The thermal expansion and contraction of insulation products within conventional roof assemblies has been identified as a potential performance concern in the roofing industry. This movement can create gaps between insulation boards, which can short-circuit the insulation with respect to heat flow, and in conventional roof assemblies where the insulation also provides the substrate for the roofing membrane, insulation movement can also adversely affect the durability and integrity of the membrane and roofing system. Problems with creasing and ridging of membranes have been observed in the field, along with stress concentrations and holes around fixed penetrations. In particular, field observations have indicated that shrinkage of expanded polystyrene (EPS) insulation products may put undue stress on the roof membranes and could potentially affect the durability of styrene-butadiene-styrene (SBS) roof membranes. To investigate these industry concerns regarding the potential effect of dimensional movement of EPS insulation on the performance of SBS membranes, laboratory testing was performed on conventional roof specimens in a purpose-built climate chamber. The roof assemblies were cooled and heated to evaluate the amount of insulation movement, and to then observe the impact of these temperature cycles on the roof assembly. This portion of the investigation in to this issue focused on recreation of the observed field condition (e.g., wrinkled membrane), and direct comparison of the relative performance of different insulation types as a first step towards determining the cause of the observed in-service wrinkling. Presented at the 15th Canadian Conference on Building Science and Technology.

1. 1
Impact of Insulation Dimensional
Stability on Conventional Roofs
2017 CCBST Conference – Day 3
November 8th, 2017
Presented by: Lorne Ricketts | MASc, P.Eng.
Co-Author: Jun Tatara | Dipl.T.

2. 2
 Introduction & Background
 Laboratory Testing
 Methodology
 Findings
 Conclusion & Next Step
Presentation Outline

3. 3
Introduction & Background

4. 4
Introduction & Background

5. 5
Introduction & Background

6. 6
Introduction & Background
 Thermal expansion and contraction of insulation products
within conventional roof assemblies has been identified as a
potential performance concern in the roofing industry

7. 7
Laboratory Testing Overview
 Insulation and SBS membrane material testing
 Laboratory testing using purpose-built climate chamber
 Can we recreate the wrinkles?
› Attempt to reproduce the creasing observed in the field
 What parameters impact the occurrence of wrinkles?
› Dimensional movement of insulation within the assembly
› Asphaltic and Fibreboard Cover Boards

8. 8
Insulation Material Testing
 EPS insulation found to expand up to ~80°C,
then contraced rapidly between 80-90°C
-4°F 14°F 32°F 50°F 68°F 86°F 104°F 122°F 140°F 158°F 176°F 194°F 212°F
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0.6%
0.8%
-20°C -10°C 0°C 10°C 20°C 30°C 40°C 50°C 60°C 70°C 80°C 90°C 100°C
ChangeinDimensionof48"Board[inches]
%ChangeinDimension
Polyiso
EPS
XPS
Stone Wool

9. 9
Methodology – Roof Specimen
 2-ply conventional roof roughly 4' x 8' with 4" of insulation
 Continuous joint in the middle of the insulation layer
perpendicular to the length of the specimen
 Cover board and roof membrane were installed continuously
across the insulation joint
 Constructed by a certified roofer familiar with roofing
products and installation techniques
Ribbon-adhered specimen in the process of
attaching cover board to SW insulation
Schematic drawing of roof specimen showing
insulation layout with central joint between insulation
boards (EPS roof specimen shown)

10. 10
Methodology – Roof Specimen
 Total of 5 roof specimens were tested
Cover board¹: 4.8 mm (3/16“), glass mat-reinforced asphaltic cover board
Cover board²: 12.7 mm (1/2") high density fire-resistant fiberboard
Cover Board¹
(Mechanically
Fastened)
Cover Board¹
(Ribbon-Adhered)
Cover Board¹
(Mechanically
Fastened)
Cover Board²
(Mechanically
Fastened)
Cover Board¹
(Ribbon-Adhered)
4" EPS 4" EPS 4" Stone Wool 4" EPS 4" Stone Wool
Interior
Roof 1 Roof 2 Roof 3
Self-Adhered Vapour Barrier
1/2" Plywood
SBS Cap Sheet (Non-Woven Polyester Reinforced)
SBS Base Sheet (Non-Woven Polyester Reinforced)
Roof 4 Roof 5
Exterior
Insulation Type for
Mechanically
Fastened
Insulation Type for
Ribbon-Adhered
Cover Board Type

11. 11
Methodology – Climate Chamber
 RDH’s purpose-built climate
chamber
 Roof specimens were
exposed to both cold (-15°C)
and hot (90°C) temperatures
while monitoring
performance characteristics
such as dimensional
movement and force
exerted by roof specimen

12. 12
Methodology – Climate Chamber

13. 13
Methodology – Displacement Sensors
 Insulation Movement
 One of the key
measurements was taken
with displacement sensors
installed between
insulation boards
 Displacement sensors
were embedded in the
insulation

14. 14
Methodology
 What makes a wrinkle?
 Important to note that to make a wrinkle some kind of differential
movement or fixation is typically required.
 Unlikely that a membrane wrinkles in the field all on its own
 This is a problem involving the interaction of multiple
components and factors
An example of insulation contraction/shrinkage
widening the gap.

15. 15
0
10
20
30
40
50
60
70
80
90
12:00 AM 4:00 AM 8:00 AM 12:00 PM 4:00 PM 8:00 PM 12:00 AM
Temperature(°C)
SBS Surface Above Insulation Under Insulation Interior Air
Methodology – Test Procedure
 Uniform Cooling and Heating
 Create a worst-case temperature conditions to highlight
performance of each roof arrangement

16. 16
Can we recreate the wrinkles?
 Ribbon-adhered EPS insulated roof specimen

17. 17
What parameters impact wrinkling?
Dimensional Movement of Insulation
 Insulation gap measurements from the EPS roof specimens
indicate that:
› Gap widened as insulation temperature lowered, insulation shrinking
› Gap narrowed as the insulation temperature increased—until around
80°C, at which point the gap widened at a significant rate and this
change was permanent

18. 18
What parameters impact wrinkling?
Dimensional Movement of Insulation
 Insulation gap measurements from the SW roof specimens
indicate no noticeable change in gap width
› There was actually a very small amount of movement in the gap in the
opposite direction one would expect, likely due to dimensional
movement of other components of the system

19. 19
What parameters impact wrinkling?
Dimensional Movement of Insulation
 Insulation gap measurements from the Polyiso roof specimens
indicate that:
› Gap widened as insulation temperature lowered, insulation shrinking
› Gap narrowed as the insulation temperature increased until the boards
came in to contact
› Boards remained in contact at high temperature

20. 20
What parameters impact wrinkling?
Dimensional Movement of Insulation (ribbon-adhered)
 Insulation is the only difference in the test specimens

21. 21
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-20 0 20 40 60 80 100
ChangeinGapWidth(mm)
Temperature(°C)
EPS Mech. Fastened
SW Mech. Fastened
Polyiso Mech.
Fastened
What parameters impact wrinkling?

22. 22
What parameters impact wrinkling?
Impact of Cover Board Material
 Mechanically Fastened EPS roof specimen
 Flexible, Loose-laid, Sanded Underlayment (Previously Tested)
No Wrinkles, sagging/bulging
Wrinkled
 Rigid Asphalt Cover Board
 Fibreboard Cover Board

23. 23
Impact of Cover Board Material
 Mechanically Fastened EPS roof
specimens (fibreboard cover
board)
 SBS roof membrane remained
relatively flat compared to
identical roof specimen which
was ribbon-adhered
 Locally reduced thickness of EPS
and consequential bulging of
fastener heads visible through
membrane
What parameters impact wrinkling?

24. 24
Impact of Cover Board & Attachment Strategy
 Ribbon-adhered EPS roof
specimens (asphalt cover board)
 Experienced ridging along the
length of the specimen typically
between the ribbons of the
adhesive
What parameters impact wrinkling?

25. 25
What parameters impact wrinkling?
Impact of Attachment Technique
 Mechanically Fastened vs. Ribbon-Adhered with EPS Insulation

26. 26
Summary
 Able to reproduce wrinkles in the lab that appear similar to
wrinkles observed in the field
 EPS insulation was present in all of the laboratory roof
specimens for which wrinkling occurred
 Rigid cover boards can help reduce wrinkling, but underlying
insulation is still damaged
 Attachment technique does impact the amount of wrinkling
when a cover board is used, with mechanically fastened
systems with rigid cover boards showing the least wrinkling

27. 27
Next Steps
 Exposure of the roof specimens to more realistic conditions
including arrangements with a temperature gradient
 Examination of potential methods to protect temperature
sensitive insulation layers from extreme temperatures
 These are actually already done, but in a separate paper.
See you at RCI!
 Perform field investigations to assess patterns with
regards to components of assembly, climate, etc
 Perform field monitoring of insulation and membrane
movement to assess in-situ performance

28. 28
Next Steps
 This research is live!

29. 29
Next Steps

30. 30

31. 31
Next Steps

32. 32
Next Steps

33. 33
Discussion + Questions
FOR FURTHER INFORMATION PLEASE VISIT
 www.rdh.com
 www.buildingsciencelabs.com
OR CONTACT US AT
 Lorne Ricketts - lricketts@rdh.com