Enhancing Sustainability:
Choosing green products provides quicker payback from improved efficiencies
Walt Lutzke,
Posted
04/01/2010
Architects
are discovering that several feature of architectural aluminum
building products can be combined to enhance the overall
sustainability of metal building projects today, and for years to
come. Although some of these products have slightly higher initial
cost than their more common counterparts, the payback from improved
efficiencies is seen in a relatively short time. These "green"
products also help building owners attract potential tenants and
buyers.
Solar Control
One important factor architects consider in the initial building
design is the window-to-wall ratio, or the total area of a façade
which is comprised of vision glass and framing. The climate
surrounding the project location will influence the optimum ratio
for the building.
In cold weather locations, like the Great Lakes area, heating
energy use increases with window area and decreases because of
daylighting advantages. The target range for WWR is 0.15 to 0.30
varying by the orientation of the window.
In warmer climates, like the Gulf Coast, architects strive to
balance increased cooling cost with larger windows versus the
decreased need for electric lighting. WWR ranges between 0.30
and0.45 are desirable within this region.
Accessories for glass and aluminum framing systems, like sun shades
and light shelves, contribute toward the reduction of electrical
energy use. Furthermore, these may contribute to buildings seeking
to meet green building rating systems' criteria such as U.S. Green
Building Council's LEED program.
Sun shades function like a permanent exterior awning, but are
designed to withstand the elements year-around. They shade the
glass area underneath the unit and block direct sunlight's infrared
radiation, or solar heat gain, from unnecessarily warming the
inside of the building during peak summer months. As the sun's
position lowers during the winter months, more sunlight enters the
building, which helps reduce heating costs/energy use. Many
variations in size, shape and color are available.
Light shelves are internal fixtures mounted on glass walls above
occupied areas. They catch the free, abundant, sunlight on the
building perimeter and redirect it to areas normally lit by
electric lighting. Energy efficiencies are gained with automatic
electric lighting controls. This diffused, natural light not only
reduces electric energy use, but also contributes to occupant
comfort and well-being.
Daylighting
Within the 2009 LEED Green Rating System's Indoor Environmental
Quality category, Daylight and Views' credits are available for
incorporating the use of natural lighting in new
construction.
IEQ 8.1 offers one point for lighting 75 percentof interior spaces
using sunlight. Schools may earn up to two additional points if 90
percent of classroom spaces achieve specified daylighting
levels.
IEQ 8.2 is one additional point for increased daylighting to 90
percent of interior spaces.
Another potential point is available for Thermal Comfort (IEQ 7.1).
This credit is earned by providing a comfortable thermal
environment that supports the productivity and well-being of
building occupants.
LEED credits in the Energy and Atmosphere category also are
possible through Optimize Energy Performance (EA 1), up to 19
points for new construction projects. These points achieve
increasing levels of energy performance above the baseline in the
prerequisite standard to reduce environmental and economic impacts
associated with excessive energy use.
Recycled
Content
Using high-content, recycled, aluminum extrusions for framing of
vision glass areas is an easy and cost effective way to boost
credits for LEED Materials and Resources category, while providing
for thermal improvement at the same time. Recycled, aluminum,
extruded systems are available from many suppliers and in as many
variations.
LEED MR 4 allows one point for a total recycled content of 10
percent, and awards an additional point for a total recycled
content of 20 percent. Total recycled content refers to all
reclaimed building product materials used on the project from the
roofing overhead to the concrete foundations and site-work below.
All of the post-consumer and one half of the pre-consumer content
can be counted.
The recycled content value of a material assembly is determined by
its weight compared to the total building materials' weight. The
recycled fraction of the assembly is then multiplied by the cost of
assembly to determine the recycled content value.
Key points to consider in pursuing LEED MR points
include:
• Post-consumer content-Qualifying, aluminum material
includes that which is diverted from landfills after their previous
lifecycle. This content is made from such items as beverage cans,
home siding and automotive wheels. Rigorous selection of recycled
material during the "smelting" stage is critical to the output
quality of recycled aluminum.
• Pre-consumer content-Qualifying, aluminum material
includes that which is reclaimed from manufacturing production
processes. It is more abundant than its post-consumer
counterpart.Please note that reusing material reclaimed from the
same process in which it was generated does not contribute toward
its recycled content. Examples are glass culls reused in the making
of new glass, and metal scrap reused for new product within same
facility.
• Prime aluminum-Primary billet aluminum generally is
included in the overall recipe of recycled aluminum, as well.
Available combinations of these three components vary per supplier.
Higher post-consumer content contributes more toward MR 4. Pre- and
post-consumer content totaling 100 percent is possible, but
typically requires special ordering.
Finishes
Architects also can specify new anodizing processes for aluminum
that reduce the amount of waste by-product and produce high-quality
finishes when used with recycled aluminum. The anodizing process
involves multiple baths. The first of these baths is an etching
tank that removes a portion of the aluminum extrusion surface to
clean it before an electrolytic hard-coat is applied. Use of
low-pH, chemical bath for etching only removes five percent of the
surface that higher pH chemicals do. The lower pH bath also works
better with recycled aluminum and produces a more consistent finish
with a lower reflectivity.
Painted finishes for aluminum framing also add an attractive
dimension that can be environmentally sensitive. Whether spray or
powder-coat, responsible paint applicators remove all Volatile
Organic Compounds during the drying process before materials leave
the manufacturing facility. Because the VOCs are removed before
reaching the job site, they do not apply to low-emitting materials
outlined in LEED.
Features of the anodizing or painting of aluminum framing systems
do not contribute directly toward any LEED points; however, they
are generally considered as beneficial aspects of overall,
sustainable design.
Thermal
Performance
Energy efficiency is increasingly seen in specifications and
construction product features. Aluminum framing systems for
storefronts, curtainwalls and entrances offer a variety of thermal
barrier designs with varying degrees of performance. Materials
include simple, rubber insulator pads and gaskets;polyurethane
filled pockets; and high-performance, polyamide glass, fiber
struts.
The U-value provided by these thermal breaks is the measure of
temperature transmitted or conducted through glass and aluminum
framing member.The lower the number, the less temperature is
transmitted to the building's interior. A good range of performance
is 0.43 to 0.48 U-value.
Condensation Resistance Factor is another industry measurement to
help reduce the occurrence of frost on interior aluminum frame
surfaces. Sub-zero outside temperatures combined with high winds
versus comfortable indoor conditions with high temperatures and
humidity levels require framing systems that stop the transfer of
cold. For CRF, the higher the number is, the higher the product's
resistance to condensation. Look for ratings between 64 and 69
CRF.
Glass selection plays an important role in the overall performance
of the framing system's U-value.Glass is a natural, thermal
insulator and performs better than the aluminum framing system
holding it. Because of the large surface area of glass compared to
the framing system holding it, the glass has a great influence on
the overall performance of the system. This ratio of glass vision
area to the total surface area, including the framing system, is
used in calculating the performance of U-values and CRF.
Coated glass products, such as low-E on insulated glass units, help
to block infrared radiation, orSolar Heat Gain from reaching the
building interior. Reduction of this excess heat lessens the need
for air conditioning during the summer months. Allowing more heat
from sunlight reduces the energy required for heating during the
winter months. A balance of these two factors is needed to achieve
the optimum combination.
Features of high-performance glass that provide higher U-values are
focused on the space between insulated panes. Typical insulated
units are made from two, 1/4-inch (6-mm) glass sheets separated by
1/2-inch (13-mm) of air- or gas-filled space. The spacer creating
this half-inch void is sometimes made from metal, which also can
transmit temperature. This spacer can be produced with its own
thermal barrier to reduce the potential for transference of
temperature.The insulated space between glass panes can be filled
with special, rarified gases like Argon, and are inserted at a
negative pressure for increased thermal properties.
LEED credits for the glass and aluminum glazing system have been
identified earlier as Optimize Energy Performance (EA 1), and
Thermal Comfort (IEQ 7.1).
Another aspect of Thermal Comfort involves contributing to LEED
points by allowing occupants' control of their environment through
products like operable windows. Fresh air can be accessed, when
desired, at the discretion of the individual.
Sustainable building features are now more available and more
affordable than ever. Sunlight, temperature, energy use, occupant
comfort, aesthetics, recycling and profitability can be combined
through a little research and planning. Whether preparing for new
construction, or looking for ways to renovate and upgrade an
existing property, the products and practices to assist architects
with success are easily accessible.
Walt Lutzke works for Walker, Mich.-based Tubelite
Inc. Drawing from 28 years in the industry, his experience includes
development and distribution of print and electronic product
information for contract glaziers and architects. Continuing his
professional development, he represents Tubelite's involvement with
the American Institute of Architects, Construction Specifications
Institute and the U.S. Green Building Council. For more
information on Tubelite, visit www.tubeliteinc.com.
www.tubeliteinc.com