Detailing The Differential: Tricky Transitions in Commercial Roofing

Detailing the Differential
Tricky Transitions in Commercial Roofing
Jennifer Keegan, AAIA

Director, Building and Roofing Science
Kristin Westover, P.E., LEED AP O+M

Technical Manager, Specialty Installations
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Today’s Learning Objectives
Discuss requirements to manage moisture, air, vapor, and thermal continuity
Evaluate code requirements and how to achieve compliance
Discuss the “whys” behind the details for these tricky transitions
Review the importance of coordination and execution


Construction
Photos of details gone wrong?
steep-slope to low-slope integration, rising walls, clerestories, parapets and drainage
Image courtesy of The Journal of Light Construction

Image courtesy of Birds Eye Roofing Image courtesy of Phil Dregger
Image courtesy of Corey Zussman
Image courtesy of Renderosity

The 4 Main Control Layers
WATER Roof Membrane

AIR
Rigid Insulation
Air/Vapor Barrier
Substrate
Board
THERMAL Roof Membrane

VAPOR
Rigid Insulation
Air/Vapor Barrier
Substrate
Board
12
Considerations
• Continuity of control layers
• Pressures from wind, stack effect
• Condensation potential/risk
• Differential movement
13
What is the difference between the control layers?
Diffusion (moisture vapor) Air Transport (moisture vapor) Bulk Water

1x 10x to 100x >1000x
Vapor Retarder Air Barrier Membrane
Air Control – Air Transportation
Types of Air
Movement
INTRUSION
AIR LEAKAGE = EXFILTRATION & INFILTRATION

Air Control – Energy Impact
Air infiltration and exfiltration make-up are
25%–40% of total heat loss in a cold climate
ROOF
16
BUILDING ENVELOPE
Graphic courtesy of Energy Shield
Images courtesy of SmithGroup “The Hidden Science of High-Performance Building Assemblies,” Environmental Building News, November 2012
Control Layer – Enclosure Continuity
Four Control Layers:
Water, Air, Thermal, and Vapor
Continuity of control layers across all six sides

of the Building Enclosure using the pen test
Building Enclosure (ASTM E2947):

“… materials, components, systems, and
assemblies intended to provide shelter and
environmental separation between interior
and exterior, or between two or more
environmentally distinct interior spaces in a
building or structure.”
17

Codes & Specs Overview
Building Code
• Prescriptive Requirements
• Reference Standards
Energy Code
• Prescriptive Requirements
19
• Performance Modeling
Building Code - Prescriptive Requirements
Chapter 14: Exterior Walls
“exterior walls, wall coverings, & components”
2018
INTERNATIONAL
• Weather Protection (1402.2)
BUILDING CODE • Vapor Retarders (1404.3)
• Flashing (1404.4)
“Flashing shall be installed … to prevent

moisture from entering the wall or to
redirect that moisture to the exterior.”
Building Code - Prescriptive Requirements
Chapter 15: Roof Assemblies & Rooftop Structures
“…design, materials, construction and quality of roof
2018
assemblies, and rooftop structures”
• Weather Protection (1503)
INTERNATIONAL • Requirements for Roof Coverings (1507)
BUILDING CODE
• Flashing (1503.2)
• Coping (1503.3)
• Wind Resistance of Roofs (1504.1 ->ASCE 7)
• Edge Securement, Low-slope Roofs (1504.5)
designed & installed per the IBC & the
manufacturer's approved instructions.
Reference Standards - Performance Requirements
ASCE 7 – Design Wind Pressures
• Roof deck and coverings shall be designed in
accordance with ASCE 7 (IBC 1609.5)
Energy Code – Commercial Requirements
Energy Efficiency (IBC Chapter 13 )

Buildings shall be designed and constructed in
2018 accordance with the International Energy Conservation
Code - 1301.1.1
INTERNATIONAL Comply with one of the following:

ENERGY CONSERVATION
CODE • Requirements of ANSI/ASHRAE/IESNA 90.1
• Requirements of IECC
IECC Commercial Provisions “…apply to all buildings

except for residential buildings 3 stories or less in height”
Energy Code – Thermal Requirements
Insulation - Climate Zones (IECC C301.1 and 90.1 Annex 1)
• Building thermal
envelope depiction
(Section C103.2)
• Climate Zone dictates

minimum R-Value
Energy Code – Air Leakage Requirements
Air Barrier - (IECC C402.5 & 90.1 5.4.3.1)
“Combination of interconnected materials, assemblies, and sealed
joints and components… minimizing air leakage into or out of the
building envelope.”
Air Barrier Design (IECC C103.2 & 90.1 5.4.3.1.1)

• Components, Joints & Penetrations detailed
• Extending over all surfaces, including the roof
• Resist pressures from wind, mechanical, stack effect
Air Barrier Installation (IECC C402.5.1.1 & 90.1 5.4.3.1.2)

• Junctions between walls and roofs or ceilings
• Penetrations at roofs, walls, and floors
• Joints, seams, & connections between planes
Image adapted from: Illustrated Guide - Achieving Airtight Buildings, BC Housing


Roofing basics
Roofing basics - Low-slope
Keys for success:

• Correct flashing
heights
• Slope to drain
• Sealing the control
layers
Roofing basics- Low-slope



Roofing basics - Steep-slope
Keys for success:

• Correct flashing
heights
• Slope to drain
• Isolation between
incompatible
materials
• Ventilation
Roofing basics - Steep-slope
Roofing basics- Steep-slope
Roofing basics- Steep-slope
Tricky Transitions - Steep-Slope to Low-Slope
Devil is in the Details...
images courtesy of Intertek

Tricky Transitions
Tricky Transitions - Part 2

May end up with this..
Image courtesy of Intertek

Pre-construction Meeting
• Initiates communication
among construction team
members
• Resolve potential problems
prior to start
• Review schedule and
sequencing of activities
Pre-construction Meeting
• Job Site Conditions
• Storage and Protection of
Materials
• Protection of Completed
Work
• Weather
• Damage resulting from
subsequent construction
Construction
• Regular progress
meetings
• Coordination with
other trades
• On-site visits
After Construction
• Liability
• Reputation
• Subsequent jobs
Summary
• 4 Control Layers - must be

continuous and tied together
• Code requirements - dictate
performance and
prescriptive requirements
• Tricky Transitions -
remember the roofing basics
• Coordination & Execution - a
successful construction
project starts during pre-
construction
Building & Roofing Science Team
Tom Taylor, PhD

Kristin Westover, PE
James R. Kirby, AIA
Benjamin Meyer, AIA
BuildingScience@GAF.com
Thank you for your time!
This concludes The American Institute of Architects Continuing

Education Systems Course
Questions?
Continuing Education:
ceu@bnpmedia.com
Webinars:
webinars@bnpmedia.com
Detailing the Differential
Tricky Transitions in Commercial Roofing

Director, Building and Roofing Science
jennifer.keegan@gaf.com
Kristin Westover, P.E., LEED AP O+M

Technical Manager, Specialty Installations
kristin.westover@gaf.com

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Detailing the Differential

Tricky Transitions in Commercial Roofing

Jennifer Keegan, AAIA

Kristin Westover, P.E., LEED AP O+M

To receive a Certificate of Completion, you must complete and pass

This course is registered with AIA CES for continuing professional

Evaluate code requirements and how to achieve compliance

Review the importance of coordination and execution

Evaluate code requirements and how to achieve compliance

Review the importance of coordination and execution

Image courtesy of The Journal of Light Construction

Image courtesy of Renderosity

WATER Roof Membrane

THERMAL Roof Membrane

Diffusion (moisture vapor) Air Transport (moisture vapor) Bulk Water

AIR LEAKAGE = EXFILTRATION & INFILTRATION

Graphic courtesy of Energy Shield

Continuity of control layers across all six sides

Building Enclosure (ASTM E2947):

Evaluate code requirements and how to achieve compliance

Review the importance of coordination and execution

“Flashing shall be installed … to prevent

Energy Efficiency (IBC Chapter 13 )

INTERNATIONAL Comply with one of the following:

IECC Commercial Provisions “…apply to all buildings

• Climate Zone dictates

Air Barrier Design (IECC C103.2 & 90.1 5.4.3.1.1)

Air Barrier Installation (IECC C402.5.1.1 & 90.1 5.4.3.1.2)

Image adapted from: Illustrated Guide - Achieving Airtight Buildings, BC Housing

Evaluate code requirements and how to achieve compliance

Review the importance of coordination and execution

Keys for success:

Image courtesy of The Journal of Light Construction

Image courtesy of The Journal of Light Construction

Image courtesy of The Journal of Light Construction

Keys for success:

images courtesy of Intertek

Evaluate code requirements and how to achieve compliance

Review the importance of coordination and execution

Image courtesy of Intertek

• 4 Control Layers - must be

Tom Taylor, PhD

This concludes The American Institute of Architects Continuing

Jennifer Keegan, AAIA

Kristin Westover, P.E., LEED AP O+M

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