School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
Sustainable Building Envelope –Green Roof Technology
Dr. Karen Liu
School of Construction and the EnvironmentBritish Columbia Institute of Technology
BCBEC luncheon meeting, Feb 08, 2007
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→ Presentation Outline
1. Introduction2. Green Roof Materials3. Green Roof FAQ4. Standards and Guidelines 5. Green Roof Research at BCIT
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→
specialized roofing system that supportsvegetation growth on rooftops
A green roof in Europe
What is a Green Roof?
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→
Vancouver Public Library (HydroTech)
FeaturesDeep soil (>200 mm)Heavy weight (> 300 kg/m2)Traditional garden plants and shrubsFavourable conditionsHigh maintenancePark-like setting
Intensive Systems
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→
401 Richmond, Toronto(Xero Flor)
Extensive SystemsFeatures
Shallow medium(<200 mm)Light weight (< 300 kg/m2)Grasses, sedums and herbsHarsh conditionsLow maintenanceEcological setting
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→
Roof assembly(Conventional or PMRA)
Root resistant layer
Drainage layerFilter layer
Growing medium
Vegetation
Green Roof - Principal Components
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→ Green Roof on Conventional Roof
Cover Board
Insulation
Deck
Vapour Barrier
Membrane
Considerations:• Rooftop traffic• Load distribution
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→ Green Roof on PMRA
Insulation
Deck
Membrane
Filter cloth
Considerations:• Rooftop traffic• Load distribution• Vapour diffusion
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→ Presentation Outline
1. Introduction2. Green Roof Materials3. Green Roof FAQ4. Standards and Guidelines 5. Green Roof Research at BCIT
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→ Root Barrier - Physical
Root barrier and installation (Source: HydroTech)
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→ Root Barrier - Chemical
Root barrier chemical treated filter cloth
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→ Drainage Layer
Extensive – 3D filament mesh Extensive – dimpled system
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→ Drainage / Storage Layer
Extensive – dimple with cups
Intensive – drain channel with cups
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→ Drainage / Storage Layer
Source: greenrooftops.com
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→ Filter Membrane
Source: HydroTech
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→ Growing Medium
Soil is blown onto roof (Source: HydroTech)
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→ Examples – Sedums and Grasses
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→ Presentation Outline
1. Introduction2. Green Roof Materials3. Green Roof FAQ4. Standards and Guidelines 5. Green Roof Research at BCIT
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→
6 m (2
0 ft.)
15 m (30 ft.)
5 m
(16
ft.)
N
Green Roof Research Facility (GRRF)Parapet355 mm(14 in.)
REF GR-1GR-2
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→
Structural supportVapour control layer
Thermal insulationSupport panel
Reference Roof Green Roof
Drainage layerFilter membraneGrowing medium
Vegetation
Roof membrane
ThermocoupleHeat Flux Transducer
VB
IN
INS
SB
Layer
SM
OUT
MEM
Cross-Section of GRRF Roof
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→
GR-1
GR-2
REF
3 Test Roof Sections
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→ Growing Medium and VegetationGreen Roof “GR-2”Green Roof “GR-1”
GM = 150 mm, GrassesGM = 75 mm, Sedums
Objectives: Compare performance of GR-1 & GR-2
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→ FAQ #1: Extensive Green Roof
How much growing medium do we need?
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→ Energy EfficiencyAverage Total Daily Heat Flow Through Roof Surfaces at GRRF
(Jan 1, 2005 - Dec 31, 2005)
0.00
0.05
0.10
0.15
Winter Spring Summer Fall
Hea
t Flo
w (k
Wh/
m2/
day)
REFGR-1GR-2
Average Daily Heat Flow Through Roof Surfaces
(Jan 1, 2005 – Dec 31, 2005)
=> Thermally, GR-1 performs similarly to GR-2 in Vancouver
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→
Rainfall and Runoff in Dry Season(May 20-21, 2005)
0
0.5
1
1.5
2
2.5
1830
2030
2230 30 23
0
430
630
830
1030
1230
1430
1630
1830
2030
Rai
nfal
l / R
unof
f (m
m)
Dry Season: Apr – Sep, total rainfall = 231 mm
Dry Season Event - Vancouver
Delay
Peak Flow
Amount
May 20 May 21
RainGR-1
GR-2
Rain = 18mmGR-1 = 10mm (44%)GR-2 = 3 mm (86%)
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→
Wet Season: Oct – Mar, total rainfall = 1277 mm
Wet Season Event - Vancouver
Rainfall and Runoff in Wet Season(Apr 5-6, 2005)
0
0.2
0.4
0.6
0.8
1
1015
1215
1415
1615
1815
2015
2215 15 21
5
415
615
815
1015
1215
Rai
nfal
l / R
unof
f (m
m)
Apr 5 Apr 6
RainGR-1GR-2
Rain = 17mmGR-1 = 13mm (22%)GR-2 = 14 mm (17%)
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→
Rainfall and Roof Runoff at GRRF(Jan 1, 2005 - Dec 31, 2005)
0
50
100
150
200
250
300
350
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Rai
n / R
unof
f (m
m)
WS
GR1
GR2
Wet Dry Wet
RAIN
Runoff Retention
Wet season: reduction=15%Dry season: reduction=90%
Overall Reduction = 28%
=> Rain pattern affects retention efficiency of green roofs
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→ Other considerationsLocal Climate
Vancouver’s unique weather pattern
Summer – mild, dry; Winter – cool, wet
Effects of plant on growing mediumRoot system cause uneven flow???
Plant internal water storage, transpiration
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→ FAQ #2: Membrane Durability
Does green roof make a roof membrane last longer?
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→ What affects membrane durability?Aging
Heat, ultra-violet radiation
MechanicalThermal stresses, building movement
PhysicalWind, puncture (e.g. hail, foot traffic)
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→ Membrane Temperature - VancouverRoof Membrane Temperature - REF
(Jan 1, 2005 - Dec 31, 2005)
-20
0
20
40
60
80
Jan-
05
Jan-
05
Jan-
05
Feb-
05
Feb-
05
Mar
-05
Mar
-05
Apr
-05
Apr
-05
May
-05
May
-05
Jun-
05
Jun-
05
Jul-0
5
Jul-0
5
Jul-0
5
Aug
-05
Aug
-05
Sep-
05
Sep-
05
Oct
-05
Oct
-05
Nov
-05
Nov
-05
Dec
-05
Dec
-05
Dec
-05
Tem
pera
ture
(°C
)
TmaxTmin
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Reference Roof, GRRF 2005
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→ Membrane TemperatureRoof Membrane Temperature - GR-1
(Jan 1, 2005 - Dec 31, 2005)
-20
0
20
40
60
80
Jan-
05
Jan-
05
Jan-
05
Feb-
05
Feb-
05
Mar
-05
Mar
-05
Apr
-05
Apr
-05
May
-05
May
-05
Jun-
05
Jun-
05
Jul-0
5
Jul-0
5
Jul-0
5
Aug
-05
Aug
-05
Sep-
05
Sep-
05
Oct
-05
Oct
-05
Nov
-05
Nov
-05
Dec
-05
Dec
-05
Dec
-05
Tem
pera
ture
(°C
)
TmaxTmin
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Membrane Temperature - VancouverGreen Roof “GR-1”, GRRF 2005
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→
Statistics on Daily Maximum Temperature Jan 1 – Dec 31 ,2005
Reference Roof
No. ofDays
% ofDays
TemperatureGreater Than:
20°C
40°C
50°C
60°C
257
158
100
41
70
43
27
11
Green Roof - 1
No. ofDays
% ofDays
121
0
0
0
33
0
0
0
Green Roof - 2
No. ofDays
% ofDays
68
0
0
0
19
0
0
0
=> GRS can slow down the aging process of the roof membrane
Membrane Temperature Statistics
30°C 206 56 5 1 0 0
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→ Membrane Temperature FluctuationsMedian Daily Membrane Temperature Fluctuations
(Jan 1, 2005 - Dec 31, 2005)
19
43
48
16
24 5
21 1 1 10
10
20
30
40
50
Winter Spring Summer Fall
Tem
pera
ture
Flu
ctua
tion
(°C
)
REFGR-1GR-2
=> GRS can reduce thermal stress on the roof membrane
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→ FAQ #3: Energy Efficiency
What is the "R" value of a green roof?
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→ What is “R-value”?
R-value is a measure of thermal resistance of insulation materials
SI unit (RSI): K.m2/WImperial unit (R-value): ft2.F.h/BTU
Hot Cold
Th Tc
L
A
Q
Qt x A x ΔT
R =
Thermal Resistance (R)
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→
Thermal mass
Evapotranspiration
Insulatingproperty
Shading
Indoor
How does green roof work?
Summer
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→ Problem with “R-value”?Green roof cools a building with more than insulation
ShadingEvaporative coolingThermal mass
R-value of wet soil is low but evaporative cooling is high
What about “equivalent” R-value?
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→ FAQ #4: Lightweight Systems
Can lightweight systems perform at holding water?
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→ Extensive Green Roof Systems
Generic green roof system (75 mm)• Generic green roof growing medium (75mm)
• Vegetation carrier with growing medium (25mm)
• Water retention fleece (10 mm)
Proprietary green roof system (45 mm)
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→ Water Retention Experiment at BCIT
Generic green roof growing medium
Proprietary green roof assembly
=> Measure dry weight
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→ Water Retention Experiment at BCIT
Submerged for 24h…
Dripped for 2h…
=> Measure saturated weight
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→ Saturated Weight and Water Retention
DryWeight
SaturatedWeight
Water Retention
(L/m2)Generic Extensive GRS
46.3 kg/m2
9.4 lb/ft2
74.3 kg/m2
15.0 lb/ft2 28.0
Proprietary Extensive GRS
24.6 kg/m2
5.0 lb/ft2
49.8 kg/m2
10.1 lb/ft2 25.3
Comparison 53% 67% 90%
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→ Presentation Outline
1. Introduction2. Green Roof Materials3. Green Roof FAQ4. Standards and Guidelines5. Green Roof Research at BCIT
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→ Standards and Guidelines
Materials standards
Installation standards
Guidelines
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→
Runoff increases with roof slopeMinimum 2% for extensive GRS to allow proper positive drainage
>5%: use growing medium with high water storage capacity and vegetation with low water demand
special considerations to protect GRS against shear and sliding for steep slopes
Maximum 45o to avoid danger of sliding
GRS on pitched roof (XeroFlor)
FLL Guidelines – Roof Slopes
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→
Roots can penetrate membrane
Use protective sheeting or special treatment
Use multiple root-penetration barriers if necessary
Avoid plants with aggressive roots such as bamboo and variety of Chinese reeds
Resistance to root penetration should be tested by standard test
bamboo
FLL Guidelines – Root Penetration
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→
Maintain proper drainage
Roof outlets should be permanently accessible and not covered by greenery or gravel
Inspection shaft should be installed in outlets that are located within the planted areas
Avoid plants to grow into the gutters and block drainage path
Avoid hanging plants that block gutters at eaves on steep slopes
Roof drain and inspection chamber (HydroTech Membrane Corp.).
FLL Guidelines - Drainage
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→
Dried plant materials pose fire risk
Use growing medium that meet a composition and depth requirement
Select vegetation that has a low fire load (e.g. succulents instead of grasses)
Allow spacing between vegetation areas and any roof penetrations
Incorporate irrigation systemSedums – low fire load
FLL Guidelines – Fire Resistance
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→ Presentation Outline
1. Introduction2. Green Roof Materials3. Green Roof FAQ4. Standards and Guidelines 5. Green Roof Research at BCIT
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→ Green Roof Research at BCIT
Green Roof Research Facility at BCIT, Great Northern Way Campus
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→ CAGRT’s Partners
Roofing Systems
Firestone Building ProductsHydroTechMembrane Corp.IKO IndustriesSarnafilSiplastSoprema
Other Industry
Detec SystemLinnaea NurseryNATS NurseryNilex/J-DrainQuad-LockStream Organics Management
Green Roof Systems
Elevated Landscape TechnologiesXeroFlor CanadaZinCo Canada
BCIT-CAGRT
Agency
NSERCWDREFECGVRD –SILG
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→
• Comparativeperformancedata
• Quantitative3rd partyverification
• Increasedmarketconfidence
Roof Evaluation Module (REM)
Roof Evaluation Modules at BCIT
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→ Regional Infrastructure Network
City of White Rock Operations Building, White Rock, BC
• Electronic Arts, Burnaby
• White Rock Operations Building
• Elevated Research Platform, BCIT
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→ Education
Open House Every 3rd Thursday of the month, 3-5 pm555 Great Northern Way
Green Roof CoursesGROW 0001 workshop (4h)GROW 1000 part time (18h)GROW 3000 full time (45h)
Visit our web site: www.greenroof.bcit.ca
School of Construction and the Environment
Centre for the Advancement of Green Roof Technology
→ CAGRT Research Team
Maureen Connelly Research Program Head
Karen Liu Acting Program Head
Kerly Acosta Research Faculty
Janet Snell Research Faculty
John Compton-Smith Research Analyst
Anita Green Education Coordinator
Claro Dejeres Community and Industry Liaison
Thank You!