The document summarizes a study that monitored the performance of different roofing membrane colors (white, gray, black) and insulation strategies (stone wool, polyiso, hybrid) over two years. Key findings include: 1) Darker membrane colors experienced significantly higher surface temperatures, while lighter colors provided better heat reflection and energy efficiency. 2) The insulation strategy had a major impact on peak and lagging membrane and deck temperatures, with stone wool and hybrid configurations performing best. 3) Insulation type also influenced heat loss and gain, with stone wool and hybrid assemblies showing less heat transfer.

1. Conventional Roofing Assemblies:
Measured Benefits of Light to Dark Roofing
Membranes & Alternate Insulation Strategies
PHILADELPHIA BEC – SEPTEMBER 16 2014
GRAHAM FINCH, MASc., P.ENG – PRINCIPAL, BUILDING SCIENCE RESEARCH SPECIALIST

2. “RDH Building Sciences” is a Registered Provider with The
American Institute of Architects Continuing Education
Systems (AIA/CES). Credit(s) earned on completion of this
program will be reported to AIA/CES for AIA members.
Certificates of Completion for both AIA members and non-AIA
members are available upon request.
This program is registered with AIA/CES for continuing
professional education. As such, it does not include content
that may be deemed or construed to be an approval or
endorsement by the AIA of any material of construction or any
method or manner of handling, using, distributing, or dealing
in any material or product.
Questions related to specific materials, methods, and services
will be addressed at the conclusion of this presentation.

3. Copyright Materials
This presentation is protected by US and
International Copyright laws. Reproduction,
distribution, display and use of the
presentation without written permission of
the speaker is prohibited.

4. Learning Objectives
At the end of this program, participants will be able to:
1. Understand how to evaluate and select an appropriate conventional
roof membrane type and color for various climate zones
2. Understand how to evaluate and design the most appropriate
insulation strategy for a conventional roof. Learn how different
insulation materials and hybrid insulation combinations will behave
differently in-service and have a varying effective R-value depending
on temperature.
3. Understand how different insulation strategies and roofing
membranes affect heating and cooling energy consumption in
different building types.
4. Observe case studies where recommended roofing membrane and
insulation designs have been implemented.

5. Presentation Outline
 Conventional Roofing Designs and Current Issues
 Conventional Roofing Field Monitoring and
Research Program
 Field Results – Membrane & Insulation Strategies
 Selecting Optimum Roofing Color and Insulation
Strategy for Energy Efficiency
 Case Studies

6. Conventional Roofing Designs &
Current Issues

7. Recap: Conventional Insulated Roofs
 Most common low-slope roof application in North
America
 Insulation installed above structure, protected by
roofing membrane - Insulation is typically foam plastic
(polyiso, EPS), though mineral fiber also used
 Roofing membrane is exposed to temperature, UV,
traffic – needs to be durable
 Roof slope typically achieved by tapered insulation
unless the structure is sloped
 Attachment of membrane/insulation can be: adhered,
mechanically attached, loose laid ballasted, or
combination to resist wind uplift
 Wood, concrete, or steel structure substrate
 Air barrier and vapour control layer below insulation on
top of structure (depending on climate/design)

8. Current Issues With Conventional Roofs
 Roofing membrane issues
 Insulation movement – Thermally induced
 Causes membrane ridging and stresses
 More movement with thicker amounts of insulation (becoming more
common) and certain insulation types
 More movement in roofs with darker colored membranes
 Insulation movement - Long term shrinkage, expansion, contraction
 Gaps between insulation boards, induced membrane stresses
 Cover board /protection board failure – delamination, softening, organic
growth, fastener corrosion
 Moisture trapped in insulation and roof assembly from wetting
during construction or from small leaks in-service
 Becoming more common to install leak detection monitoring within
conventional roofs and find this out – what to do about it? How to adjust
monitoring?

9. Membrane Ridging & Insulation Movement
TPO over gypsum board
and polyiso
SBS over wood fiberboard and XPS

10. Membrane Ridging & Insulation Movement
2 ply SBS over Fiberboard & XPS

11. Insulation Movement & Membrane Failure
2 ply SBS over EPS

12. Insulation Movement & Membrane Failure
2 ply SBS over Polyiso over EPS
taper package

13. Wood Fiberboard Coverboard Issues
Wood fiberboard cover-board
wetting and delamination

14. Cover Board Failures & Membrane Delamination

15. Gypsum Cover Board Issues
Wetting, Softening & Facer delamination
Wetting & Fungal growth Wetting & accelerated fastener corrosion

16. Insulation Shrinkage & Heat Loss
2 ply SBS over single layer of mechanically attached Polyiso

17. Insulation Shrinkage Study
 Polyiso has had a reported history of board shrinkage –
both initial and long-term
 Related to manufacturer, mix, temperature, moisture, and age
 Results in gaps between the insulation boards and induces
stresses introduced into roof membranes
 Past monitoring shows varying amounts of ongoing
shrinkage – primarily influenced by age of product when
installed

18. Polyiso Shrinkage Monitoring Study
 Year 1 – 0.2% (2 mm in 1200 mm)
Shrinkage-mm
20102009
0
2
1
3 1/8”

19. Polyiso Shrinkage Monitoring Study
 Year 4 – 0.2% to 0.7% (2-8 mm in 1200 mm)
Shrinkage-mm
8
0
2
4
6
2009 2013
Year 1
1/4”

20. Roof Membrane Color Considerations
 Roof membrane or ballast color (solar absorptivity)
influences surface temperature
 Darker colors (more absorptive, less reflective)
results in higher temperatures, more assembly
movement and membrane stress, higher cooling
loads, lower heating loads
 Lighter colors (less absorptive, more reflective)
results in lower temperatures, less assembly
movement and membrane stress, lower cooling
loads, higher heating loads
 Balance needed between membrane durability,
assembly movement, heating and cooling loads
 Programs such as LEED have points for use of highly
reflective roofs regardless of energy implication and
local climate.
 Long term impacts and soiling of light colored roofs

21. Membrane Soiling – 5 years, Poor Slope TPO

22. Conventional Roofing Field
Monitoring Study

23. Guiding Purpose of the Study – Why?
 Quantify performance of different colors of exposed roof membrane
(white, grey, black)
 What impact does LEED have on roof energy performance
 Quantify performance differences of different insulation types:
stone wool, polyiso and hybrid insulation combinations
 Quantify combined impact of membrane color and insulation strategy
 Observe impact of the long-term soiling of white SBS cap sheets
 Monitor long-term shrinkage/movement of insulation and relative
humidity/moisture levels within insulation
 Laboratory testing of material properties we didn’t know
 While Certain materials used for Phase 1 of study – key findings are
applicable to all membrane & insulation types

24. Roof Membrane Colors
 3 different 2-ply SBS roof
membrane cap sheet
colors (white reflective,
grey, black)
White Reflective Cap Sheet:
SRI 70, Reflectance 0.58, Emittance 0.91
Grey Cap Sheet:
SRI 9, Reflectance 0.14, Emittance 0.85
Black Cap Sheet:
SRI -4, Reflectance 0.04, Emittance 0.85

25. 3 Different Insulation Strategies
Stone wool - R-21.4
(2.5” + 3.25”, adhered)
Polyiso - R-21.5
(2.0” + 1.5”, adhered)
Hybrid - R-21.3
(2.5” Stone wool + 2.0” Polyiso, adhered)
Design target: Each Assembly the same ~R-21.5 nominal

26. Insulation and Cap Sheet Layout
 9 unique roof test areas, each 40’ x 40’ and each behaving
independently
 Similar indoor conditions (room temperature) and building use
(warehouse storage)
 Climate Zone 4
Polyiso
Hybrid
Stone wool
120’
120’
Grey
White
Black
Polyiso
Hybrid
Stonewool

27. Sensor Selection and Installation
 Temperature
 Heat Flux
 Relative Humidity
 Moisture Detection
 Displacement
 Solar Radiation
Heat Flux Relative Humidity &
Moisture Detection
Displacement
Temperature Solar Radiation

28. Sensor Positioning
T - Temperature
RH - Relative Humidity
HF - Heat Flux
M - Displacement
M
M

29. Roof and Sensor Installation

30. Roof and Sensor Installation

31. Roof and Sensor Installation

32. Measured Insulation
Performance

33. My Most Common Designer Question Lately:
What R-value is My Insulation?

34. Laboratory Testing of Insulation R-values
 3rd
Party ASTM C518 thermal transmission
material testing performed as part of
monitoring study
 Polyiso and stone wool insulation
removed from site + aged 4 year old
polyiso samples from prior research
study
 Wanted to know actual R-value as
installed and temperature impacts to
calibrate sensors
 Testing performed at mean insulation
temperatures from 25, 40, 75, and 110°F to
develop R-value vs temperature

35. Laboratory Testing of Project Insulation
3.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
7.0
20 40 60 80 100 120
R-valueperinch-IPUnits
Mean Temperature of Insulation - °F
Installed & Aged Insulation R-values per Inch - Based on Mean Temperature (°F)
Polyiso - Maximum Polyiso - Average Polyiso - Minimum
Polyiso - Aged (4 years) Stone Wool - Average

36. Applying Laboratory Testing to the Field
 Design R-values for each assembly ~R-21.5
Stone Wool -2.5” + 3.25”, Weight 26.7 kg/m2
,
Heat Capacity – 22.7 kJ/K/m2
Polyiso - 2.0” + 1.5”, Weight 4.6 kg/m
Heat Capacity – 6.8 kJ/K/m2
Hybrid – 2.5” Stone wool over 2.0” Polyiso,
Weight 14.3 kg/m2
, Heat Capacity – 13.7 kJ/K/m2

37. Varying R-value of Field Roof Assemblies
14
15
16
17
18
19
20
21
22
23
24
10 20 30 40 50 60 70 80 90 100 110 120 130 140
EffectiveAssemblyR-value-IPUnits
Outdoor Membrane Surface Temperature (Indoor, 72°F)
Effective Roof Insulation R-value - Based on Roof Membrane Temperature
Stone Wool (Initial or Aged)
Hybrid (Initial Average)
Hybrid (Aged)
Polyiso (Initial Average)
Polyiso (Aged)

38. Field Monitoring Findings

39. Field Monitoring Results
 Monitoring from first 2
years shown today
 Plan to monitor for 5
years for long-term
trends and aging effects
 Data shown here to
demonstrate:
1. Impact of Membrane
Color
2. Impact of Insulation
Strategy
3. Combined Impacts
SENSOR CODING:
W – white
G – grey
B – black
SW - stone wool
ISO – polyiso
ISO-SW – hybrid

40. Study Findings: How Big of a
Difference does Membrane
Color Have?

41. White Membrane Soiling & Reflectance
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
May Jun Jul Aug Sept Oct Nov Dec Jan Feb Mar Apr Annual Rated
Reflectance
Reflectance of Membranes
White (high) White (low) Grey
*
*Rated reflectance was measured using a different method than was used in the field study.

42. 32
50
68
86
104
122
140
158
176
194
0
10
20
30
40
50
60
70
80
90
May Jun Jul Aug Sept Oct Nov Dec Jan Feb Mar Apr
Temperature[°F]
Temperature[°C]
Monthly Average of Daily Maximum Membrane Temperatures and Maximum Membrane
Temperature for Each Month by Membrane Colour
White Grey Black White - Maximum Grey - Maximum Black - Maximum
* *
*W-ISO-SW had significant data loss in August and September and is removed from the average for those months.
Color – Impact on Surface Temperatures

43. Color - Differences in Net Heat Flow
-200
-150
-100
-50
0
50
100
May Jun Jul Aug Sept Oct Nov Dec Jan Feb Mar Apr Annual
DailyEnergyTransfer[W·hr/m²perday]
Monthly Average Daily Energy Transfer by Membrane Colour
White Grey Black
Outward
HeatFlow
Inward
HeatFlow
Monthly Average Daily Energy Transfer by Membrane Color

44. Color & Calculated Degradation
 Relative degradation rate calculated from measured cap sheet
temperatures
 Further study needed to quantify age and physical property
effects
Black roof with stone wool directly below
the membrane doesn’t get as hot

45. Study Findings: How Big of a
Difference does the Insulation
Strategy Have?

46. Insulation Impact on Peak & Lagging
Membrane & Metal Deck Temperatures
RoofMembraneMetalDeck
0
10
20
30
40
50
60
70
80
90
Jun 30 0:00 Jun 30 6:00 Jun 30 12:00 Jun 30 18:00 Jul 1 0:00
Temperature[°C]
Roof Membrane Cap Sheet Temperatures
W-ISO T-CAP
W-ISO-SW T-CAP
W-SW T-CAP
G-ISO T-CAP
G-ISO-SW T-CAP
G-SW T-CAP
B-ISO T-CAP
B-ISO-SW T-CAP
B-SW T-CAP
Outdoor-T
24
26
28
30
32
34
36
Jun 30 0:00 Jun 30 6:00 Jun 30 12:00 Jun 30 18:00 Jul 1 0:00
Temperature[°C]
Metal Deck Temperatures
W-ISO TEMP-DECK
W-ISO-SW TEMP-DECK
W-SW TEMP-DECK
G-ISO TEMP-DECK
G-ISO-SW TEMP-DECK
G-SW TEMP-DECK
B-ISO TEMP-DECK
B-ISO-SW TEMP-DECK
B-SW TEMP-DECK
176°F
140°F
104°F
68°F
97°F
75°F
86°F

47. Heat Flux Data – Heat Loss vs Gain
-30
-25
-20
-15
-10
-5
0
5
10
15
Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar
HeatFlux[W/m²]
Heat Flux Sensors
W-ISO HF
W-ISO-SW HF
W-SW HF
G-ISO HF
G-ISO-SW HF
G-SW HF
B-ISO HF
B-ISO-SW HF
B-SW HF
SENSOR CODING: W – white, G – grey, B - black
SW - stone wool, ISO – polyiso, ISO-SW - hybrid
Heat
Loss
Heat
Gain
1 W/m2
=
0.32 Btu/hr/ft2

48. Heat Flow – Heat Loss vs Heat Gain
Winter vs. Summer
-25
-20
-15
-10
-5
0
5
10
Feb 21 Feb 22 Feb 23
HeatFlux[W/m²]
Heat Flux Sensors
W-ISO HF
W-ISO-SW HF
W-SW HF
G-ISO HF
G-ISO-SW HF
G-SW HF
B-ISO HF
B-ISO-SW HF
B-SW HF
-25
-20
-15
-10
-5
0
5
10
Jun 30 Jul 1 Jul 2
HeatFlux[W/m²]
Heat Flux
l 2
Flux Sensors
W-ISO HF
W-ISO-SW HF
W-SW HF
G-ISO HF
G-ISO-SW HF
G-SW HF
B-ISO HF
B-ISO-SW HF
B-SW HF
W- white, G-grey, B-black, SW-stone wool, ISO - polyiso
Heat Loss Heat Gain

49. Heat Flow – Variation with Insulation Strategy
-25
-20
-15
-10
-5
0
5
10
Jun 30 0:00 Jun 30 6:00 Jun 30 12:00 Jun 30 18:00 Jul 1 0:00
HeatFlux[W/m²]
Heat Flux Sensors
W-ISO HF
W-ISO-SW HF
W-SW HF
B-ISO HF
B-ISO-SW HF
B-SW HF
Heat
Loss
Heat
Gain
SENSOR CODING: W – white, B - black
SW - stone wool, ISO – polyiso, ISO-SW - hybrid

50. Heat Flow – Variation with Insulation Strategy
SENSOR CODING:
SW - stone wool, ISO – polyiso, ISO-SW - hybrid
-25
-20
-15
-10
-5
0
5
10
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
HeatFlux[W/m²]
Heat Flux Sensors
G-ISO HF
G-ISO-SW HF
G-SW HF

51. Net Annual Impact of Insulation Strategy
0
100
200
300
400
500
600
-150
-100
-50
0
50
100
May Jun Jul Aug Sept Oct Nov Dec Jan Feb Mar Apr Annual
DegreeDays[°C·days]
DailyEnergyTransfer[W·hr/m²perday]
Monthly Average Daily Energy Transfer by Insulation Arrangement
ISO ISO-SW SW Heating Degree Days (18°C)
OutwardHeatFlowInwardHeatFlow
1 W/m2
= 0.32 Btu/hr∙ft2

52. Other Findings to Date
 Insulation Movement monitoring ongoing
 Observing daily insulation swings
 Seeing some long-term movement of
insulation, but also movement of metal deck
structure interfering with long-term data
 Relative Humidity and moisture movement
ongoing
 Seeing harmless seasonal movement of built-
in water vapor through insulation
 Water vapor also moves energy – latent heat
 Cut-tests confirm roofs all dry and no issues

53. Optimizing Membrane Color and
Insulation Strategy for Energy
Efficiency

54. Energy Consumption and Membrane/
Insulation Design
 Calibrated energy modeling used to compare roof
membrane color/solar absorptivity & insulation strategy
 White, Grey or Black Roof Membrane
 Polyiso, Stone wool, or Hybrid insulation approach
• Stone wool has lower R-value/inch but higher heat
capacity and higher mass
• Polyiso has a higher R-value/inch (varies with temperature)
and has a lower heat capacity and lower mass
• Hybrid approach has stone wool over top of polyiso which
moderates temperature extremes of polyiso insulation –
makes polyiso perform better

55. Energy Consumption and Membrane/Insulation
Design
 Energy modeling performed for a
commercial retail building
(ASHRAE building prototype
template)
 Results calibrated with
temperature/heat-flux data from
monitoring study
 Input temperature dependant &
aged R-values into energy model –
base R-20 roofs
 Help to select the optimum
insulation and membrane color
combination for energy efficiency

56. Energy Modeling of Temperature Dependant
Insulation R-values
 Input lab measured temperature dependant insulation R-value for polyiso and
stone wool into energy model
 Heating energy for Climate Zone 4 (Vancouver) shown here, R-20 insulation
 Impact is significant enough that should be accounted for
 Results in different design rankings of lowest to highest energy consumption
36
37
38
39
40
41
42
43
44
Dark Roof Gray Roof White Roof
AnnualHeatingEnergyConsumption,
kWh/m2
Model Default - Constant Conductivity
Polyiso
Stone wool
Hybrid
36
37
38
39
40
41
42
43
44
Dark Roof Gray Roof White Roof
AnnualHeatingEnergyConsumption,
kWh/m2
Revised Model - Temperature
Dependent Conductivity
Polyiso
Stone Wool
Hybrid
Total Energy Consumption includes walls, windows, air leakage, slab on grade, +roof

57. 0
10
20
30
40
Black Roof Gray Roof White Roof
AnnualHeatingEnergyConsumption,
kWh/m2
Polyiso
Stone Wool
Hybrid
Aged Polyiso
Aged Hybrid
Most Energy Efficient Roofing Combination in
Philadelphia Region – Climate Zone 4
0
10
20
30
40
Black Roof Gray Roof White Roof
AnnualCoolingEnergyConsumption,
kWh/m2
Polyiso
Stone Wool
Hybrid
Aged Polyiso
Aged Hybrid
0
10
20
30
40
Black Roof Gray Roof White Roof
AnnualSpace-ConditioningConsumption,
kWh/m2
Polyiso
Stone Wool
Hybrid
Aged Polyiso
Aged Hybrid
Lower is Better – Total Energy Includes Loss through Roofs + Walls,
Floor, Windows, Air Leakage etc.
12 kBtu/ft2
/yr

58. Most Energy Efficient Roofing Combination?
0
20
40
60
80
100
120
1 - Miami 2 - Houston 3 - San Francisco 4 - Baltimore 5 - Vancouver 6 - Burlington VT 7 - Duluth 8 - Fairbanks
AnnualHeatingEnergy,kWh/m2
Climate Zone
Black - Aged Polyiso
Black - Stonewool
Black - Aged Hybrid
White - Aged Polyiso
White - Stonewool
White - Aged Hybrid
0
20
40
60
80
100
120
1 - Miami 2 - Houston 3 - San Francisco 4 - Baltimore 5 - Vancouver 6 - Burlington VT 7 - Duluth 8 - Fairbanks
AnnualCoolingEnergy,kWh/m2
Climate Zone
Black - Aged Polyiso
Black - Stonewool
Black - Aged Hybrid
White - Aged Polyiso
White - Stonewool
White - Aged Hybrid
Commercial Retail Building Heating Energy – kWh/m2
/yr
Commercial Retail Building Cooling Energy – kWh/m2
/yr

59. Most Energy Efficient Roofing Combination?
Lighter membrane, stone
wool or hybrid is better for
same design R-value
Darker membrane, stone
wool or hybrid is better
for same design R-value

60. Summary – Key Points
 Research and Field Monitoring Study Findings
 Design R-value may change in service – all types of insulation are
affected to varying degrees – Is not Static
 In addition to design R-value - heat capacity and latent moisture
transfer within insulation has an impact on temperatures and
energy transfer
 Optimization of heating and cooling based on roof membrane
color and insulation strategy suggested
 Careful selection of insulation strategy and membrane color will
have a positive impact on roof assembly performance

61. Case Studies

62. Stone Wool Insulation in Conventional Roofing
 R-value of stone wool is R-3.7/inch
compared to a R-4 to R-6/inch for
polyiso and R-4/inch for EPS
 Need thicker stone wool to achieve same
R-value as polyiso in design
 If polyiso kept closer to indoor
temperatures, then it has a higher
effective R/inch (closer to LTTR)
 Insulate the Polyiso!
 Hybrid insulation provides good blend
of material properties and economics
 Tapered insulation packages available:
EPS, Polyiso, or Stone wool

63. Case Study 1 - High-rise Re-Roof
Assembly: 2-ply SBS torched to 2” asphalt impregnated stone wool
over 2” polyiso (adhered)

64. Case Study 2 – Residential Re-Roof
Assembly: 2-ply SBS torched to 2” asphalt impregnated stone wool, over 2”
polyiso, over polyiso tapered package (mechanically attached)

65. Case Study 3 – Heritage Re-Roof
Assembly: 2-ply SBS torched to 1” stone wool asphalt impregnated cover board
adhered to 2” stone wool, mechanically fastened through EPS taper package

66. Case Study 4 – New Roof over First Tallest
Wood Structure in North America
Design & Architectural Renders: Michael Green Architecture (MGA)

67. Case Study 4 – New Roof over First Tallest
Wood Structure in North America
R-40+ Conventional Roof Assembly – 2 ply SBS, 4” Stonewool, 4” Polyiso, Protection
board, Tapered EPS (0-8”), Torch applied Air/Vapor Barrier(Temporary Roof),
¾” Plywood, Ventilated Space (To Indoors), CLT Roof Panel Structure (Intermittent)

68. Case Study 4 – New Roof over First Tallest
Wood Structure in North America

69. Case Study 5 – What Would RDH Do?

70. Designer and Roofing Contractor Feedback
 Stone wool insulation relatively easy and fast to install. Heavier than
EPS/polyiso boards, but doesn’t blow away
 Stone wool insulation lays flat and takes up uneven surfaces, tight
board installation, very few gaps compared to more rigid foam
boards
 Stone wool is softer than polyiso and potentially softens during
construction from foot traffic – not issue in open field areas, but
compression can occur in high traffic areas prior to covering
 Typically address with extra asphalt protection board overlay.
 Thicker insulation build-up for stone wool compared to polyiso due to
R-value differences, may be an issue where thickness is at a premium
or could be issue during re-roof around existing doors and curbs etc.
 Watch mechanical fasteners without a protection board.
 Adhesive with stone wool must be applied and set-in quickly before
foam expands. Slightly different process than with EPS/polyiso.

71. Recommended Conventional Roofing Strategies
for Energy & Durability
 Design to provide good balance of cost,
thickness, & performance (energy,
durability, membrane life)
 Roof Membrane – grey or other neutral
color for northern climates, light in south
 Adhered system with stone wool
insulation as top layer / cover board (30-
50% of total insulation R-value)
 Layer of polyiso (below staggered) joints
with taper package
 Self adhered/torched sheet air/vapour
barrier membrane (temporary roof) over
substrate
 Adhered layers preferred instead of
mechanically attached, where possible to
balance cost

72. This concludes The American Institute of
Architects Continuing Education Systems Course
Graham Finch
Dipl.T, MASc, P.Eng
RDH Building Sciences Inc.
gfinch@rdhbe.com

73.  rdhbe.com
Discussion + Questions
Graham Finch – gfinch@rdhbe.com – 604 873 1181