Evaluating the environmental benefits of green wall systems planted with different Sedum species. Eighteen circular green walls were installed on the SIUE campus with different aspects and plantings. Preliminary results found that planted walls had lower surface temperatures than unplanted walls, with the greatest differences on south and west facing walls. Plant growth also varied by aspect. Stormwater retention tests found water was retained longer in planted walls compared to unplanted walls. The study aims to determine which species provide the best thermal and stormwater retention benefits of green walls.

1. Evaluating the Environmental Benefits of Green Wall Systems
Ostendorf, M.1, K. Thompson1, M. Woolbright2, S. Morgan1, S. Celik1, and W. Retzlaff1
Southern Illinois University Edwardsville1, Green Wall Ventures2
ABSTRACT
Eighteen circular (7-foot diameter) green walls (donated by Hercules
Manufacturing of St. Louis) have been located on the SIUE campus.
The project is designed to evaluate the environmental performance of
green wall systems planted with five Sedum species and one unplanted
wall on north, south, east, and west wall aspects. We have determined
that plant surface temperatures are less than wall block surface
temperatures while the growing medium (Ameren Bottom Ash) has
the greatest surface temperature. North and east wall aspects have the
lowest afternoon surface temperatures - more than 25oF lower than the
west and the south aspects. Plant growth also varies by wall aspect
which is greatest in Sedums planted on west wall aspects. In a
preliminary storm water saturation test in Fall 2009, we determined
that storm water runoff was delayed in a planted green wall compared
to a non-planted green wall. Our evaluation so far indicates that living
wall systems have the potential to reduce urban heat flux and storm
water runoff.
MATERIALS AND METHODS
Green Wall Setup – 3 replicates of 6 Green Walls each planted with one of four Sedum species, one with no plants
(the control wall), and one with mixed Sedum plug in a completely randomized design.
Green Wall Species - Sedum immergrunchen, Sedum kamtschaticum, Sedum phedimus, and Sedum spurium
The mixed Sedum species wall includes S. spurium, S. sexangulare, S. cauticola, S.
kamtschaticum, and S. album
Green Wall Medium - Bottom Ash mixed with composted pinebark donated by Ameren UE (Retzlaff et al., 2008)
Green Wall Blocks - Donated by Hercules Manufacturing of St. Louis (Retzlaff et al., 2008)
Green Wall Outlets – Each green wall is built with a base layer and a single outlet pipe (Fig. 1).
Thermal Monitoring – Wall surface temperatures on the north, south, east, and west aspects are currently being
recorded monthly, beginning in March 2010. A digital infrared thermometer is used to collect temperatures at the
same time each afternoon. A one-way ANOVA for a completely randomized design is being used to test for
differences between treatments. A Tukey’s post-hoc test is then used to rank differences at an alpha level of 0.05
(Proc GLM, SAS version 9.1).
Stormwater Retention Monitoring – Each Green Wall Outlet is fitted with a collection container and is monitored
promptly following precipitation events.
INTRODUCTION
Metropolitan areas often exhibit the Heat Island Effect, which is the phenomenon of significantly elevated temperature
within developed urban areas. Development, along with an increase in impervious surfaces, can also exacerbate
flooding (VanWoert et al., 2005). Green (living) walls may be used to help reduce the Heat Island Effect and to
minimize the elevated stormwater runoff that is associated with urbanization. When the plants of a green wall grow to
maximum coverage, their shade and evaporative capabilities should help to reduce the amount of heat that would
otherwise be absorbed by the wall material. The walls planted with Sedum species may also aid in reducing flood
potential by retaining stormwater. As a succulent plant, Sedum exhibits superior water retention capabilities and
drought resistance (Wolf and Lundholm, 2008). Evaluation of the biowalls (green walls) planted at SIUE is needed to
determine which plant species provide the greatest thermal benefits and which walls retain the most stormwater. This
study evaluates the surface temperatures and water retention volumes of 4 different Sedum species walls, a mixed
Sedum species wall, and a control wall with no plant species. We hypothesize that planted walls will have lower
surface temperatures and will retain more stormwater than unplanted walls.
DISCUSSION AND CONCLUSIONS
Significantly different temperatures and water volumes are desirable outcomes for the living wall systems under
evaluation, particularly for the control walls and planted walls. If the species provide greater coverage, then this
should lower the temperatures of the medium and of the block. The dark surface of the medium heats up, but with
maximum growth, the plant should provide shade and reduce the amount of heat absorbed. The coverage and
maximum growth can influence the temperature, and help provide optimal thermal benefits (Koehler et al., 2006).
The ability of the living wall to collect rainwater and the process of evaporation are also factors that may lead to
cooling of building material (Koehler et al., 2006). The reduction of urban storm water runoff by disconnecting
impervious surfaces is also desired (Mueller and Thompson, 2009). The preliminary saturation test conducted in Fall
2009 so far indicates that a planted wall may retain water longer than an unplanted wall.
Thermal data collection is currently underway on the SIUE walls. Water collection buckets are being constructed to
accurately evaluate water retention. Ideally, the biowalls will promote reduction in urban temperatures and rainwater
runoff volumes. Nonetheless, more study is needed to determine how great an influence biowalls can have on the
surrounding environment.
Figure 3. Mean temperatures of the green walls on the
South Aspect. (Medium with different grouping letters are
statistically different from one another).
REFERENCES:
Koehler, Dr. Manfred, 2006. Living Wall Systems- A View Back and Some Visions.
Mueller, G., and A. Thompson, October 2009. The Ability of Urban Residential Lawns to Disconnect Impervious Area from Municipal Sewer Systems. Journal of
the American Water Resources Association. 45(5): 1116-1126.
Retzlaff, W., J. Middleton, M. Woolbright, V. Jost, S. Morgan, and K. Luckett., 2008. Evaluating the Performance of the Ecoworks Living Wall System. Proceedings
Sixth Annual Greening Rooftops for Sustainable Communities Conference, Awards, and Trade Show (available www.greenroofs.org) Baltimore, MD.
VanWoert, N., D. Rowe, J. Andresen, C. Rugh, R. Fernandez and L. Xiao, 2005. Green Roof Stormwater Retention: Effects of Roof Surface, Slope and Media
Depth. Journal of Environmental Quality. 34: 1036-1044.
Wolf, D. and J. Lundholm, 2008. Water Uptake in Green Roof Microcosms: Effects of Plant Species and Water Availability. Ecological Engineering. 33: 179-186.
RESULTS
Figure 1. Each wall is designed with an overlying impervious base layer (left) to direct stormwater through a central water outlet
(right).
Figure 2. Eighteen circular living walls are being evaluated (left). Sedum species are planted in every pocket and on the top
of each wall except the unplanted control wall (planted wall on right).
Figure 5. In preliminary testing in Fall 2009, the control wall (left) was saturated for approximately 55 minutes before water
discharged from the outlet pipe. For the planted Sedum wall, water flowed through the outlet pipe after approximately 75
minutes of saturation.
A
Species
Control
Immergrunchen
Kamtschaticum
Phedimus
Spurium Mix
Temperature(
o
C)
0
5
10
15
20
25
30
A A
A
B
B
A
B
Species
Control
Immergrunchen
Kamtschaticum
Phedimus
Spurium Mix
Temperature(
o
C)
0
5
10
15
20
25
Figure 4. Mean temperatures of the green walls on the
North Aspect. (Medium with different grouping letters are
statistically different from one another).
Green Wall Temperatures on South Aspect 03/19/10 Green Wall Temperatures on North Aspect 03/19/10
RETAINING WALL