Greening Roofs in Edmonton


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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.

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Greening Roofs in Edmonton

  1. 1. AREF Report 2009-2011Project title: Greening roofs in EdmontonRecipient: Dr Leonie Nadeau PAg, School of Sustainable Building and EnvironmentalManagement, NAIT1. Introduction/backgroundA proposal submitted in April 2009 to the Alberta Real Estate Foundation (AREF) wasapproved in June 2009, with some modifications. We originally had proposed to research nativeplants species on green sections of three commercial roofs in the city of Edmonton, and toestablish and monitor these roofs. We were now to use the fund ($45,600) for one roof only, theWilliams Engineering building roof.The original plan as proposed was to construct a green roof in sections over time, and wewanted 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 toredo the entire roof and make it a green roof with the funds provided by AREF. For this tohappen though, many of the companies involved cut down their rates so that the entire 7000sq.ft. green roof would cost approximately $201,000. The green roof, which is including aresearch 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. 2. Fig.1. Williams Engineering building aerial view, Williams Engineering Canada 10010 - 100 StNW Edmonton.Plugs came in 96-count seed trays, so each plug was approximately 2 cm in diameter, and 4 cmin depth. Plugs were produced as a mixture of seventeen species : Plains mulhy (Muhlenbergiacuspidata), blue grama grass (Bouteloua gracilis), Rocky mountain Fescue (Festucasaximontana), June grass (Koeleria macrantha), and sandberg bluegrass (Poa secunda) are thesame 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 (Solidagomissouriensis) and tall cinquefoil (Potentilla arguta) are missing. Additional forb species arewild 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 wasmonitored.
  3. 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 plantsspecies growing on three different depths of substrate provided by bioroof on the WilliamsEngineering 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 andArchitecture Landscape Technology in indoor green roof studies and design.2. Findings and outcomes 2.1 Summer/fall 2010Plants grown in plugs and put in the substrate on June 29-30 2010 were measured biweeklystarting July 9 (see previous report). Plants were kept watered throughout July to favorestablishment.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, andthis 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 someplugs. In September and October, percent cover of the various species was determined for eachplot using a Daubenmire frame. The shallowest depth had the least forbs, and the most bare
  4. 4. ground (Fig. 5). Golden aster, smooth aster, and blue flax did best in the 15 cm depth, whilepasture sage did better at the shallowest depth (Fig. 6). 25 20 15 10 7.5 cm depth 10 cm depth 5 15 cm depth 0Fig. 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 0Fig. 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 bareFig. 5. Percent cover of grasses and forbs, and percent bare ground for 3 different depths ofgrowth medium in October 2010.
  5. 5. 45 Percent cover (%) 40 35 8 cm 30 10 cm 25 20 15 cm 15 10 5 0Fig.6. Percent cover of selected native plant species for three different depths of growthmedium in October 2010.2.2 Winter survival studyThis is a summary of findings from a capstone students project. The three students involvedformed the group GreenTrack. For the three roofs, plant samples were taken in mid October, early December, and then eachmonth from January to March. Samples of approximately 500 mL each were obtained bychiseling the substrate around plants for each treatment. The exception was for Esak Consultingroof, where containers were put indoors for a few days to allow for the substrate to thaw andallow for sampling. This approach was done to avoid damage to the containers. The sampleswere then brought to H.P. Wagner high school and students replanted them in pots, andmeasured them weekly for 4 to 6 weeks.Temperature measurements were taken at sampling time and represent minimum ( andsometimes 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 growthmedia were good insulators (Figs. 8 and 9). The temperature below the 15 cm-depth growth
  6. 6. medium was consistently higher than for the other two depth treatments. Temperatures belowthe growth medium are much warmer than for another green roof in Edmonton on theEdmonton Waste Management Centre. This may be related to a poorer insulation from theWilliams Engineering building and/or better insulation from the growth media on the Williamsengineering 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 buildinglevel on average by 3C for the shallowest depth (8 cm ) and by on average 10C for the deepestdepth ( 15 cm).The insulation ability of the growth medium was significant.All samples survived from the October, December, January and March sampling dates. TheFebruary samples were damaged, and only a few survived. Only the December data are shownhere (Fig. 10). For the four sampling dates, the trend is for plants from the shallower depth toout perform plants sampled from the deeper growth medium treatment. 30 Snow Depth (cm) 25 20 15 10 5 0Fig. 8. Snow depth at Williams engineering.
  7. 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 -25Fig. 9. Minimum temperature (a) at the surface and (b) at the bottom of the growth medium atWilliams Engineering.
  8. 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 0Fig. 10. Plant (a) height and (b) diameter for the Williams Engineering roof for Decembersamples repotted and measured by the H.P. Wagner high school students.
  9. 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-Janfescue grama grass fescuechives fescue, aster fescuefescue golden aster fescue, golden asterfescue, blue flax sage, golden aster fescue, blue flaxfescue fescue, grama grass fescue, blue flaxfescue, golden aster, weedy seedling grama grass grama grass, smooth astergrama grass fescue fescue, blue flaxfescue muhly, golden aster fescuefescue golden aster, pentsemon, fescue grama grass, golden asterchive, grama grass,flax grama grass, weed seedling fescuegolden aster, blue grass fescue, golden aster yarrow, fescue, chiveflax grama grass fescue, grama grass3. 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 program4. 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 School5. Summary and conclusionLogistics involved in the establishments of green roofs have been time consuming but resultedin research activities on three roofs in Edmonton. It takes three years for green roofs to get fullyestablished, so it is expected that research will continue on the Williams Engineering roof forthe next few years. Results demonstrated that the performance of plant species is only
  10. 10. moderately affected by the depth of growth medium in which they were growing and that theyall survived the environmental conditions on this roof even when 8 cm of growth medium wereused.6. AcknowledgmentsWe 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. Manythanks to Gord Rajewski, Regional Director, Northern Alberta, Williams Engineering CanadaInc., who oversaw the construction of the roof, Derek Semeniuk from Tremco Roofing Canadawho donated roofing material, Dow who provided the insulation, BioRoof Systems whodesigned the roof, and Erscon and Bal4 who did the installation. We also would like toacknowledge the Alberta Irrigation Supply and Erskine Environmental who contributedmaterials and services, the Health Care of Ontario Pension Plan, owner of the building, andTONKO, the property managers. Plants for the research portion of the roof were donated by theNative Plant Producers Society of Alberta. We are especially grateful to Carolina Peret whohelped with establishing the research portion of the roof and with collecting data, and to Lynetteand 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 awinter survival study as part of their Capstone project in the Bachelor of Technology programat NAIT, and to H.P. Wagner high school students and their teachers, Maureen Elhatton andAmanda Moss, who helped with this study.
  11. 11. 7. AppendixFig. 11. Williams Engineering before green roof installation.Fig. 12. Removal of existing roof, and installation of roofing impermeable membrane.
  12. 12. Fig. 13. Roofing impermeable membrane.Fig.14. Installation of root repellent membrane, and insulation. Construction of research areaplots.
  13. 13. Fig. 15. Research plots on Williams Engineering roof.Fig 16. Growth medium being pumped up to roof.
  14. 14. Fig. 17. Growth medium.Fig 18. East side of roof.
  15. 15. Fig.19. West side of roof ( MacDonald hotel in background).Fig. 20. Research plots 2 months later.
  16. 16. Fig.21. West side of roof two months later.Fig. 22. Winter view.
  17. 17. Fig. 23. Winter view west side..