The following are answers to commonly asked questions about NEDLAW active Living Walls:
Why is indoor air quality a problem?
What’s traditionally done to maintain indoor air quality?
Why do we need an alternative approach?
What is the alternative to ventilation?
How do Living Walls work as a biofilter?
What is the difference between active and passive Living Walls?
What do NEDLAW active Living Wall biofilters look like?
Is anyone else trying this approach?
How was it designed to work?
What breaks down the pollutants?
If microbes are metabolizing most of the pollutants, why include the green plants?
Why so much diversity?
Is the system modeled after a particular ecosystem?
Could native plants be used in the system?
How long do the plants survive in the space?
Are pesticides used in the wall?
How much maintenance does a Living Wall require?
How good is air quality from an active Living Wall?
How well does the system work?
What's the difference between installing an active Living Wall and simply putting a large number of plants in your space?
How large should the Living Wall be for a typical building?
Can anyone build a NEDLAW Living Wall?
Why is indoor air quality a problem?
With winter temperatures often below -30°C (-22°F) and summer temperatures
frequently above 35°C (85°F), the North American climate can only be
described as extreme. To maintain an adequate and economical work environment,
modern buildings are as airtight as possible. The upside of being airtight
is a limit to the cost of heating or cooling the space while providing a comfortable
work space for the occupants. The downside of being airtight is that any pollutants
arising within the space — from building materials, activities or the
occupants themselves — may accumulate. This accumulation of pollutants
can influence the enjoyment, productivity, and potentially the health of the
occupants in that space. The principal indoor pollutants of concern to us are
VOCs (volatile organic compounds). VOCs arise from many sources, including
solvents, building materials, adhesives, carpets, electronic equipment and cleaning
fluids.
Return to the top
What’s traditionally done to maintain indoor air quality?
To avoid the build-up of VOCs and other indoor air contaminants, most buildings
bring in outside air through a ventilation system to displace a proportion of
the inside air. This is the modern equivalent to opening a window.
Return to the top
Why do we need an alternative approach?
During the extremes of summer and winter the new fresh
air being pumped in can be far below the quality desired by people in their work
environment in terms of temperature and humidity. Consider working at a desk
in front of an open window in the middle of winter and you will quickly realize
the value of air-handling systems designed to precondition incoming air.
Conditioning the introduced air requires substantial energy and therefore
represents a significant cost to the operation of the building. The heating
or cooling of this new air means the building manager faces the choice
of either allowing the operating cost of the building to increase or allowing
indoor air quality to decrease. An alternative that allows the maintenance of
indoor air quality without the introduction of outside air would avoid the dilemma
altogether.
Return to the top
What is the alternative to ventilation?
NEDLAW Living Walls proposes a natural solution. Rather than introducing large
amounts of so-called fresh air from outside, we incorporate into
the building itself the features responsible for making outdoor air fresh in
the first place. That is, we integrate a complex ecosystem as a biological filter
into the building's air-handling system. This removes pollutants from the
air, and removes them through normal biological processes.
Return to the top
How do Living Walls work as a biofilter?
Nature has the built-in capacity to adjust to environmental changes. It can
repair itself after damage or adapt to exposure from a wide range of compounds.
Although the time scale may vary from minutes to centuries, in time a natural
ecosystem can repair almost any damage it may sustain. For example, given enough
time nature can restore a site contaminated with organic compounds such as VOCs.
One reason for this is that, frequently, materials such as VOCs that are toxic
to some life are food for others. Most of the biological breakdown of VOCs is
done by microbes (bacteria), although higher plants may also be involved. Some
pollutant-degrading species are usually present and active in most environments,
and the act of introducing the pollutant only increases their relative numbers
and/or activity levels. NEDLAW active Living Walls are a biofilter containing
such organisms to remove contaminants present in the air at very low concentrations.
In essence, we mimic indoors what happens outdoors every day.
Return to the top
What is the difference between active and passive living walls?
There two types of living walls: active and passive. Passive living walls are
simply exterior, or sometimes interior, walls of green plants. The impact of
these plant walls on air quality is questionable. On the other hand, NEDLAW active
Living Walls actively draw air through the root zone of the plants where the
real breakdown of pollutants occurs.
Return to the top
What do NEDLAW active Living Wall biofilters look like?
A wall covered in plants, our systems is essentially vertical hydroponics. Water
from a basin planting is lifted by a pump system to the top and flows back through
the interior of the plant wall, circulating through a closed water loop system.
Return to the top
Is anyone else trying this approach?
To the best of our knowledge, the NEDLAW patented system is the only one
to use plant walls as biofilters to control indoor air quality.
Return to the top
How was it designed to work?
Filtration takes place right in the active Living Wall. Basically, dirty
air, drawn in from indoor space, makes close contact with the constantly-flowing
water within the wall. Pollutants are moved from air to water —
all the while improving air quality. Once dissolved into the water, pollutants
are attacked by biological components on the wall itself, and are metabolized
into a harmless state.
Return to the top
What breaks down the pollutants?
Although plants are able to remove some VOCs, the majority of the breakdown
is done by the beneficial microorganisms present in the system.
Return to the top
If microbes are metabolizing most of the pollutants, why include the
green plants?
Green plants are included for a number of reasons: They offer ecological stability
to the system as a whole by providing species diversity. They also may be
active at removing some VOCs to some degree. Furthermore, the inclusion of plants
adds important aesthetic value to the space. Of course, since CO2 is considered
an indoor pollutant, green plants, through the process of photosynthesis, offer
a means to control it.
Return to the top
Why so much diversity?
Species diversity gives the system ecological stability. This is very important
in order to give the ecosystem the power to deal with a broad range of potential
challenges in the indoor setting.
Return to the top
Is the system modeled after a particular ecosystem?
Rather than trying to duplicate a particular outdoor ecosystem, NEDLAW
active Living Walls are designed for the unique indoor environment. Just as
the best place for a Brazilian rainforest is Brazil, the plants used in our
walls have been selected for their adaptations to the moderate temperature,
humidity and light conditions typically found indoors. Although many are exotic
and unusual plants, some are quite common.
Return to the top
Could native plants be used in the system?
Some native plants may be present. However, most native plants would not survive
well indoors. Plants adapt to their local climate and, as such, plants from
northern climates generally require the different seasons to grow properly.
For most native plants to survive indoors, the climate in the wall would have
to mimic these seasons, making routine use of the space difficult and its performance
irregular.
Return to the top
How long do the plants survive in the space?
We expect about 90% survival of the plants each year; but this is largely
dependent on the choice of plants and local conditions.
Return to the top
Are pesticides used in the wall?
We use only methods that can be considered organic to control pests in our walls;
we emphasize management practices and biological controls such as predators.
So-called pests such as white flies, fungus gnats, spider mites and their respective
predator species are necessary, even desirable. They contribute to the ecosystem’s
species diversity and ecological stability.
Return to the top
How much maintenance does a Living Wall require?
We carry out scheduled maintenance on our Living Walls every month. Some clients
choose more frequent visits based upon their unique conditions.
Return to the top
How good is air quality from an active Living Wall?
The air quality of a space relying almost entirely on active Living Walls is
as good as, or better than, similar indoor spaces relying on sophisticated
ventilation systems that replace the building air up to six times per hour.
Return to the top
How well does the system work?
During studies at the University of Guelph, we released into the wall very
low concentrations of some common indoor pollutants to measure the system’s
potential as a filter. The chemicals were formaldehyde, toluene and trichloroethylene
(TCE). These were selected to represent the wide range of chemicals, with which
the system would need to deal. Formaldehyde is very soluble in water and readily
metabolized by bacteria and higher plants. Toluene is slightly soluble and degraded
by a select microbial population. TCE is relatively insoluble and resistant
to biological degradation.
A single pass through the Living Wall removed up to 80% of the formaldehyde,
50% of the toluene and 10% of TCE. These numbers are incredibly impressive,
particularly when you consider that the filter is only 5 cm thick. Concentrations
of toluene and formaldehyde in the aquatic system did not increase during the
four-week experiment, suggesting that these materials were readily metabolized.
TCE levels in the aquatic system initially did increase slightly, but then plateaued,
suggesting a possible capability to degrade this compound. Even before
the challenge, we knew that two to three percent of the bacteria present had
the ability to breakdown VOCs.
Return to the top
What's the difference between installing an active Living Wall
and simply putting a large number of plants in your space?
Some suggest that plants may remove VOCs from their surrounding environment.
However, there is very little available data to support this claim. Most studies
which find any VOC removal with potted plants suggest it is in the potting soil
(where the beneficial microbes live), not the green plant, where the breakdown
occurs. Others believe that even if plants can clean the air, they could only
clean a very thin layer of air immediately around their leaves. When a plant
is simply placed on a desk or even in a grouping on a wall, the typical low
rates of air movement around it would limit its impact on the air, in the space
as a whole. By actively drawing air through a NEDLAW Living Wall, we force pollutants
to the root zone where real breakdown can occur.
Return to the top
How large should the Living Wall be for a typical building?
Although there are many factors to be considered, the quickest and easiest estimate
for sizing a Living Wall is one square metre of active Living Wall to meet
the needs of 100 square metres of floor space. Our design team can work with
you to develop more accurate sizing for your particular application.
Return to the top
Can anyone build a NEDLAW Living Wall?
Aspects of Nedlaw living walls are proprietary and can not be executed without the installer
having rights to the technology. Failing to have these rights may expose the installer,
contractor, other consultants and client to legal action.
Return to the top