SUSTAINABLE BUILDINGS: ADDRESSING LONG-TERM BUILDING ENVELOPE DURABILITY Dr. James L. Hoff Center...

SUSTAINABLE BUILDINGS: ADDRESSING LONG-TERM BUILDING

ENVELOPE DURABILITY

Dr. James L. Hoff

Center for Environmental Innovation in Roofing / TEGNOS Research, Inc.

Durability & Green Rating Systems

Durability is a necessity to achieve long-term sustainability …

… but many green building rating systems provide little assurance that durability is adequately addressed.

“The majority of green building assessment systems focus on the design of the constructed building, with little focus on the effect of the building system’s life during operation. This tendency has resulted in a failure of many rating systems to properly consider durability, lifecycle cost, and the effects of premature building envelope failures.”


“Green Assessment Tools: The Integration of Building Envelope Durability. “ (McCay, 2008, p. 1)


Too much focus on design, too little focus on operation…

... resulting in a failure to address:

– True life cycle cost

– Risk of premature failures

What is Durability?

What is Durability?

A dictionary definition:

“… the ability to exist for a long time without significant deterioration.”

Merriam-Webster Online Dictionary

What is Durability?

A building standards definition:“… the ability of a building or any of its components to perform its required functions in its service environment over a period of time without unforeseen cost for maintenance or repair.”

Canadian Standards Association “Guideline on Durability in Buildings” (CSA S478-95, Rev. 2001)

What is Durability?

The ability of a building or any of its components to:

– perform its required functions

– in its service environment

– over a period of time

– without unforeseen cost for maintenance or repair

Roof Durability Characteristics

Perform Required Functions

• Resist and re-direct moisture

• Resist air & vapor movement

• Resist thermal transfer

• Resist fire, wind, hail, and other loads

• Serve as a working platform for:

– Rooftop mechanical equipment– Solar / PV installations– Garden roofing installations


In Its Service Environment

• Climatic Environment– High wind / wind-blown debris zones– Severe hail zones– Cold climates / severe freeze-thaw zones– Warm climates / high uv zones

• Operating Environment– Frequency / density of use– Occupant capabilities / attitudes– Frequency / complexity of maintenance


Over a Period of Time

Period of Time =

Intended Service Life

… More to Follow


Without Unforeseen Cost…

Implies Some Level of Cost Should Be Foreseen!

Implies Planning Is Be Necessary!


Without Unforeseen Cost for..

• Maintenance– Frequent & ongoing– Includes inspection, assessment, service, &

minor repairs

• Repair– Infrequent, but generally planned– Includes renovation, retrofitting, component

replacement

Durability & Green Building Design

The Major Issues

• Justifying Vital Service Functions in Green Design Assessment

• Incorporating Reliable Service Life Expectations into Green Design


Vital Service Functions

Example:Installing a High Density Cover Board

over Low Density Roof Insulation

MembraneCover Board

Insulation

Environmental Benefits:+ Reduced Damage+ Longer Service Life+ Lower Life Cycle Impact

Environmental Costs:– Added Materials– Added Energy– Added Waste

Unless the benefits of the cover board are recognized in the overall project assessment, the cover board may be viewed only as adding to environmental costs:



MembraneCover Board

Insulation

Environmental Benefits:+ Reduced Damage+ Longer Service Life+ Lower Life Cycle Impact

Environmental Costs:– Added Materials– Added Energy– Added Waste

Other Examples:

• Thicker roofing membranes

• Redundant flashing details

Will the project assessment recognize the added value of such enhanced service

functions?




Incorporating Vital Service Functions

Performance Standards



• Prove Their Value through Research– Drawing from the past– Adding certainty to the future.

• Identify Their Value with Measurement– Providing measurable and reproducible value– Balancing environmental impact with added

performance.

In order to incorporate vital service functions, performance standards must…



Research examples & options:

• Failure Analysis (e.g. Bailey & Bradford field studies)

• Destructive Testing (e.g. Koontz et al. hail testing)

• Performance Testing (e.g. ORNL thermal testing)


Performance StandardsBenefits Needing Definition:

(Examples)

What is the measurable value (benefit less impact) of:

– Multiple & staggered insulation layers?

– Cover boards?

– Increased membrane thicknesses?

– Redundant flashing details?


Performance Standards and the Roofing Industry

By definition, sustainable buildings must be buildings that perform: so performance standards are more important than ever …

… but without credible roofing industry performance standards, others may establish the standards for us.



A spirit of industry cooperation is emerging that could foster expanded performance standards activities …

… but credible roofing industry standards may require a much higher level of research activity and funding.



• An Up-To-Date & Active Research Agenda– To identify & address the critical “gaps”– To identify resources & funding– To monitor & measure progress

• A Research-Driven Standards Process– A consensus process … – Using research results to validate industry practice

What The Industry Needs:


Service Life Expectations

How do we identify service life today?


Service Life Expectations

How can we identify service life today?

• Anecdotal field reports

• Opinion surveys

• Historical end-of-service studies

• Agency approval reports

• Manufacturer warranty offerings


Service Life Estimates for Low-Slope Roofing Systems(Years)

Opinion Survey1

16.6

16.6

N/A2

14.1

No Data

System Type

Asphalt BUR

SBS Modified

PVC

EPDM

TPO

Historical Study3

13.6

17.3

N/A2

16.8 – 18.4

No Data

Agency Report4

20

20

35

20

20

Warranty Offering5

20

20

15

30

30

Data Source

1Mean service life from Cash (1997), based on an opinion survey of industry participants.2Data from the Cash & Schneider studies involved discontinued formulations of PVC that do not allow the data to be meaningful.3Mean service life from Schneider & Keenan (1997), based on end-of-service field reports.4Estimated service life from British Board of Agrément Technical Approvals (BBA, 2008):5Published warranty offerings from NRCA Low Slope Roofing Materials Guide, 2006-07, Vol. 2, Section 5 Roof Membrane Warranties.


Service Life Estimates

Different Estimates – Different Assumptions:

• Time Assumptions– Backward looking– Forward looking

• Quality Assumptions– Uncontrolled sample: Assuming the worst– Controlled sample: Assuming the best


Service Life Assumptions: Going Forward

• Time Assumptions: Roofs perform in the future, not the past … … but the future is never certain.

• Quality Assumptions: Assuming the best may be overly optimistic …… but assuming the worst understates the value of good design, installation and maintenance.

• Mixed Assumptions: Only increase marketplace confusion.


Incorporating Service Life Expectations

Durability Planning


Durability Planning

• Emphasis on Process– A management system– Similar to ISO 9000 & ISO 14000

• Emphasis on Shared Responsibility– Identifies stakeholders– Identifies roles


Durability Planning and Canadian Standard S478-95

Three Basic Steps:

1. Identify Durability Determinants

2. Identify Durability Interventions

3. Develop Action Plan & Timetable


Durability Planning

1. Identify Durability Determinants:

• Provide the Required Functions

• In the Service Environment

• By Key System Element


Durability Planning

2. Identify Durability Countermeasures:

• During Design

• During Material Selection

• During Application & Commissioning

• During Service Life

• At End of Service


Durability Planning

3. Develop Action Plan & Timetable

• Periodic & Ongoing

• At Specified Times


Durability Planning

A Suggested Durability Planning Matrix

(See Appendix A)

The Service Environment

Required Functions

Ro

of

Sys

tem

E

lem

en

ts


Durability Planning Matrix

The Service Environment

Required Functions

Ro

of

Sys

tem

E

lem

en

ts

Design Criteria

MaterialCriteria

ApplicationCriteria

CommissioningCriteria


Durability Planning Matrix (cont.)

Operating / Maintenance Criteria

Ongoing & Periodic

At XYears

At X+Years

At End of Service


Durability Planning Matrix (cont.)

• Establish and an Up-To-Date and Active Industry Research Agenda

• Increase Research Activity, Emphasizing Key Roofing Components & Details

• Re-Invigorate Consensus Standards Activity with New Research & New Commitment

• Start Incorporating Durability Planning in Roofing Specifications

• Continue to Advocate the Importance of Roof Durability


Recommendations Going Forward

SUSTAINABLE BUILDINGS: ADDRESSING LONG-TERM BUILDING

ENVELOPE DURABILITY

Dr. James L. Hoff

Center for Environmental Innovation in Roofing / TEGNOS Research, Inc.

SUSTAINABLE BUILDINGS: ADDRESSING LONG-TERM BUILDING ENVELOPE DURABILITY Dr. James L. Hoff Center...

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