily reflect those of
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