A proposal submitted in April 2009 to the Alberta Real Estate Foundation (AREF) was approved in June 2009, with some modifications. We originally had proposed to research native plants species on green sections of three commercial roofs in the city of Edmonton, and to establish and monitor these roofs. We were now to use the fund ($45,600) for one roof only, the Williams Engineering building roof.

1. AREF Report 2009-2011
Project title: Greening roofs in Edmonton
Recipient: Dr Leonie Nadeau PAg, School of Sustainable Building and Environmental
Management, NAIT
1. Introduction/background
A proposal submitted in April 2009 to the Alberta Real Estate Foundation (AREF) was
approved in June 2009, with some modifications. We originally had proposed to research native
plants species on green sections of three commercial roofs in the city of Edmonton, and to
establish and monitor these roofs. We were now to use the fund ($45,600) for one roof only, the
Williams Engineering building roof.
The original plan as proposed was to construct a green roof in sections over time, and we
wanted to establish a green roof only on a section of the Williams Engineering building.
However, since the building needed a new roof, Williams Engineering management decided to
redo the entire roof and make it a green roof with the funds provided by AREF. For this to
happen though, many of the companies involved cut down their rates so that the entire 7000
sq.ft. green roof would cost approximately $201,000. The green roof, which is including a
research area, was completed in June 2010 (see Appendix for photos).
1.1 Williams Engineering building (Fig. 1)
The Williams engineering roof was redone in spring 2010 and included a section for
researching the influence of depth of growth medium on the performance of selected plant
species. An inverted roof model replaced the previous roof. A waterproof membrane was
installed on the concrete slab then was covered by a root-repellent polyester film membrane.
This was covered by a 15-cm drainage layer, itself covered by a filter and water retention
fabric. The growth medium was added on top of this fabric. The medium chosen was provided
by Bio Roof and was a mixture of city compost and peat moss, a soil mix which follows the
recommended standards for Green Roof for Healthy City.
Research area
We are establishing 12 plots of 45 x 180 cm with four containers with a growth medium depth
of 7.5 cm (averaged to 8 cm), four containers with a depth of 10 cm, and four containers with a
depth of 15 cm (limited by the roof loading capacity). Seedling material was planted as plugs
provided free of cost by the Native Plant Producers of Alberta. These plots are along a skyline
shown on Figure 2.

2. Fig.1. Williams Engineering building aerial view, Williams Engineering Canada 10010 - 100 St
NW Edmonton.
Plugs came in 96-count seed trays, so each plug was approximately 2 cm in diameter, and 4 cm
in depth. Plugs were produced as a mixture of seventeen species : Plains mulhy (Muhlenbergia
cuspidata), blue grama grass (Bouteloua gracilis), Rocky mountain Fescue (Festuca
saximontana), June grass (Koeleria macrantha), and sandberg bluegrass (Poa secunda) are the
same grass species as tested on the Esak Consulting roof, with the addition of tufted hair grass
(Deschampsia caespitosa). Three of the five forbs are the same (wild sage (Artemisia sp.),
golden aster (Chrysopsis villosa), and blue flax (Linum lewisii)) while low goldenrod (Solidago
missouriensis) and tall cinquefoil (Potentilla arguta) are missing. Additional forb species are
wild chive (Allium schoenoprasum), northern bedstraw (Galium boreale), meadow blazingstar
(Liatris ligulistylis), slender blue penstemon (Penstemon procerus), reflexed locoweed (
Oxytropis deflexa), purple milk vetch (Astralagus agrestis), and smooth aster (Aster laevis).
These plugs were received on June 18, 2010, and planted on June 29-30. Plant growth was
monitored.

3. Fig. 2. Plan of the green roof to be installed on the Williams Engineering Building.
Photos related to the construction of Williams Engineering roof are in the appendix.
Objective:
1.1 Establish a green roof with a research area, and monitor the performance of native plants
species growing on three different depths of substrate provided by bioroof on the Williams
Engineering roof (ongoing).
1.2 Involve students in a winter survival study of green roofs (will start in Sept 2010).
1.3 Involve Wagner High School and NAIT students from biological Sciences and
Architecture Landscape Technology in indoor green roof studies and design.
2. Findings and outcomes
2.1 Summer/fall 2010
Plants grown in plugs and put in the substrate on June 29-30 2010 were measured biweekly
starting July 9 (see previous report). Plants were kept watered throughout July to favor
establishment.
The height and diameter of plants grown in each plug are plotted in Figs 3 and 4. As expected,
plants growing in the shallow depth were smaller than plants grown in 15 cm of substrate, and
this was observed within 4 weeks of planting. Species were mainly golden aster and a grass,
mainly fescue and grama grass. A few other species such as flax, chive, bedstraw, pasture sage,
meadow blazing star, pentsemon, bluegrass, and bebb’s sedge sporadically appeared in some
plugs. In September and October, percent cover of the various species was determined for each
plot using a Daubenmire frame. The shallowest depth had the least forbs, and the most bare

4. ground (Fig. 5). Golden aster, smooth aster, and blue flax did best in the 15 cm depth, while
pasture sage did better at the shallowest depth (Fig. 6).
25
20
15
10 7.5 cm depth
10 cm depth
5
15 cm depth
0
Fig. 3. Average height of species grown in three different depths of substrate.
35
30
25
20
15 7.5 cm depth
10 10 cm depth
5
15 cm depth
0
Fig. 4. Average width of species grown under three different depths of substrate.
60
8 cm
50
Percent cover (%)
10 cm
40
15 cm
30
20
10
0
grasses forbs bare
Fig. 5. Percent cover of grasses and forbs, and percent bare ground for 3 different depths of
growth medium in October 2010.

5. 45
Percent cover (%)
40
35 8 cm
30 10 cm
25
20 15 cm
15
10
5
0
Fig.6. Percent cover of selected native plant species for three different depths of growth
medium in October 2010.
2.2 Winter survival study
This is a summary of findings from a capstone students project. The three students involved
formed the group GreenTrack.
For the three roofs, plant samples were taken in mid October, early December, and then each
month from January to March. Samples of approximately 500 mL each were obtained by
chiseling the substrate around plants for each treatment. The exception was for Esak Consulting
roof, where containers were put indoors for a few days to allow for the substrate to thaw and
allow for sampling. This approach was done to avoid damage to the containers. The samples
were then brought to H.P. Wagner high school and students replanted them in pots, and
measured them weekly for 4 to 6 weeks.
Temperature measurements were taken at sampling time and represent minimum ( and
sometimes maximum) values from the period between two sampling dates.
Fig. 7. Potted samples for winter survival study.
Williams engineering building supported an extensive green roof. The snow and the growth
media were good insulators (Figs. 8 and 9). The temperature below the 15 cm-depth growth

6. medium was consistently higher than for the other two depth treatments. Temperatures below
the growth medium are much warmer than for another green roof in Edmonton on the
Edmonton Waste Management Centre. This may be related to a poorer insulation from the
Williams Engineering building and/or better insulation from the growth media on the Williams
engineering roof, compared to other green roofs in the city.
Snow melted in February, and very little was left of the roof in March.
The insulation provided by the green roof itself increased the winter temperature at the building
level on average by 3C for the shallowest depth (8 cm ) and by on average 10C for the deepest
depth ( 15 cm).
The insulation ability of the growth medium was significant.
All samples survived from the October, December, January and March sampling dates. The
February samples were damaged, and only a few survived. Only the December data are shown
here (Fig. 10). For the four sampling dates, the trend is for plants from the shallower depth to
out perform plants sampled from the deeper growth medium treatment.
30
Snow Depth (cm)
25
20
15
10
5
0
Fig. 8. Snow depth at Williams engineering.

7. (a)
0
-5
-10
8 cm
-15 10 cm
15 cm
-20
-25
-30
(b)
10
5
0
8 cm
-5
10 cm
-10
15 cm
-15
-20
-25
Fig. 9. Minimum temperature (a) at the surface and (b) at the bottom of the growth medium at
Williams Engineering.

8. (a)
25
20
Height(cm)
15
10 8 cm
10 cm
5
15 cm
0
(b)
35
30
25
Diameter (cm)
20
15 8 cm
10 10 cm
5 15 cm
0
Fig. 10. Plant (a) height and (b) diameter for the Williams Engineering roof for December
samples repotted and measured by the H.P. Wagner high school students.

9. Finally, plant species that overwintered best were grasses (fescue, blue grass, grama grass)
(Table 1).
Table 1. List of species in each sample for three sampling dates.
Samples from 1-Nov Samples from 3-Dec Samples from 3-Jan
fescue grama grass fescue
chives fescue, aster fescue
fescue golden aster fescue, golden aster
fescue, blue flax sage, golden aster fescue, blue flax
fescue fescue, grama grass fescue, blue flax
fescue, golden aster, weedy seedling grama grass grama grass, smooth
aster
grama grass fescue fescue, blue flax
fescue muhly, golden aster fescue
fescue golden aster, pentsemon, fescue grama grass, golden
aster
chive, grama grass,flax grama grass, weed seedling fescue
golden aster, blue grass fescue, golden aster yarrow, fescue, chive
flax grama grass fescue, grama grass
3. Partners
Alberta Real Estate Foundation
Esak Consulting Ltd
Solstice Canada Corp.
Williams Engineering
City of Edmonton
Waste Management Centre
Alberta Innovates Technology Futures (previously Alberta Research Council)
Bachelor of technology, NAIT
Biological Sciences
Landscape Architecture Design program
4. Students and others involved
NAIT Capstone students from the BTech program
Wagner high School students
NAIT staff: Klay Dyers, Joseph Varughese, Don Stewart, Dave Critchley
Maureen Elhaton and Amanda Moss, horticulture teachers at Wagner High School
5. Summary and conclusion
Logistics involved in the establishments of green roofs have been time consuming but resulted
in research activities on three roofs in Edmonton. It takes three years for green roofs to get fully
established, so it is expected that research will continue on the Williams Engineering roof for
the next few years. Results demonstrated that the performance of plant species is only

10. moderately affected by the depth of growth medium in which they were growing and that they
all survived the environmental conditions on this roof even when 8 cm of growth medium were
used.
6. Acknowledgments
We would like to extend our gratitude to The Alberta Real Estate Foundation for providing
“seed” funding that initiated the construction of the Williams Engineering green roof. Many
thanks to Gord Rajewski, Regional Director, Northern Alberta, Williams Engineering Canada
Inc., who oversaw the construction of the roof, Derek Semeniuk from Tremco Roofing Canada
who donated roofing material, Dow who provided the insulation, BioRoof Systems who
designed the roof, and Erscon and Bal4 who did the installation. We also would like to
acknowledge the Alberta Irrigation Supply and Erskine Environmental who contributed
materials and services, the Health Care of Ontario Pension Plan, owner of the building, and
TONKO, the property managers. Plants for the research portion of the roof were donated by the
Native Plant Producers Society of Alberta. We are especially grateful to Carolina Peret who
helped with establishing the research portion of the roof and with collecting data, and to Lynette
and Stephanie Esak who took very good care of seedling plugs and helped in planting them.
Special thanks to Ryan Boyd, Ruth Bucknell and Yancey Corden who were responsible for a
winter survival study as part of their Capstone project in the Bachelor of Technology program
at NAIT, and to H.P. Wagner high school students and their teachers, Maureen Elhatton and
Amanda Moss, who helped with this study.

11. 7. Appendix
Fig. 11. Williams Engineering before green roof installation.
Fig. 12. Removal of existing roof, and installation of roofing impermeable membrane.

12. Fig. 13. Roofing impermeable membrane.
Fig.14. Installation of root repellent membrane, and insulation. Construction of research area
plots.

13. Fig. 15. Research plots on Williams Engineering roof.
Fig 16. Growth medium being pumped up to roof.

14. Fig. 17. Growth medium.
Fig 18. East side of roof.

15. Fig.19. West side of roof ( MacDonald hotel in background).
Fig. 20. Research plots 2 months later.

16. Fig.21. West side of roof two months later.
Fig. 22. Winter view.

17. Fig. 23. Winter view west side.
.