Thermal Performance of Green Roofs · Summary Energy Efficiency – Green roofs can reduce the heat...
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Thermal Performance of Green Roofs Karen Liu, National Research Council Canada
Transcript of Thermal Performance of Green Roofs · Summary Energy Efficiency – Green roofs can reduce the heat...
Thermal Performance of Green Roofs
Karen Liu, National Research Council Canada
What is a Green Roof?
specialized roofing system that supportsvegetation growth on rooftops
A residential GRS in Europe
Intensive System Extensive System
Vancouver Public Library (HydroTech Membrane Corp)
Green Roof Research Facility at British Columbia Institute of
Technology
Types of Green Roofs
Roof assembly(Conventional or PMRA)
Root resistant layer
Drainage layer
Filter layer
Growing medium
Vegetation
Principal Components
Thermal mass
Evapotranspiration
Insulatingproperty
Shading
Indoor
How does it work?
• Multiple Benefits for Urban Areas– reduce energy demand– mitigate urban heat island– reduce stormwater runoff– improve air quality– replace displaced landscape– enhance biodiversity– provide recreational spaces
Podium Roof onToronto City Hall
Benefits of Green Roofs
FRF is located at NRC-IRC’s Montreal Road Campus, Ottawa
FRF
Field Roofing Facility
Weather Station
Green Roof
Reference Roof
Field Roofing Facility
8 m (2
6 ft.)
9 m (30 ft.)
5 m
(16
ft.)
N
Green RoofReference Roof
Parapet1 m (3 ft.)
Field Roofing Facility
Drainage layerFilter membraneGrowing medium
Vegetation
Structural supportVapour control layer
Thermal insulationSupport panel
Reference Roof Green Roof
VB
IN
INS
SB
Layer
SM
Thermocouple
OUT
MEM
Heat Flux Transducer
Roof membrane
Principal Components and Sensor Locations
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Green RoofReference Roof
A typical sunny summer day
IN
MEM
OUT
Temperature Profile
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Temperature Profile
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Green Roof
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Heat Flow Comparison
Green RoofReference Roof
Heat loss Heat lossHeat Loss
Heat gain
Heat gain
A typical sunny summer day
Average Daily Heat Flow Through Roof Surfaces(observations during year 1 and year 2)
7.0 6.8
5.2
6.96.4
6.86.8
2.6
0.8
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6.0
3.3
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6.6
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Winter 01 Spring 01 Summer 01 Fall 01 Winter 02 Spring 02 Summer 02
Hea
t Flo
w (k
Wh/
day)
Average Daily Heat Flow Through Roof Surfaces(First 2 years of observation)
Reference Roof Green Roof
Heat Flow Comparison
Rooftop Microclimate -Instrumentation
Rooftop Microclimate -Instrumentation
Green RoofReference Roof Close up
Rooftop Microclimate
50mm (2 in.)100mm (4 in.)
200mm (8 in.)
300mm (12 in.)
600mm (24 in.) RH/T sensor inradiation shield
RH/T sensor inradiation shield
Solar radiation sensor
Thermocouples
Solar Reflectance
020602, Solar Radiation
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nsity
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Garden
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Comparison of Solar Reflectance of Roof Surfaces
Green
Reference
Sun
Rooftop Temperature at Different Levels
020916, MC-Reference
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020916, MC-Garden
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Green RoofReference Roof
Rooftop Temperature
50mm (2 in.)100mm (4 in.)
200mm (8 in.)
300mm (12 in.)
600mm (24 in.) 25°C
26°C
28°C
32°C
37°C
25°C
23°C
25°C
28°C
27°C
Reference Roof Green Roof
Measured at noon on a typical summer day
Summary
Energy Efficiency– Green roofs can reduce the heat flow between the building and its
environment and lower the energy demand.
– Green roofs are more energy efficient in the summer than in the winter.
– Based on field data in Ottawa, the green roof reduced the heat flow through the roof by about 110 MJ/m2/year.
Urban Heat Island– Green roofs lower the temperature of the surface air 100 mm
(4 in.) above the roof surface by as much as 6°C (11°F).
– The green roof lowered the air temperature up to 200 mm (8 in.) above the roof surface.
Thank You!
Karen Liu
Research Officer
National Research Council
Tel: 613-993-4584
Fax: 613-954-5984
E-mail: [email protected]
