This study examined the impacts of insulation strategy and membrane colour on conventional roof performance in Canada. It monitored 9 roof sections with different colour membranes (white, grey, black) and insulation types (stone wool, polyiso, hybrid). Field monitoring found that darker membranes experienced much higher temperatures than lighter ones. Insulation type also impacted temperatures, with stone wool and hybrid strategies showing less peak heating and cooling than polyiso alone. Energy modeling further showed that lighter membranes and stone wool or hybrid insulation led to lower energy use. The study aims to continue monitoring insulation movement, moisture, and aging effects over the long term.

1. Conventional Roofs: Measuring
Impacts of Insulation Strategy
and Membrane Colour in Canada
LORNE RICKETTS, MASC
RDH BUILDING ENGINEERING LTD. VANCOUVER, BC
CO-AUTHORS: GRAHAM FINCH, MASC, P.ENG. & MARCUS DELL, MASC P.ENG.

2. Outline
à Introduction & Background
à What prompted the study?
à Study of Conventional Roof Performance
à Laboratory Testing
à Field Monitoring
à Energy Modelling
à Conclusions & Areas of Continuing Research

3. Conventional Roofing Recap
à Most common low-slope roof in North America
à Air barrier and vapour control layer below
insulation on top of structure, then insulation,
then membrane on top
à Insulation typically foam plastic (polyiso, EPS),
mineral fibre also used
à Roof slope typically achieved by tapered
insulation unless structure is sloped
à Roof membrane exposed to temperature, UV,
traffic – needs to be durable
à Attachment of membrane/insulation can be
adhered, mechanically attached, loose laid
ballasted, or combination

4. Polyiso Shrinkage
Ridged Membrane
Insulation Issues
à Long-term shrinkage
à Thermal expansion/contraction
What Prompted the Study?
XPS Expansion
EPS Shrinkage

5. What Prompted the Study?
Cover Board Issues
à Delamination & fungal growth
Wood fiberboard cover-board
wetting and delamination
Wetting & resulting fungal growth on
gypsum cover board

6. What Prompted the Study
The Great Colo(u)r Debate
à Darker Colours (more absorptive, less reflective)
à Higher temperatures, more movement and
membrane stress, higher cooling loads, lower
heating loads
à Lighter Colours (less absorptive, more reflective)
à Lower temperatures, less movement and
membrane stress, lower cooling loads, higher
heating loads
à LEED points for use of highly
reflective roofs regardless of energy
implication and local climate
à Balance needed between membrane
durability, assembly movement,
heating and cooling loads
Confused owner?
New 5 Years Old

7. Study of Conventional Roof
Performance

8. Guiding Purpose of the Study – Why?
à Quantify performance of different colours of exposed roof membrane
à White, Grey, & Black
à Quantify performance of different insulation types
à Stone wool, Polyiso, & Hybrid
à Quantify combined impact of membrane colour and insulation
à Observe impact of the long-term soiling of white SBS cap sheets
à Monitor long-term shrinkage/movement of insulation and relative
humidity/moisture levels within insulation
à Laboratory testing of material properties

9. Roof Membrane Colours
à 3 different 2-ply SBS roof
membrane cap sheet colours
(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

10. 3 Different Insulation Strategies
Stone wool - R-21.4
(2.5” + 3.25”, adhered)
Weight: 26.7 kg/m2
Heat Capacity: 22.7 kJ/K/m2
Polyiso - R-21.5
(2.0” + 1.5”, adhered)
Weight: 4.6 kg/m2
Heat Capacity: 6.8 kJ/K/m2
Hybrid - R-21.3
(2.5” Stone wool + 2.0” Polyiso, adhered)
Weight 14.3 kg/m2, Heat Capacity – 13.7 kJ/K/m2
Design target: Each Assembly the same ~R-21.5 nominal

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

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

13. Laboratory Testing of
Insulation Performance

14. Laboratory Testing of Insulation R-values
à 3rd Party ASTM C518 thermal
transmission material testing
à Polyiso and stone wool
insulation removed from site & 4
year old polyiso samples from
prior study

15. Laboratory Testing of Project Insulation
3.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
7.0
-­‐10 0 10 20 30 40 50
R-­‐value
per
inch
Mean
Temperature
of
Insulation
[°C]
Installed
&
Aged
Insulation
R-­‐values
-­‐ Based
on
Mean
Temperature
Polyiso
-­‐
Maximum Polyiso
-­‐
Average Polyiso
-­‐
Minimum
Polyiso
-­‐
Aged
(4
years) Stone
Wool
-­‐
Average

16. 14
15
16
17
18
19
20
21
22
23
24
-­‐10 0 10 20 30 40 50 60
Effective
Assembly
R-­‐value
Outdoor
Membrane
Surface
Temperature
(Indoor,
21oC)
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)
Varying R-value of Field Roof Assemblies

17. Field Monitoring Findings

18. Study Findings: What is the
Impact of Membrane Colour?

19. 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.
Colour – Impact on Surface Temperatures
à Increased temperatures affect:
à Membrane degradation/durability
à Heat/Energy Flow through assembly

20. Study Findings: What is the
impact of insulation arrangement?

21. Insulation Impact on Peak & Lagging
Membrane & Metal Deck Temperatures
RoofMembraneMetalDeck

22. 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
Heat
Flux
[W/m²]
Heat
Flux
Sensors
G-­‐ISO
HF
G-­‐ISO-­‐SW
HF
G-­‐SW
HF

23. 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
Degree
Days
[°C·∙days]
Daily
Energy
Transfer
[W·∙hr/m²
per
day]
Monthly
Average
Daily
Energy
Transfer
by
Insulation
Arrangement
ISO ISO-­‐SW SW Heating
Degree
Days
(18°C)
OutwardHeat
FlowInwardHeat
Flow
1 W/m2 = 0.32 Btu/hr·ft2
Outward
HeatFlow
Inward
HeatFlow

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

25. Impact of Membrane Colour and
Insulation Strategy on Energy
Consumption

26. Energy Consumption and Membrane/
Insulation Design
à Energy modeling performed for a
commercial retail building (ASHRAE
building prototype template) to compare
roof membrane colour & insulation strategy
à Included more realistic thermal performance of
insulation into energy models
à Stone wool: Lower R-value/inch
Higher heat capacity and mass
à Polyiso: Higher R-value/inch
(varies with temperature a lot)
Lower heat capacity
Lower mass
à Hybrid: Moderates temperature extremes
of polyiso – makes polyiso
perform better

27. 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

28. Conclusions & Continuing Research
à Aging and temperature have significant effects on the thermal performance
of insulation – all types affected to varying degrees
à Effective insulation R-values, thermal mass, latent heat transfer, membrane
colo(u)r all impact membrane temperatures and heat flows
à Effects building energy consumption and membrane durability
Rated R-values of insulation do not tell the whole
story about actual heat flow through roofs.
à 2 years so far, but study is ongoing
à Soiling, long-term movements, aging etc.
à Confirm impacts of moisture movement within the assemblies

29. à rdh.com
Questions
LORNE RICKETTS, MASC, EIT
LRICKETTS@RDH.COM – 604-873-1181