greening roofs in edmonton

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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.

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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.

TRANSCRIPT

Page 1: Greening Roofs in Edmonton

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.

Page 2: Greening Roofs in Edmonton

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.

Page 3: Greening Roofs in Edmonton

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

Page 4: Greening Roofs in Edmonton

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).

Fig. 3. Average height of species grown in three different depths of substrate.

Fig. 4. Average width of species grown under three different depths of substrate.

Fig. 5. Percent cover of grasses and forbs, and percent bare ground for 3 different depths of

growth medium in October 2010.

0

5

10

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7.5 cm depth

10 cm depth

15 cm depth

0

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35

7.5 cm depth

10 cm depth

15 cm depth

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grasses forbs bare

Pe

rce

nt

cove

r (%

) 8 cm

10 cm

15 cm

Page 5: Greening Roofs in Edmonton

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

05

1015202530354045

Pe

rce

nt

cove

r (%

)

8 cm

10 cm

15 cm

Page 6: Greening Roofs in Edmonton

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.

Fig. 8. Snow depth at Williams engineering.

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Sno

w D

ep

th (

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Page 7: Greening Roofs in Edmonton

(a)

(b)

Fig. 9. Minimum temperature (a) at the surface and (b) at the bottom of the growth medium at

Williams Engineering.

-30

-25

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Page 8: Greening Roofs in Edmonton

(a)

(b)

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.

0

5

10

15

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25H

eig

ht(

cm)

8 cm

10 cm

15 cm

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Dia

me

ter

(cm

)

8 cm

10 cm

15 cm

Page 9: Greening Roofs in Edmonton

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

Page 10: Greening Roofs in Edmonton

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.

Page 11: Greening Roofs in Edmonton

7. Appendix

Fig. 11. Williams Engineering before green roof installation.

Fig. 12. Removal of existing roof, and installation of roofing impermeable membrane.

Page 12: Greening Roofs in Edmonton

Fig. 13. Roofing impermeable membrane.

Fig.14. Installation of root repellent membrane, and insulation. Construction of research area

plots.

Page 13: Greening Roofs in Edmonton

Fig. 15. Research plots on Williams Engineering roof.

Fig 16. Growth medium being pumped up to roof.

Page 14: Greening Roofs in Edmonton

Fig. 17. Growth medium.

Fig 18. East side of roof.

Page 15: Greening Roofs in Edmonton

Fig.19. West side of roof ( MacDonald hotel in background).

Fig. 20. Research plots 2 months later.

Page 16: Greening Roofs in Edmonton

Fig.21. West side of roof two months later.

Fig. 22. Winter view.

Page 17: Greening Roofs in Edmonton

Fig. 23. Winter view west side.

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