Green Walls and Indoor Air Quality

1. January 19, 2009
Green Walls and Indoor Air Quality
By George Irwin
All Photos Courtesy George Irwin, unless noted
What a relief it was to escape
inside a friendly tropical office
from the mounds of snow we
have here in the Northeast and
see lush green vegetation
protruding from a wall deep
into the long hallway.
It seemed as if it were a mirage
as I walked closer to the wall,
as a feeling of warm and moist
air filled the corridor, removing
my thoughts of the extreme
cold
outside back home. If
you’re lucky enough to live in a
moderate climate during the
harsh northern winters, you will
more than likely have to endure
a rainy season, but at least it’s
Compare this wall to the one below!
warm.
This is exactly what happened to me after a visit to San Pedro Sula in Honduras a few weeks
ago - the moist humid air was a welcome relief from the dry cold winter of the Northeast.
Green Living™ Wall in Tropical Honduras;
Photo Provided by Techos Verdes

2. Sick Building Syndrome and Indoor Air Quality
Back to reality, I’m from Rochester, New York, and we
are currently buried in snow and cold. The wall I was
standing next to in Honduras offered a reprieve from the
reality of the weather outside. During all seasons,
occupants inside offices and homes alike are suffering
from dry air - from cracking skin to coughing and
congestion from people with whom we share the space.
Actually, these are some common symptoms described
by the U.S. Environmental Protection Agency which are
indicators of Sick Building Syndrome (SBS). Other
more severe indicators include: dizziness and nausea;
difficulty in concentrating; fatigue; and sensitivity to
odors.1
What causes SBS and how can adding green walls
help? The costs and potential payback are detailed in
this article for the commercial property owner, designer,
or architect who will be able to utilize this to inform
clients.
Multiple sources contribute SBS to having a direct
In the early and mid 1900's, relationship with indoor air quality (IAQ). Buildings,
building ventilation standards especially newer construction, are built to be air tight to
called for 15 cubic feet per minute provide a comforting environment with heat and air
of outside air for each building conditioning. The adverse result is the lack of air
occupant primarily to remove body circulation and proper filtration. Inadequate ventilation
odors. is also a result of HVAC equipment that is either
outdated or lacks sufficient means to distribute air. The
following are deemed by the EPA as the leading causes of SBS: inadequate ventilation; chemical
contaminants from indoor sources; chemical contaminants from outdoor sources; and biological
contaminants.2
Solutions and Economic Considerations of Air Quality
The solutions to remove the compounds may include pollutant source removal or modification, an
effective approach when sources are known and control is feasible. Examples include routine
maintenance of HVAC systems, e.g., periodic cleaning or replacement of filters, and increasing
ventilation rates by utilizing HVAC systems, at a minimum, to meet ventilation standards in local
building codes. However, many systems are not operated or maintained to ensure that these
design ventilation rates are provided. Air cleaning can be a useful adjunct to source control and
ventilation but has certain limitations.
Particle control devices such as the typical furnace filter are
inexpensive but do not effectively capture small particles;
high performance air filters capture the smaller, respirable
particles but are relatively expensive to install and operate.
Mechanical filters do not remove gaseous pollutants. Some
specific gaseous pollutants may be removed by adsorbent
beds, but these devices can be expensive and require
frequent replacement of the adsorbent material. In summary,
air cleaners can be useful, but have limited application and

3. can be expensive. According to the EPA, clearly the mechanical means of removing toxins,
particles, and Volatile Organic Compounds (VOC’s) from buildings are options, but none claim to
be the solution or 100% effective and are costly.
Natural Filtration
However, there is strong evidence on a more natural solution. This natural or holistic approach to
cleaning indoor air can be as simple as adding the ecosystem that is responsible for creating
fresh air to begin with: the indoor green wall. The indoor green wall eco-system is a very
complex order that has the ability to change; it’s a built in survival mechanism. Plants can be
resilient and what may be toxic to one species is a source of survival for another. VOC’s have
been the focus of many studies in recent years and it is now evident that data concludes over
80% of VOC’s can be removed by plants.3
NASA (1984) published one of the first studies demonstrating
that plants can help to remove VOCs from sealed indoor
environments (Wolverton, n.d.).4 Later researches confirmed
these findings and also suggested that micro-organisms of
the soil might also be involved in removing toxic VOCs.
Certain plant species can remove up to 100% of the air-borne
VOCs within a 24 hour period. Some of the top performing
plants include: Howea forsteriana (Kentia palm);
Spathiphyllum wallisii var. Petite (Peace Lily); and Dracaena
deremensis var. Janet Craig (Janet Craig Dracaena),
(Burchett et al, 2001). Most recently (March 2005), The
Plants and Environmental Quality Group at the University of
Technology in Sydney concluded that both the plant
metabolism and the soil microorganisms are involved in
removing the VOCs from the air.5
Prior to the University of Technology (Sydney), other studies
were conducted in controlled laboratory test chambers. In an
Interior Green Wall; Photo authentic setting the findings showed that plants work to
Courtesy Elevated Landscape remove VOC’s in a real life situation. The data demonstrated
Technologies that both floor and table specimens, in air conditioned and
non-air conditioned space, were effective in reducing the
VOC’s to ~100 ppb (parts per billion) - regarded as
acceptable using only 3 - 6 specimens in 10” and 12” pots.
So it's obvious that if you are considering adding vegetation, plants or a
green wall in your building you don’t have to have an interior jungle and
masses of plants to obtain results. Conclusions of both the field study
and controlled studies strengthen the conclusion that “The potted plant
microcosm is an effective, self regulating indoor-air-cleaning-system for
‘bioremediation of indoor air or phytoremediation of indoor air quality,"
(Burchett et al, 2005). The plants are also self regulating; they
automatically kick on when the VOC levels reach 100 ppb.
We know that cleaning the air can be done mechanically and
biologically. The mechanical means would need to include at times
cumbersome and costly equipment, require additional space,
potentially cause an acoustic burden on the immediate work or living
space, and may not prove to be 100% effective. The mechanical
means provides one service without any additional benefits.

4. Let's premise that the data is a direct reflection on using a soil-based potted plant; in theory then
it is assumed that for comparing green wall systems, a soil-based green
Green Wall at the University of
wall would need to be considered for similar performance. The data
Guelph-Humber in Toronto
suggests that the VOC’s removed are a direct result from microbial
reactions at the root level. Biological means of adding plants has
proven to rid the interior space of VOC’s to an acceptable level. Adding plants also offers other
benefits that include aesthetics, raising humidity levels to the air during the dry seasonal months,
and they also offer opportunities of marketing value.
Commercial Floor Space Comes at a Premium
The studies from the University of Technology used specimens of table and floor units / potted
plants containing Janet Craig Dracaena (Dracaena dermensis). The study needed to utilize
valuable floor space to house the pots. In the United States, on average retail and office space is
$25.50 per sf (New York City averages $38.00 per sf as a high and Iowa averages $13.60 per sf
as a low) 6. Allowing for an area of sufficient floor space that would create the desired results of
cleansing the air of VOC’s and provide an aesthetic value would require six potted plants @ 10” –
12“ deep, or the equivalent of 35 square feet.
6 – 12” Potted Plants, Figure 1
From a monetary perspective, due to its vertical nature a green wall is less than half the cost of
occupying any retail floor space, assuming the cost per sf in rent noted above is accurate. One
retail store and green wall owner recently said:
“I’m reluctant to find the money to spend on plants that take up floor space in our retail store
when I would rather have merchandise; it’s just simple economics. Since we installed our green
wall not only has our store been noticed but the area has been more inviting and the comments
from our customers have been nothing but positive.” ~ Joe Edmond, owner of Green Acres
Garden Center in Greece, NY.
Floor vs. Wall Space: Get More for Your Money
The value of implementing such an arrangement would equate to sacrificing a conservative 35 sf
of floor space x $25.50 per sf would require a monetary expenditure of $892.50 a month on

5. potential floor space that could be otherwise be dedicated to another desk or, in a retail space,
more merchandise on the floor. Looking at the long term expense based on a yearly value,
$892.50 per month for floor space x 12 months is $10,710.00 per year for an aesthetically
pleasing and functional area of potted plants . (*For the purpose of this column the cost of plant
maintenance and other utilities were not considered and the figures mentioned are generalized as
a base line comparison to evaluate other budgetary options.)
The current market for an indoor green wall has increased to rival that of an exterior wall. The
cost per sf has ranged from $100.00 to $175.00 per sf depending upon the system and the plant
material. Based on our estimated yearly cost to allocate 35 sf of floor space containing potted
plant material, a more economical option would be to consider a green wall. Utilizing the simplest
of green wall systems and the lowest of initial cost per square foot, the wall could be as low as
$3,500 for the same 35 square feet of floor space.
Figure 2
Now, in reality that original floor space of 35 sf was not 35 sf of complete “Green Vegetation”
primarily due to the voids of the potted plants. (See Fig. 2) The green wall, however, would
provide a canopy that is 100% equal to that of the design. That same 35 sf of floor space on a
wall is actually 35 sf of “Green Vegetation.” There are no voids and in theory as an owner of the
green wall the air cleaning and VOC removing benefits, according to the previous data, would
provide an even more effective return on the investment - strictly speaking about the green area
you would get more “Green Vegetation” for your investment.
More Tangible Benefits
On a lesser note, other opportunities present themselves as tenants, clients and other building
visitors with green walls extend comments like, “I wish there was more of these plants,” “Cool,”
“Are they real?”, “The room smells so much better,” “What a relief from the cubicles!” The result
is people are talking and presenting an opportunity to reflect positively about the new green
space. After installing a green wall, one major retailer had increased traffic due to the attention
resulting in higher margins. Other tangible benefits include noise reduction, improved productivity
and lower absenteeism, to name a few. According to Environmental Building News, a return on
investing in plants would result in an annual savings of $975.00 per employee, a return on
investment of 995%. 7

6. Environmental Building News, Vol. 13, No. 10; Figure 3
Green wall design and planning require mechanical functions as well as biological. As a
designer, one of the key components to consider is how the wall will be irrigated. This is the
number one evaluation, not any less important than the lighting, maintenance and system type
but if the wall is to include an automatic irrigation system from a constant source of water (a direct
connection to a main water line), we strongly recommend an overflow built into the irrigation catch
basin. To no fault of any one system or any system installer, if there is a mechanical failure within
the irrigation components the water will be diverted into the overflow preventing any flooding.
Another option is to have a reservoir of irrigation simply re-circulated throughout the wall. The
best advice is to talk to the system manufacturer or installer about your irrigation options.
In previous articles I have written about various green wall systems, definitions and applications.
I’m going to premise a topic that I will eventually write about at a later date, but currently we see
an opportunity to integrate mechanical and biological means of using green walls as a bio-filter.
When designing a green wall as integration into the building there is much less of a chance for
the system to be value-engineered from the project. Design the wall as a part of the building and
the building's ventilation system is a must-have not just for aesthetics, but for overall functionality
purposes.
Beauty and Function
At first, it is always the breathtaking beauty of a green wall that
is the focus. Indoors, the wall provides a reprieve of sorts from
unfavorable seasonal elements. Yet there is more to it than
that. Studies have proven the effectiveness of potted plants to
remove harmful VOC’s from our dwellings and workplaces.
Green walls would provide an opportunity to add an increased
vertical canopy of “Green Vegetation” per square foot in
comparison to potted plants on the horizontal plane of the floor.
With sky high retail leasing costs, monetarily speaking the
green wall is shown to be the economic choice with added
benefits to increase marketing potential, employee productivity,
preventing absenteeism and simply provide an un-measurable
benefit we call the “Wow Factor.”
Next time you’re indoors and you're feeling tired, have a head
ache or dry itchy skin, think about what adding soothing, living,
breathing plants to a space can do for you, the people around Green Living™ Walls are
you, and the environment. beautiful living machines.

7. George Irwin, The Green Walls Editor
Sources:
1. http://epa.gov
2. Ibid.
3. http://www.wolvertonenvironmental.com/
4. Wood, R, Orwell, R, Tarran, J, Burchett, M, 2001, Pot-plants really do clean indoor air, Nursery
Papers, NGIA
5. http://www.nipa.asn.au/docs/mburchett_transcript_040305.pdf
6.
http://staging.okcommerce.gov/test1/dmdocuments/2007_CostofDoingBusiness_Index_Milken_In
stitute_2208072241.pdf
7. http://www.buildinggreen.com/articles/IssueTOC.cfm?Volume=13&Issue=10
George Irwin is the President and CEO of Green Living™ Technologies, LLC (GLT) based
in NY. Green Living™ Technologies is the only US manufacturer of growing media based
green wall and three types of green roof systems. Mr. Irwin is also a trainer for Green
Roofs for Healthy Cities Green Walls 101.
Contact George Irwin at: George@AGreenroof.com, www.agreenroof.com, or
1.800.631.8001.