Green Walls and Indoor Air Quality


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Green Walls and Indoor Air Quality

  1. 1. January 19, 2009Green Walls and Indoor Air QualityBy George IrwinAll 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. 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 1900s, 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. Thefollowing are deemed by the EPA as the leading causes of SBS: inadequate ventilation; chemicalcontaminants from indoor sources; chemical contaminants from outdoor sources; and biologicalcontaminants.2Solutions and Economic Considerations of Air QualityThe solutions to remove the compounds may include pollutant source removal or modification, aneffective approach when sources are known and control is feasible. Examples include routinemaintenance of HVAC systems, e.g., periodic cleaning or replacement of filters, and increasingventilation rates by utilizing HVAC systems, at a minimum, to meet ventilation standards in localbuilding codes. However, many systems are not operated or maintained to ensure that thesedesign ventilation rates are provided. Air cleaning can be a useful adjunct to source control andventilation but has certain limitations.Particle control devices such as the typical furnace filter areinexpensive but do not effectively capture small particles;high performance air filters capture the smaller, respirableparticles but are relatively expensive to install and operate.Mechanical filters do not remove gaseous pollutants. Somespecific gaseous pollutants may be removed by adsorbentbeds, but these devices can be expensive and requirefrequent replacement of the adsorbent material. In summary,air cleaners can be useful, but have limited application and
  3. 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 tobe the solution or 100% effective and are costly.Natural FiltrationHowever, there is strong evidence on a more natural solution. This natural or holistic approach tocleaning indoor air can be as simple as adding the ecosystem that is responsible for creatingfresh air to begin with: the indoor green wall. The indoor green wall eco-system is a verycomplex order that has the ability to change; it’s a built in survival mechanism. Plants can beresilient and what may be toxic to one species is a source of survival for another. VOC’s havebeen the focus of many studies in recent years and it is now evident that data concludes over80% 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 anInterior Green Wall; Photo authentic setting the findings showed that plants work toCourtesy Elevated Landscape remove VOC’s in a real life situation. The data demonstratedTechnologies 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 asacceptable using only 3 - 6 specimens in 10” and 12” pots.So its obvious that if you are considering adding vegetation, plants or agreen wall in your building you don’t have to have an interior jungle andmasses of plants to obtain results. Conclusions of both the field studyand controlled studies strengthen the conclusion that “The potted plantmicrocosm 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; theyautomatically kick on when the VOC levels reach 100 ppb.We know that cleaning the air can be done mechanically andbiologically. The mechanical means would need to include at timescumbersome and costly equipment, require additional space,potentially cause an acoustic burden on the immediate work or livingspace, and may not prove to be 100% effective. The mechanicalmeans provides one service without any additional benefits.
  4. 4. Lets premise that the data is a direct reflection on using a soil-based potted plant; in theory thenit is assumed that for comparing green wall systems, a soil-based green Green Wall at the University ofwall would need to be considered for similar performance. The data Guelph-Humber in Torontosuggests that the VOC’s removed are a direct result from microbialreactions at the root level. Biological means of adding plants hasproven to rid the interior space of VOC’s to an acceptable level. Adding plants also offers otherbenefits 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 PremiumThe studies from the University of Technology used specimens of table and floor units / pottedplants containing Janet Craig Dracaena (Dracaena dermensis). The study needed to utilizevaluable 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 sfas a low) 6. Allowing for an area of sufficient floor space that would create the desired results ofcleansing 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 1From a monetary perspective, due to its vertical nature a green wall is less than half the cost ofoccupying any retail floor space, assuming the cost per sf in rent noted above is accurate. Oneretail 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 storewhen I would rather have merchandise; it’s just simple economics. Since we installed our greenwall not only has our store been noticed but the area has been more inviting and the commentsfrom our customers have been nothing but positive.” ~ Joe Edmond, owner of Green AcresGarden Center in Greece, NY.Floor vs. Wall Space: Get More for Your MoneyThe value of implementing such an arrangement would equate to sacrificing a conservative 35 sfof floor space x $25.50 per sf would require a monetary expenditure of $892.50 a month on
  5. 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 aestheticallypleasing and functional area of potted plants . (*For the purpose of this column the cost of plantmaintenance and other utilities were not considered and the figures mentioned are generalized asa 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. Thecost per sf has ranged from $100.00 to $175.00 per sf depending upon the system and the plantmaterial. Based on our estimated yearly cost to allocate 35 sf of floor space containing pottedplant material, a more economical option would be to consider a green wall. Utilizing the simplestof 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 2Now, 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, wouldprovide a canopy that is 100% equal to that of the design. That same 35 sf of floor space on awall is actually 35 sf of “Green Vegetation.” There are no voids and in theory as an owner of thegreen wall the air cleaning and VOC removing benefits, according to the previous data, wouldprovide an even more effective return on the investment - strictly speaking about the green areayou would get more “Green Vegetation” for your investment.More Tangible BenefitsOn a lesser note, other opportunities present themselves as tenants, clients and other buildingvisitors 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 resultis people are talking and presenting an opportunity to reflect positively about the new greenspace. After installing a green wall, one major retailer had increased traffic due to the attentionresulting in higher margins. Other tangible benefits include noise reduction, improved productivityand lower absenteeism, to name a few. According to Environmental Building News, a return oninvesting in plants would result in an annual savings of $975.00 per employee, a return oninvestment of 995%. 7
  6. 6. Environmental Building News, Vol. 13, No. 10; Figure 3Green wall design and planning require mechanical functions as well as biological. As adesigner, one of the key components to consider is how the wall will be irrigated. This is thenumber one evaluation, not any less important than the lighting, maintenance and system typebut if the wall is to include an automatic irrigation system from a constant source of water (a directconnection to a main water line), we strongly recommend an overflow built into the irrigation catchbasin. To no fault of any one system or any system installer, if there is a mechanical failure withinthe 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. Thebest 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 seean 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 forthe system to be value-engineered from the project. Design the wall as a part of the building andthe buildings ventilation system is a must-have not just for aesthetics, but for overall functionalitypurposes.Beauty and FunctionAt first, it is always the breathtaking beauty of a green wall thatis the focus. Indoors, the wall provides a reprieve of sorts fromunfavorable seasonal elements. Yet there is more to it thanthat. Studies have proven the effectiveness of potted plants toremove harmful VOC’s from our dwellings and workplaces.Green walls would provide an opportunity to add an increasedvertical canopy of “Green Vegetation” per square foot incomparison to potted plants on the horizontal plane of the floor.With sky high retail leasing costs, monetarily speaking thegreen wall is shown to be the economic choice with addedbenefits to increase marketing potential, employee productivity,preventing absenteeism and simply provide an un-measurablebenefit we call the “Wow Factor.”Next time you’re indoors and youre feeling tired, have a headache 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 areyou, and the environment. beautiful living machines.
  7. 7. George Irwin, The Green Walls EditorSources:1. http://epa.gov2. Ibid.3. Wood, R, Orwell, R, Tarran, J, Burchett, M, 2001, Pot-plants really do clean indoor air, NurseryPapers, NGIA5. Irwin is the President and CEO of Green Living™ Technologies, LLC (GLT) basedin NY. Green Living™ Technologies is the only US manufacturer of growing media basedgreen wall and three types of green roof systems. Mr. Irwin is also a trainer for GreenRoofs for Healthy Cities Green Walls 101.Contact George Irwin at:,, or1.800.631.8001.