Taking the Green Exterior Beyond Energy
Source: Building
Operating Management
An
integrated planning process is the key to a green envelope. By Abigail May
What does “green” mean where a building envelope is concerned? For many
facility executives, “energy efficient” is the first answer that comes to
mind. They’re right: The exterior plays a critical role in determining a
facility’s energy consumption, which is a large part of its overall impact on
the environment.
But energy efficiency is not the whole story. Increasingly, designers who strive
to build green facilities take into account, along with energy efficiency, the
envelope’s impacts on building occupants and on the surrounding environment --
be it rural or urban -- and the overall life-cycle impacts of the materials
involved, including their manufacture, processing and transportation.
There is a lot to be concerned with. And while there are many guidelines and
tools available to help with decision-making, even the most environmentally
savvy designer will tell you that there are relatively few hard and fast
answers.
Green exterior basics
An environmentally sound envelope starts with basic architecture.
“Orientation makes a huge difference,” says Tom Nelson, vice president and
senior project designer with HOK.
An east-west orientation generally will help mitigate energy consumption by
making it easier to minimize western sun exposure -- the most difficult in terms
of solar heat gain and glare. In addition, it may make sense to minimize window
openings on the western side and, instead, to concentrate them on the south side
of the facility, where summer sunlight will be less intense and shading can be
used to control glare.
Floorplan is also important: Narrower floorplates will allow sunlight to
penetrate deeper into the facility, reducing internal lighting requirements and
energy demand.
In addition, explains Bill Browning, principal and founder, Rocky
Mountain Institute’s Green Development Services, “you generally want the
longest facades to be north and south facing. It’s easiest to control the
light coming into them.”
Basic design steps like these constitute what Nelson describes as “passive
strategies.” For facility executives involved in new construction, these are
important strategies to employ when attempting to achieve a green exterior;
compared to more technology-reliant strategies involving building-system and
materials choices, passive strategies are cheap.
“We can do a fair amount of sustainable design without influencing cost,”
says Nelson. “Some of it is just basic architecture and doesn’t cost
anything.”
Specifying for sustainability
When the discussion turns to the specific systems that make up a building’s
skin, technology quickly becomes a major factor in determining environmental
impact. At this point, choices and cost analyses become more complicated. But
the stakes at this stage in the game are high and the decisions important: The
products and systems chosen for the exterior of a facility go a long way toward
determining how green a building will be.
Just how critical a building’s skin is to its environmental impact varies
somewhat with the size and type of building and its intended usage. For example,
in skin-dominated buildings -- often those under 50,000 square feet -- the
energy efficiency of the building’s exterior systems and design are critical,
so considerable effort goes toward adjusting for heat gain or loss. In larger,
load-dominated buildings, the activities inside the facility are often a bigger
factor in its overall energy consumption, so the skin characteristics may be
less meaningful than the building’s internal systems and design. Factors like
these are important to consider when deciding how much of your construction
budget to direct toward greening the exterior.
For all facilities, windows have a major impact on environmental friendliness,
primarily for their energy efficiency effects. The fenestration options
available to today’s specifiers are myriad, and the best choice depends on a
combination of variables, including climate; building type, size and usage; and,
of course, budget. There are, however, some basic guidelines that will hold true
in most applications: Low-e glazing is a baseline rule of thumb for energy
efficiency. Multilayer glazing adds additional efficiency, and coatings with
appropriate spectral performance characteristics should be chosen based on
exposure.
“There are various technologies that can allow you to start controlling heat
and light flux across the envelope,” says Browning. “You can get lots of
heat and light where you want it, but control the infrared.”
Windows also have a profound effect on both energy efficiency and indoor
environmental quality (IEQ) where daylighting is concerned, as effective
fenestration can create a better indoor environment while lowering heating and
cooling demands. Architecture can lend a hand in this area, as well. A building
can be designed to shade windows, allow maximum light penetration, or offer both
shaded windows and full daylight.
Roofs and walls
Roofs also play an important role in the design of a green envelope. “A cool
roof can save you 20 to 30 percent on cooling annually,” says David Gibney,
sustainable design coordinator, HDR.
That translates directly to lower impacts on the environment as a result of
reduced energy consumption.
Looking for an Energy Star-certified roofing system is a good place to start. In
addition, consider the roof’s color -- white roofs reflect more heat,
decreasing the load on the cooling system -- and its moisture management
properties, as storm water runoff can take a toll on civic infrastructure and
the surrounding environment.
Roofs that are literally green, featuring grass, trees and other plants, are
becoming more common, and green designers laud them for their shading,
insulating and water absorption properties.
The roof is not the only place where green design may be, literally, green. More
and more, say architects, plants are a part of environmentally conscious
exterior design, and designers often look to Mother Nature to provide facility
solutions.
“Landscaping can help with natural shading and with blocking wind,” says
Gibney.
“There are plenty of surfaces that can be used for growing things,” says
Bill Reed, vice president of integrative design, Natural
Logic. “We see living walls and plant screens all becoming more common.”
Last but not least among the major exterior components, external walls also
affect a building’s overall environmental impact. Chiefly, say experts,
facility executives should be concerned about walls’ moisture performance, as
a poorly performing wall can lead to mold and mildew, which are major detriments
to IEQ and occupant health.
“If you’ve got stone, brick or a similar exterior façade that is, in
effect, permeable, you may want to put a moisture barrier and make sure there is
a slot in between the layers to let the moisture escape,” recommends Browning.
In addition, recommends Richelle Schoessler Lynn of LHB,
“you need a breathable finish in the interior of the exterior wall in order to
avoid mildew.”
Taking the next step
Following sound design principles and making informed product choices will stand
you in good stead where energy efficiency and IEQ -- certainly among the most
important factors in an envelope’s overall impact on both the indoor and
outdoor environment -- are concerned.
Taking the next step toward making the envelope environmentally friendly can be
another matter, as a discussion of the true life-cycle impacts of materials gets
complicated fast.
Indeed, materials specification is a science unto itself, and it’s one where
there are no clear-cut answers.
“It will always come down to tradeoffs and choices,” says Rebecca Foss, an
architect and specifier who works with both EcoDesign
Resources Inc. and the Center
for Sustainable Building Research at the University of Minnesota.
In short, however, the less energy and pollution that is generated over the sum
total of a material’s manufacturing, transportation, finishing, installation,
and use, the fewer its negative impacts on the environment.
“You have to look at the downstream and upstream implications of your
decisions,” says Reed.
For some facility executives, looking closely at the real environmental impact
of materials demands a closer look at a broader spectrum of issues. For
instance, facility executives might want to consider how much carbon dioxide is
generated by shipping stone from across the country or evaluate a product’s
recyclability.
“We’re accustomed to looking at basics like durability, ease of maintenance,
long-term adaptability and so forth, but now we’re also looking at the total
impact of extracting, producing and manufacturing materials,” says Foss.
Integration is key
So what is the secret to achieving a truly green envelope? The experts agree: an
integrated planning process.
“Everybody talks about it,” says Reed, “but few people do it well.”
And the process must be integrated on a number of levels, starting with
involving the right combination of decision-makers in the design process.
“Most architects and engineers can bring the right level of expertise to the
table,” says David Ejadi, vice president, The
Weidt Group. “But things often get short-circuited when owners don’t
bring enough of their team to the table. Make sure you get buy-in from as many
levels as possible.”
It may also mean integrating budgets and priorities in new ways.
“There are so many cases where architects have designed the envelope to be a
daylit building, and then somebody else comes along and blocks the windows or
puts in really high partitions because that’s what has always been used and
what is in the budget,” says Ejadi.
Furthermore, an integrated approach necessitates looking at building systems in
a holistic way. That is, looking at systems not just in terms of how they
operate, but how they operate relative to one another.
“People will say, ‘Let’s not use triple-glazed windows because they are
too costly,’ ” says John Carmody, director of the Center for Sustainable
Building Research at the University of Minnesota. “But in some cases owners
have been able to eliminate perimeter heating and downsize mechanical systems
enough to pay for the windows.”
Also key is integrating the design process from the beginning. If daylighting
and heat gain are considered in the design of the structure, for instance, it
may be possible to shape the building skin to shade the windows so that a less
efficient and less expensive glazing is needed. In addition, exterior choices
should be weighed in the light of their impact on the environmental soundness of
the interior.
“Use your structure so that you don’t have to add more material just to get
a nice finish on the inside walls,” says LHB’s Schoessler Lynn.
Resources for green envelope design
Fortunately for facility executives, tools are available to help sort through
the many layers of decisions involved with designing a green envelope. Energy
modeling and life-cycle costing can give facility executives a solid idea of the
costs and benefits associated with their choices before a facility is built. And
the U.S. Green
Building Council’s LEED (Leadership in Energy and Environmental Design)
Green Building Rating System provides facility executives and designers with a
framework for assessing the performance and environmental characteristics of
facilities.
“LEED is all about integrating the design process,” says Brendan Owens, lead
engineer with the U.S. Green Building Council. “It takes all the traditional
disciplines, such as mechanical, architectural, etc., and brings them together
at the very beginning of the project to establish goals.”
Unfortunately, though, some of the tools that would assist in the specifying of
products and materials for green envelopes do not yet exist. As a result, the
process of weighing all the countless pros and cons and trade-offs involved with
green design can be a difficult one.
Tools to help evaluate energy performance have been around for quite a while,
but that’s not the case when it comes to understanding the overall
environmental impact of products and materials, says Foss. “The answers on the
materials side are not got at very easily.”
Not easy being green
It’s not difficult to understand why environmental responsibility makes sense
where energy efficiency and IEQ are concerned. Green performance in both areas
translates to the bottom line in energy cost savings and productivity gains. And
green materials do not always cost more.
“We’re seeing more and more metal siding with a higher percentage of
recycled content,” says Gibney. “That sort of thing does not necessarily
cost more.”
Once you get beyond basic good, energy-efficient design, though, the benefits of
green-mindedness aren’t always as clear.
“We are still struggling with ways to get payback on some of these strategies,”
says HOK’s Nelson.
And while the benefits of environmental commitment sometimes come in forms other
than bottom-line savings, such as easier access to permits in some locations, it
takes a real organizational commitment to build an envelope that is truly green
in the fullest sense of the term. In addition, it takes an ingrained
understanding and full buy-in on goals and priorities. For example, are concerns
primarily with energy efficiency, or with the whole life-cycle impact of the
facility and issues like pollution and embodied energy?
The right architect and engineer should be critical partners in helping to sort
out the answers to these questions and determine how best to achieve goals, but
it’s crucial, experts say, not to abdicate too much responsibility.
“The green projects that really work well have all been ones where the owner’s
commitment drove the whole process,” says Reed. “The message to the
architect was, ‘We’re doing this. Now how can you make it happen?’
“It’s the difference between a drive to do the right thing and a desire to
get the right stuff.”
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This article first appeared in the September 2003 issue of Building
Operating Management.