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C R O S S - L A M I N A

T E D T I M B E R

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© 2013 FPInnovations and Binational Softwood Lumber Council. All rights reserved.

The U.S. Edition of the CLT Handbook: cross-laminated timber can be electronically downloaded without charge from the websitewww.masstimber.com. Additional information can be obtained by visiting the websites of FPInnovations, USFPL, American Wood Council

(AWC), APA and U.S. WoodWorks. Hard copies can be obtained through AWC (www.awc.org).

No part of this published Work may be reproduced, published, or transmitted for commercial purposes, in any form or by any means,

electronic, mechanical, photocopying, recording or otherwise, w hether or not in translated form, without the prior written permission ofFPInnovations and Binational Softwood Lumber Council.

The information contained in this Work represents current research results and technical information made available from many sources,

including researchers, manufacturers, and design professionals. The information has been reviewed by professionals in wood designincluding professors, design engineers and architects, and wood product manufacturers. While every reasonable effort has been made toinsure the accuracy of the information presented, and special effort has been made to assure that the information reflects the state-of-

the-art, none of the above-mentioned parties make any warranty, expressed or implied, or assume any legal liability or responsibilityfor the use, application of, and/or reference to opinions, findings, conclusions, or recommendations included in this published work, norassume any responsibility for the accuracy or completeness of the information or its fitness for any particular purpose.

This published Work is designed to provide accurate, authoritative information but is not intended to provide professional advice.It is the responsibility of users to exercise professional knowledge and judgment in the use of the information.


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Edited by

Erol Karacabeyli, P.Eng., FPInnovationsBrad Douglas, P.E., AWC

FPInnovations

Pointe-Claire, QC

Special Publication SP-529E

2013

C L

C

R O S S - L A M I N A T E D T I M B E R


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Funding for this publicationwas provided by

Publication

FPInnovations

Distribution of hard copies

AWC

570 boul. St. JeanPointe-Claire (QC)H9R 3J9www.fpinnovations.ca

222 Catoctin Circle SESuite 201Leesburg, VA 20175www.awc.org

Library and Archives Canada Cataloguing in Publication

CL handbook : cross-laminated timber / edited by Erol Karacabeyli,Brad Douglas. -- U.S. ed.

(Special publication, ISSN 1925-0495 ; SP-529E)Co-published by U.S. Department o Agriculture, Forest Service, Forest

Products Laboratory, Binational Sofwood Lumber Council (BSLC).Includes bibliographical reerences.Issued also in electronic ormat.

ISBN 978-0-86488-553-1 1. Laminated wood. 2. Laminated wood construction. 3. Engineered

wood construction. 4. Laminated wood--Standards. 5. Laminated wood--Handbooks, manuals, etc. I. Karacabeyli, Erol, 1954- II. Douglas, Brad, 1960-III. Forest Products Laboratory (U.S.) IV. FPInnovations (Institute)

V. Binational Sofwood Lumber Council VI. itle: Cross-laminated timber. VII. Series: Special publication (FPInnovations (Institute)) ; SP-529E

A666.C57 2013 624.1’84 C2012-908154-X

Library and Archives Canada Cataloguing in Publication

CL handbook [electronic resource] : cross-laminated timber / editedby Erol Karacabeyli, Brad Douglas. -- U.S. ed.

(Special publication, ISSN 1925-0509 ; SP-529E)Co-published by U.S. Department o Agriculture, Forest Service, Forest

Products Laboratory, Binational Sofwood Lumber Council (BSLC).Includes bibliographical reerences.Electronic monograph in PDF ormat.Issued also in print ormat.ISBN 978-0-86488-554-8

1. Laminated wood. 2. Laminated wood construction. 3. Engineered wood construction. 4. Laminated wood--Standards. 5. Laminated wood--

Handbooks, manuals, etc. I. Karacabeyli, Erol, 1954- II. Douglas, Brad, 1960-III. Forest Products Laboratory (U.S.) IV. FPInnovations (Institute)

V. Binational Sofwood Lumber Council VI. itle: Cross-laminated timber. VII. Series: Special publication (FPInnovations (Institute) : Online) ; SP-529E

A666.C57 2013 624.1’84 C2012-908155-8

AMERICAN

WOOD

COUNCIL


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PREFACEExpansion into mid-rise, high-rise and non-residential applications presents one o the most promising avenuesor the North American wood industry to diversiy its end use markets. Tis may be achieved by:

■

Designing to new building heights with Light Frame Wood Construction ■ Revival o Heavy Timber Frame Construction

■ Adoption o Cross-laminated Timber (CL)

■ Facilitating Hybrid Construction

Tere are concerted efforts both in Canada and in the United States towards realizing that goal. In act, theCanadian provinces o British Columbia and uebec went even urther and created specific initiatives to supportthe use o wood in those applications.

Tis Handbook is ocused on one o these options – adoption o cross-laminated timber (CL). CL is aninnovative wood product that was introduced in the early 1990s in Austria and Germany and has been gaining

popularity in residential and non-residential applications in Europe. Te Research and Standards Subcommitteeo the industry’s CL Steering Committee identified CL as a great addition to the “ wood product toolbox ” and

expects CL to enhance the re-introduction o wood-based systems in applications such as 5- to 10-story buildings where heavy timber systems were used a century ago. Several manuacturers have started to produce CL in NorthAmerica, and their products have already been used in the construction o a number o buildings.

CL, like other structural wood-based products, lends itsel well to preabrication, resulting in very rapidconstruction, and dismantling at the end o its service lie. Te added benefit o being made rom a renewableresource makes all wood-based systems desirable rom a sustainability point o view.

In Canada, in order to acilitate the adoption o CL, FPInnovations published the Canadian edition o the CLHandbook in 2011 under the ransormative echnologies Program o Natural Resources Canada. Te broadacceptance o the Canadian CL Handbook in Canada encouraged this project, to develop a U.S. Edition o theCL Handbook. Funding or this project was received rom the Binational Sofwood Lumber Council, ForestryInnovation Investment in British Columbia, and three CL manuacturers, and was spearheaded by a WorkingGroup rom FPInnovations, the American Wood Council (AWC), the U.S. Forest Products Laboratory, APA-TeEngineered Wood Association and U.S. WoodWorks. Te U.S. CL Handbook was developed by a team o over

40 experts rom all over the world.Both CL handbooks serve two objectives:

■ Provide immediate support or the design and construction o CL systems under the alternative or innovativesolutions path in design standards and building codes;

■ Provide technical inormation that can be used or implementation o CL systems as acceptable solutions inbuilding codes and design standards to achieve broader acceptance.

Te implementation o CL in North America marks a new opportunity or cross-border cooperation, as fiveorganizations worked together with the design and construction community, industry, universities, and regulatoryofficials in the development o this Handbook. Tis multi-disciplinary, peer-reviewed CL Handbook is designedto acilitate the adoption o an innovative wood product to enhance the selection o wood-based solutions in non-residential and multi-storey construction.

Credible design teams in different parts o the world are advocating or larger and taller wood structures, as high as30 stories. When asked, they identified the technical inormation compiled in this Handbook as what was neededor those applications.

A Renaissance in wood construction is underway; stay connected.


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ACKNOWLEDGEMENTSTe great challenge with this U.S. Edition o the CL Handbook was to gather experts rom theUnited States, Canada and Europe to bring together their expertise and knowledge into a state-o-the-artreerence document. Te realization o this Handbook was made possible with the contribution o many

people and numerous national and international organizations.

Such a piece o work would not be possible without the support rom financing partners and, as such, we would like to express our special thanks to Binational Sofwood Lumber Council, ForestryInnovation Investment (FII), Nordic Engineered Wood, Structurlam, and CL Canada or theirfinancial contribution to this project.

First and most o all, we would like to express our gratitude to AWC, APA, USFPL, FPInnovations,U.S. WoodWorks and their staff or providing the effort and expertise needed to prepare this work. We

would also like to express our special thanks to all chapter authors, co-authors, and reviewers who sharedtheir precious time and expertise in improving this manual.

Our very special thanks go to Loren Ross at AWC and Sylvain Gagnon at FPInnovations or their work as project leaders and or their special efforts in gathering the expertise o everyone into a uniquedocument. Special thanks also go to the Working Group, Dr. Borjen Yeh rom APA, Dave Kretschmann

rom the U.S. Forest Products Laboratory, and Lisa Podesto rom U.S. WoodWorks. Tanks also toMadeline Leroux or her work on the drawings, Odile Fleury or her help with bibliographic reerences,and Marie-Claude Tibault or her support in editing and coordination work.

Erol Karacabeyli, P.Eng. and Brad Douglas, P.E.Co-editorsCLT Handbook, U.S. Edition


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CONTENTS Introduction

to cross-laminated timber Cross-laminated

timber manuacturing

Structural design ocross-laminated timber elements

Lateral design o

cross-laminated timber buildings

Connections incross-laminated timber buildings

Duration o load and creep actorsor cross-laminated timber panels

Vibration perormance ocross-laminated timber floors

Fire perormance ocross-laminated timber assemblies

Sound insulation ocross-laminated timber assemblies

Building enclosure design orcross-laminated timber construction

Environmental perormanceo cross-laminated timber

Lifing and handling ocross-laminated timber elements

C H A P T E R

12


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E

n v i r o n m e n t a l p e r f o r m a n c e

f l i d i b

11C H A P T E R Authors

Jennifer O’Connor, M.Arch., FPInnovationsLisa Podesto, M.S., P.E., WoodWorks

Alpha Barry, Ph.D., MBA, FPInnovationsBlane Grann, M.Sc., FPInnovations

Peer Reviewers

Kenneth Bland, P.E., American Wood CouncilLiv Haselbach, Ph.D., P.E., LEED-AP BD+C, Washington State University


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Te U.S. Edition o the CL Handbook: cross-laminated timber combines the work and knowledge o American,Canadian and European specialists. Te handbook is based on the original Canadian Edition o the CLHandbook: cross-laminated timber , that was developed using a series o reports initially prepared by FPInnovations

and collaborators to support the introduction o CL in the North American market. A multi-disciplinary teamrevised, updated and implemented their know-how and technologies to adapt this document to U.S. standards.

Te publication o this handbook was made possible with the special collaboration o the ollowing partners:

Te editing partners would also like to express their special thanks to Binational Sofwood Lumber Council,Forestry Innovation Investment (FII), Nordic Engineered Wood, Structurlam, and CL Canada or theirfinancial contribution to studies in support o the introduction o cross-laminated timber products in theUnited States o America.

ACKNOWLEDGEMENTS

AMERICAN

WOOD

COUNCIL

© 2013 FPInnovations and Binational Softwood Lumber Council. All rights reserved.

The U.S. Edition of the CLT Handbook: cross-laminated timber can be electronically downloaded without charge from the website www.masstimber.com.Additional information can be obtained by visiting the websites of FPInnovations, USFPL, American Wood Council (AWC), APA and U.S. WoodWorks.Hard copies can be obtained through AWC (www.awc.org).

No part of this published Work may be reproduced, published, or transmitted for commercial purposes, in any form or by any means, electronic,mechanical, photocopying, recording or otherwise, whether or not in translated form, without the prior written permission of FPInnovations andBinational Softwood Lumber Council.

The information contained in this Work represents current research results and technical information made available from many sources, includingresearchers, manufacturers, and design professionals. The information has been reviewed by professionals in wood design including professors, designengineers and architects, and wood product manufacturers. While every reasonable effort has been made to insure the accuracy of the informationpresented, and special effort has been made to assure that the information reflects the state-of-the-art, none of the above-mentioned parties makeany warranty, expressed or implied, or assume any legal liability or responsibility for the use, application of, and/or reference to opinions, findings,conclusions, or recommendations included in this published work, nor assume any responsibility for the accuracy or completeness of the informationor its fitness for any particular purpose.

This published Work is designed to provide accurate, authoritative information but is not intended to provide professional advice. It is the responsibilityof users to exercise professional knowledge and judgment in the use of the information.


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CHAPTER 11 Environmentaliii

ABSTRACT

Te environmental ootprint o CL is requently discussed as potentially beneficial when compared tounctionally equivalent non-wood alternatives, particularly concrete systems.

In this Chapter, the role o CL in sustainable design is addressed. Te embodied environmental impacts oCL in a mid-rise building are discussed, with preliminary results rom a comprehensive lie cycle assessment(LCA) study.

We also discuss other aspects o CL’s environmental profile, including impact on the orest resource and impacton indoor air quality rom CL emissions. Te ability o the North American orest to sustainably support aCL industry is an important consideration and is assessed rom several angles, including a companion discussionregarding efficient use o material. Market projections and orest growth-removal ratios are applied to reacha clear conclusion that CL will not create a challenge to the sustainable orest practices currently in place inNorth America and saeguarded through legislation and/or third party certification programs.

o assess potential impact on indoor air quality, CL products with different thicknesses and glue lines weretested or their volatile organic compounds (VOCs) including ormaldehyde and acetaldehyde emissions. CL

was ound to be in compliance with European labeling programs as well as the most stringent CARB limits orormaldehyde emissions. esting was done on Canadian species, as there was no U.S. supplier o CL at the timeo this writing; because VOC emissions are affected by species, this work should be repeated or products maderom different species.


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CHAPTER 11 Environmentaliv

TABLE OF CONTENTS

Acknowledgements ii

Abstract iii

1 Introduction 12 Lie Cycle Environmental Impacts o a CL Mid-rise Building 2

2.1 Description o the LCA Study 2

2.2 Results 3

3 Potential Indoor Air uality Impacts o Using CL in Buildings 8

4 Resource Assessment: Impact o CL on the Forest 9

5 Potential Contribution o CL to Green Building Objectives 13

6 Material Disclosure 16

7 Conclusions 17

8

Reerences 18Appendix A: Literature Review 22

A1 Literature Review on Environmental Perormance o CL 22

Appendix B: Details on the Mid-rise LCA Study 24

B1 Objective and Method 24

B1.1 Lie Cycle Inventory 26

B2 Results 29

B2.1 Assumptions and Limitations 30

B2.2 Sensitivity 31

B3 Discussion 32

B3.1 End-o-lie Scenarios 32

B3.2 Carbon Storage 32

Appendix C: Details o the VOC esting 34

C1 Objectives and Background 34


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CHAPTER 11 Environmentalv

C2 Procedures and Results 34

C2.1 Materials Sampling, Packaging, ransportation and Conditioning 34

C2.2 Method 35

C2.3 uantification o Formaldehyde 38C2.4 uantification o the VOC 38

C3 Results and Discussions 38

C4 Conclusions and Recommendations 45


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CHAPTER 11 Environmentalvi

List o ablesTable 1 Material disposal assumptions 28

Table 2 Absolute values or total lie cycle impacts 29

Table 3 Small chamber operating conditions 36

Table 4 DU/GC/MS and HPLC operating conditions 37

Table 5 Samples 24-hour individual VOCs (iVOCs), VOC as toluene, between n-C6and n-C16 including ormaldehyde (µg/m) 39

Table 6 Samples 24-hour individual VOCs (iVOCs), VOC as toluene, between n-C6and n-C16 including ormaldehyde (µg/m) 40

Table 7 Example o some European emission labeling systems 42

Table 8 Samples 24-hour iVOCs, VOC as toluene, between n-C6 and n-C16 emissionactors including ormaldehyde (µg/m.h) 43

Table 9 Samples 24-hour iVOCs, VOC as toluene, between n-C6 and n-C16 emissionactors including ormaldehyde (µg/m.h) 44

Table 10 24-hour ormaldehyde emissions as a unction o product types 45

List o Figures Figure 1 Preliminary LCA results relative lie cycle impacts, excluding operational phase

and equivalent building components, broken down by lie cycle stage 4

Figure 2 Results normalized to total U.S. results rom 1999 using data rom Bare, Gloria & Norris (2006) 6

Figure 3 Growth-removal ratios by sofwoods and hardwoods, 1952-2006 11

Figure 4 Certified orest area in North America as o August 2012 12

Figure 5 System boundary 25

Figure 6 Picture showing a prepared sample with edges sealed ready to be put in the chamber 35

Figure 7 A general view o the 1 m environmental chamber used or emissions testing 36

Figure 8 24-hour VOCs including ormaldehyde and acetaldehyde off gassing as a unction o samples types 40

Figure 9 24-hour VOCs including ormaldehyde and acetaldehyde off gassing as a unction o samples types 41

Figure 10 24-hour VOC emissions as a unction o cross-laminated products 41


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CHAPTER 11 Environmental1

1INTRODUCTION

Te environmental ootprint o CL is requently discussed as beneficial. Tis Chapter considers the criteriaor determining environmental perormance o CL systems; we also quantiy that perormance where possible.

Environmental expectations or CL would align with common sustainable design objectives. For example,some questions that might be asked o CL include:

• What are the embodied lie cycle assessment impacts o CL buildings?

• Does CL adversely affect indoor air quality?

• Does it minimize the use o materials?

• Does it reduce operating energy in buildings?

• Does it contain recycled material?• Is there enough orest to sustainably support manuacturing?

Tis is not an exhaustive list o sustainability criteria but a good starting point. In this Chapter, we addressin detail the questions o embodied effects, indoor air quality and orest resource. Specific embodied effectsexamined include consumption o material and energy resources, creation o solid wastes, and lie cycle assessmentimpact measures such as global warming potential, acidification potential and eutrophication potential. We touchon other topics throughout the Chapter and in our closing remarks.

As we will show in this Chapter, the attributes o CL construction systems are consistent with some importantsustainable design criteria.


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2LIFE CYCLE

ENVIRONMENTALIMPACTS OF A CLTMID-RISE BUILDING

One o the most valuable tools or measuring environmental impacts o a product or process is lie cycle assessment(LCA). LCA is a scientific technique, guided by international standards, to measure flows between a productand nature and to assess the impact o those flows in categories such as global warming potential, acidification

potential and smog potential.

Manuacturers use LCA to identiy environmental hot spots in the lie cycle o their products so thatimprovements can be sought. In addition, i LCA data exists or most construction products, designers can

perorm an LCA or whole buildings and compare impacts o different material decisions. Publically-availableLCA data also helps meet a potential market demand or environmental disclosure rom manuacturers inspired,or example, by the LEED® program.

An LCA or North American CL has been published (Athena Sustainable Materials Institute, 2012b).Tis product inormation allows us to calculate various embodied impacts o a CL building. In this section,

we provide preliminary findings or a LCA study o a mid-rise CL building, which are to be published in acomparative building LCA by FPInnovations in 2013. Te intended use o the results in a comparative LCA leadsto the exclusion o several building components rom the analysis which were deemed to be identical between theCL building and the building it will be compared with. Building components excluded rom this study include:oundation walls, windows, doors, plumbing, electrical, hand railings, and HVAC equipment. Please seeAppendix B or ull details o the assessment method or these preliminary results.

2.1 Description o the LCA Study Te LCA study was perormed on an existing CL apartment building located in uébec, Canada. Te building is

43,700 square eet in area (4,060 square meters) and has our stories plus one underground level. A brie overviewo the study along with results and discussion are provided below. Reer to Appendix B or additional inormationon the methodolog y, assumptions, limitations, parameter sensitivity and additional discussion.

Te Athena Impact Estimator or Buildings is an LCA-based modeling tool that was used in this analysis, along with additional methods to address gaps in the Impact Estimator. Te Impact Estimator provides cradle-to-graveLCA results; in other words, it includes the impacts o resource extraction and material production, construction,


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maintenance and replacement, demolition, and associated transport processes. In this study, the building lietimeis assumed to be 60 years. Operating energy is not included in the assessment, in order to better isolate theembodied impacts o the materials.

Te Impact Estimator draws on embedded LCA databases or materials, construction processes, maintenanceand replacement activities, transportation and energy. Because CL systems are not yet included in the ImpactEstimator, additional LCA resources had to be applied to this analysis. Specifically, this study augmented ImpactEstimator results using data rom a published LCA study or the CL product that was used in this building(Athena Sustainable Materials Institute, 2012b).

Te Impact Estimator produces a subset o results according to a common North American impact assessmentmethod known as RACI1. Tese impact categories rom RACI include:

• Global Warming Potential (GWP measured in kg o CO2 equivalent)

• Acidification Potential (AP measured in moles o hydrogen ion (H+) equivalents)

• Respiratory Effects (RE measured in kg o particulate matter (PM) up to 10 microns)

• Eutrophication Potential (EP measured in kg nitrogen (N) equivalent)• Ozone Depletion Potential (OD measured in kg chlorofluorocarbon-11 (CFC-11) equivalent)

• Smog Potential (measured in kg o ozone (O3) equivalent)

Te Impact Estimator excludes RACI impacts or human toxicity and ecotoxicity, which are listed as optionalmeasures in ISO 21930 (2007) due to greater uncertainty in these measures. Fossil uel consumption is also anindicator category used by the Impact Estimator which reers to non-renewable ossil uel energy consumption

plus eedstock ossil uel2 and includes direct and indirect energy use along the supply chain.

2.2 ResultsLCA results are best used to help g uide decisions with an understanding that there is always uncertainty in anestimate o uture states. For example, end-o-lie assumptions can make a difference in the results or wood. woend-o-lie scenarios are included or both buildings to consider; landfilling and incineration. An additionalscenario was considered or a second generation CL building where 50% o the CL panels are assumed to berom reused sources and 50% o the CL panels are kept out o the landfill at the end-o-lie or uture reuse.

LCA results or the CL building are given in Figure 1 normalized to the total emissions rom the scenario wherelandfilling is used to dispose o un-recycled materials and no CL panels are reused. In the ollowing paragraphs,the results or each impact category are discussed. Following this, the results are presented normalized to total percapita U.S. emissions in 1999 to help contextualize the magnitude o the results.

In Figure 1, benefits rom substituting the energy content o orest products or ossil uel in the incinerationscenario are kept separate rom total impacts to differentiate between actual emissions and avoided emissions

which, by definition, never physically exist. Te net GWP benefit rom wood products is also presented separately while detailed contributions rom end-o-lie and orest regrowth are discussed in the GWP section.

1 U.S. EPA’s ool or the Reduction and Assessment o Chemical and Other Environmental Impacts (RACI) 2.0 (Bare, 2011).2 Feedstock energy reers to the energy content o the material.


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-300%

-250%

-200%

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-100%

-50%

0%

50%

100%

150%

200%

CLT,LF

CLT,LF,

50%Reuse

CLT,INC

CLT,LF

CLT,LF,

50%Reuse

CLT,INC

CLT,LF

CLT,LF,

50%Reuse

CLT,INC

CLT,LF

CLT,LF,

50%Reuse

CLT,INC

CLT,LF

CLT,LF,

50%Reuse

CLT,INC

CLT,LF

CLT,LF,

50%Reuse

CLT,INC

CLT,LF

CLT,LF,

50%Reuse

CLT,INC

Fossil FuelConsumption

(MJ)

Ozone DepletionPotential

(kg CFC-11 eq)

Additional Forest Sequestration due to CLT Reuse

Fossil Fuel SubstitutionNet GWP from Biogenic SourcesEOLMaintenanceConstructionManufacturing

Global WarmingPotential

(kg CO eq)

AcidificationPotential

(moles of H+ eq)

Respiratory Effects(kg PM10 eq)

EutrophicationPotential(kg N eq)

Smog Potential(kg O eq)

2

R e s u l t s R e l a t i v e t o

C L T ,

L a n d f i l l i n

g

S c e n a r i o

3

Note: wo end-o-lie scenarios were modeled: landfilling (LF) and incineration (INC). In addition, a scenario is shown where 50% reclaimedCL panels are used or the building and 50% o the panels are sent or reuse when the building is demolished. Results are presented relativeto the landfilling scenario with no reused panels. Given that these results are intended to be used in a comparative building LCA published byFPInnovations in 2013, the system boundary excludes operational energy consumption, enestration, oundation elements and other elementsidentified in Appendix B, as these elements were deemed equivalent between the building intended or comparison.

Figure 1Preliminary LCA results relative lie cycle impacts, excluding operational phase and equivalent buildingcomponents, broken down by lie cycle stage

Fossil Fuel Consumption Fossil uel consumption is dominated by the material manuacturing stage. For the scenarios without reused

panels, less than 8% o the emissions rom the material manuacturing stage are due to transportation. Floorsrepresent roughly 50% o ossil uel consumption rom the manuacturing stage which is almost exclusively romCL production. When looking at CL production, roughly 45% o ossil uel use comes rom the manuacturingo CL while another 50% is rom the rough dry lumber. When landfilling is used to dispose o un-recycledmaterials at the end-o-lie, the same building made with 50% reused CL panels allows or a 2% reduction in

ossil uel consumption. Relative to the modeled system, we also see that using wood products to produce heatat the end-o-lie allows or the displacement o a significant quantity o ossil uel use.

Global Warming As the emissions driving GWP largely result rom ossil uel consumption, it is not surprising to find similarcomparative results or GWP and ossil uel consumption. We see significant potential or avoiding emissions inthe incineration scenario when wood is used to produce energy at the end-o-lie and substitute or natural gas use.

For the two scenarios not using reused CL panels, the avoided GWP (-583 metric tons CO2 eq) as carbon is

re-sequestered during orest re-growth on the harvested land more than offsets the GWP rom landfilling withno reused panels (452 metric tons CO

2 eq) and the incineration scenario (472 metric tons CO

2 eq). For the

landfilling scenario with 50% reused panels, the avoided GWP rom orest re-growth is -399 kg CO2 eq while

the landfilling emissions are 249 tons o CO2 eq. Te avoided emissions include the carbon that is re-sequestered

on the land that was harvested to provide the wood or the building, but also the additional carbon that can besequestered rom the continued growth o trees that were not harvested due to the use o reused CL panels ithese trees were to continue to mature. Alternatively, this wood could be harvested and used in another building.At the same time, landfilling emissions are decreased in the scenario with reused CL panels because it is assumedthat 50% o the CL panels are again reused at the end-o-lie with less wood ending up in the landfill.

While methane is released when wood is landfilled, a large portion of wood is permanently sequestered so thatthe net GWP due to biogenic sources for landfilling and incineration is similar over a 100 year period. Appendix B

provides additional information regarding end-of-life modeling.


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Acidification Emissions resulting in acidification were highest for the incineration scenario due to additional stack emissions.However, we also see a significant potential for avoiding acidification when the heat from wood incineration isused to displace natural gas use in a boiler. Te potential for significant reductions in acidification are also foundin a building with 50% reused CL panels due to the high share of total acidification emissions which are dueto CL, the primary building material.

Respiratory Effects Respiratory effects are similar across scenarios as the driver for these emissions are spread across the materialmanufacturing stage of several materials including gypsum, rebar, and concrete, and to a lesser extent mineral

wool and CL. While the combustion of wood products to produce heat at the end-of-life contributes additional particulate emissions, a large portion of these are offset by the direct and indirect emissions from avoided naturalgas use.

Eutrophication Eutrophication emissions result almost exclusively from the landfilling of wood products. Given that landfillingemissions and impacts are very site specific, results from eutrophication should be interpreted with caution. Telandfill modeling undertaken in Simapro v7.3.3 using ecoinvent v2.2 data allows for the exclusion of long-term

(> 100 year) emissions which results in a reduction in eutrophication emissions by a factor of over 100. Teuncertainty involved in modeling the fate and impacts of long-term emissions suggests the need for further caution when interpreting these results. It is possible that the low levels of the emissions driving eutrophication over a long period of time will have minor negative impacts.

Ozone Depletion Ozone depleting emissions also result mainly from landfilling. However, since ozone depleting emissions areshown below to be trivial when normalized to per capita yearly emissions in the United States, they are notdiscussed further.

Smog Significant smog emissions occur across life cycle stages. At the end-of-life, smog emissions are mainly from theincineration of wood, but also from grinding up concrete and chipping wood. During the construction stage,smog emissions are almost exclusively from the transport of materials to the construction site of which the

310 miles (500 km) CL transport is dominant. During the manufacturing stage, smog emissions result fromCL production, the production of concrete and rebar for the footings, as well as from gypsum and mineral

wool production.

Normalization to Per Capita U.S. Emissions in 1999 Normalizing the environmental indicators of an LCA to total yearly per capita levels is useful for determiningthe significance of different impact categories. In Figure 2, results from this study are normalized to per capitaU.S. emissions in 1999 using data from Bare, Gloria & Norris (2006) and the World Bank (2012). Noticeablylong-term eutrophication emissions are quite high. Issues with this indicator have been addressed above. Whileozone depleting emissions are relatively minor, other impact categories are equivalent to between 5 and 15 yearly

per capita U.S. levels in 1999. Relative to the 20 odd apartment suites in the building, these normalized figuresare small. However, the clean hydroelectricity sources in uébec that underpin the production of locally producedmanufactured goods heavily influenced the results from this study. Normalizing GWP emissions (positiveemissions in the graph) for the CL building with landfilling to per capita GHG emissions in uébec in 2009,for example, is equivalent to 27 compared to around 10 in Figure 2 3.

3 Per capita greenhouse gas emissions in the Province o uébec were 10.4 metric tons CO2 equivalent in 2009

(ministère des Finances du uébec, 2012).


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-50

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CLT,LF

CLT,LF,

50%Reuse

CLT,INC

CLT,LF

CLT,LF,

50%Reuse

CLT,INC

CLT,LF

CLT,LF,

50%Reuse

CLT,INC

CLT,LF

CLT,LF,

50%Reuse

CLT,INC

CLT,LF

CLT,LF,

50%Reuse

CLT,INC

CLT,LF

CLT,LF,

50%Reuse

CLT,INC

CLT,LF

CLT,LF,

50%Reuse

CLT,INC

Fossil FuelConsumption*

(MJ)

Ozone DepletionPotential

(kg CFC-11 eq)

Global WarmingPotential

(kg CO eq)

AcidificationPotential

(moles of H+ eq)

Respiratory Effects(kg PM10 eq)

EutrophicationPotential(kg N eq)

Smog Potential(kg O eq)

2

268 150

R e s u l t s N o r m a l i z e d t o

p e r C a p i t a ,

U S ,

Y e a r E m i s s i o n s

i n 1 9 9 9

3

NB: CS = carbon sequestration; NG = natural gas

*Normalization values or ossil uel consumption rom World Bank (2012).

**Normalization excludes long-term emissions (>100 years) rom landfill degradation.

Figure 2Results normalized to total U.S. results rom 1999 using data rom Bare, Gloria & Norris (2006)

With the growing importance o global warming in environmental discussions, it is useul to discuss the carbonaspects o this analysis. Te LCA study to be published by FPInnovations in 2013 will discuss the concept o a

potential carbon offset value or CL substitution. A carbon offset is also known as greenhouse gas displacement;it reers to the greenhouse gas emissions avoided by choosing an alternate practice over standard practice. Mid-

rise buildings in uébec are not typically made with wood systems, thereore the use o wood in that application would be considered an alternate practice. In that context, i CL results in reduced greenhouse gas emissionscompared to standard practice, one could quantiy the greenhouse gas displacement. Such a displacement is a

permanent and cumulative benefit or climate change mitigation.

Carbon storage is an important attribute o long-lived wood products like structural components. Te carbonin wood comes rom carbon dioxide which was removed rom the atmosphere by the tree as it grew. While thiscarbon returns to the atmosphere over the long term, completing the natural carbon cycle, the temporary storagein wood products allows additional CO

2 to be removed rom the atmosphere during the building lietime through

the re-growth o trees. Wood products are not a permanent greenhouse gas removal mechanism; however, thetemporary carbon storage in wood products can be reasonably considered a carbon credit, depending on timerame and end-o-lie assumptions. Tis reasoning largely stems rom the current urgency around climate change,

where any delay in carbon emission is helpul in “buying time” to find mitigation solutions to climate change.

For traditional wood structural systems, the carbon mass o wood is relatively small compared to the carbonemissions avoided by using wood instead o steel or concrete (Sathre, O’Connor, 2010). Tereore, an importantocus in the use o wood to combat climate change is to increase our rate o wood substitution or other materials,

with less emphasis on carbon storage. With CL, the relationship is the opposite: the carbon mass o wood isquite large compared to the avoided emissions o alternate materials. In this case, there is an interest in putting a

value on that stored carbon, with a motivation to keep the carbon in service or as long as possible, and to capturethe energy value o that carbon to replace ossil uel at the end o service lie. In total, the wood content o the


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modeled CL building equates to about 951 metric tons o CO2. o put this amount in context, 951 metric tons

o CO2 are emitted in one year o driving 186 cars4.

It is important to recognize that the carbon profile o wood construction and any claimed carbon benefits rely on

an assumption o sustainable orest management, such that long-term carbon stocks in orests do not decline dueto the use o wood products; see the section on orest resource implications o CL or discussion on that topic.In addition, note that carbon accounting with regards to wood and orestry is complex, as urther discussed inAppendix B.

As a preabricated product, CL has good potential or recovery at the end o a building’s service lie or use inanother building. Reusing CL panels reduces GWP by 263 metric tons o CO

2 equivalent when the end-o-lie

scenarios include landfilling by reducing production and transport emissions and prolonging the release o storedcarbon to the atmosphere.

4 Conversion to cars was calculated using the U.S. EPA Greenhouse Gas Equivalencies Calculator,http://www.epa.gov/cleanenergy/energy-resources/calculator.html.


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In this section, we provide preliminary findings regarding emissions to indoor air rom cross-laminated timber.Tis data applies to CL made rom two Canadian wood species, which is the only North American CLcommercially available at the time o this writing. Note that wood product emissions are species-specific, andthese test results may not apply to products made rom different manuacturers.

As regulatory and non-governmental organizations (NGOs) address indoor air quality issues, they tend toocus on volatile organic compounds (VOCs), including ormaldehyde, as key actors relating to the discomortreported by people working or living inside “air tight” buildings. For wood products, VOCs and specificallyormaldehyde are o interest in products containing adhesives, which can be associated with emissions.

In this work, CL samples were examined or VOC emissions in the FPInnovations laboratory, ollowing

applicable test method standards. Please see Appendix C or details on the test methods and the results.

Five CL products were tested or their volatile organic compounds (VOCs), including ormaldehyde andacetaldehyde emissions. Te tested laminated products had different thicknesses and different numbers o gluelines. Emissions were collected afer 24 hours o samples exposure in the environmental chamber. Te adhesiveused to manuacture the CL products was a polyurethane glue (Purbond HB E202), while polyurethaneAshland UX-160/WD3-A322 glue was used or finger jointing.

Results did not show any correlation between individual VOCs (iVOCs), including ormaldehyde andacetaldehyde, or total VOCs (VOCs) and the thickness o the cross-laminated timber panel or the number oglue lines. All five products showed very low levels o iVOC (the highest level was observed with alpha-pinene and340 µg/m or VOC emissions); most o the detected VOCs consisted o terpene compounds that are naturallyound in the wood material itsel. Tereore, it can be concluded that the CL tested will have a negligible or zero

impact on indoor air quality.

Te ormaldehyde emission limits set orth by the Caliornian Air Resource Board (known under the acronymCARB Phase I and Phase II) are some o the most rigorous emission limits in the United States or woodcomposite products and have been in effect since July 1st, 2012. Results reported here show that the CL samplestested easily meet the most stringent CARB limits.

In addition, the results or the five samples were generally lower than limits set orth by European emissionlabeling systems. In act, the 24-hour CL test results were lower than European limits intended or measurementafer three days.

Please see Appendix C or details and urther results.

3POTENTIAL INDOOR

AIR QUALITY IMPACTSOF USING CLTIN BUILDINGS


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When compared to traditional light-rame construction, CL may appear to be at odds with one o thecornerstones o sustainable design—the efficient use o materials—potentially increasing the volume o wood usedin a project substantially. We will discuss the topic o material efficiency later in this Chapter. In this section, wediscuss the ability o North American orests to accommodate the use o a product that appears to consume a largeamount o wood.

raditionally, designers have relied on heavy construction materials such as concrete tilt up, steel rames,and composite decking systems to achieve a solid structure with large spans and tall plate heights. Anecdotalinormation rom the WoodWorks5 team suggests that designers are increasingly considering the use o a timberalternative because o their perception that timber has carbon benefits when substituted or other materials and arelatively small manuacturing energy input; however, some have questioned whether an increase in demand or

lumber will negatively impact our orest resources. I designers in the United States begin to replace constructionmaterials typically used in commercial buildings with mass timber products such as CL, will we create anunsustainable trend leading to orest resource depletion?

Te answer is no. Stringent sustainable orest management practices in the United States and Canada restrictharvesting levels (while additionally maintaining other orest values such as biodiversity and wildlie habitat). Still,CL users may wonder i a major uptake o CL would be elt in the orest. In this Section, we use market datato demonstrate hypothetical scenarios; we show how many CL buildings can easily be accommodated withinhistoric sustainable supply capacity. Note that we do not address the availability o CL; many other productscompete or orest resources. In this exercise, we simply put theoretical CL consumption in the context o currentconstruction wood usage in order to provide a sense o magnitude o the potential impact o CL.

In Chapter 1 o this Handbook, an assessment o the market opportunity or CL was completed whereby the

estimated 2015 volume o new construction was overlaid by market segment with the scenarios o CLcapturing both 5% and 15% o that new construction market. I CL was used or 15% o new multi-residentialand non-residential construction projects (1 to 10 stories) built in 2015, there would be a 12% increase in theoverall board ootage demand over 2011 levels. o put this in perspective, in 2011 the estimated U.S. lumberconsumption was 22.6 billion board eet (BBF) (RISI), while in 2005, when the United States was at its peak orlumber demand, it is estimated that 45.5 BBF (RISI) was consumed—a difference o 186%. For the lumber market

4RESOURCE

ASSESSMENT:IMPACT OF CLTON THE FOREST

5 WoodWorks is an initiative o the Wood Products Council established to provide ree technical support as well as education and resourcesrelated to the design o non-residential and multi-amily wood buildings.


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to see 2005 levels o demand based on the construction expectations or 2015, CL would have to comprise over100% o the multi-residential and non-residential market.6

Potential impact on total consumption can be explored deeper in the context o a prototypical CL building. Te

Stadthaus project in the United Kingdom is an eight-story, 24,000 square oot CL structure, built over one storyo concrete with 29 residential units and an office. Tis structure is one o the tallest modern timber structures inthe world and includes an estimated 33,500 cubic eet (950 cubic meters) o timber (Waugh, 2009).

CL is not currently being commercially produced in the United States or structural purposes, however domesticinterests are high and the U.S. wood industry anticipates some local production by 2015. As such, it is pertinent toexplore the effects o CL use on U.S. orests. In 2006, 9.86 billion cubic eet o sofwood lumber was harvestedrom U.S. orest lands, which means the lumber harvested or wood products in 2006 in the United States alonecould build over 295,000 CL structures equivalent in volume to the Stadthaus project or 7.06 billion square eeto CL projects with equivalent density (cubic eet o timber/square oot o floor area).7

While the Stadthaus example may seem irrelevant because CL construction would not replace current woodconstruction but rather represent additional demands, let’s put this in another context. Te 2012 demand or

wood products is down more than 45% (RISI) rom 2006 levels. Consider that, in addition to domestic supply,the United States imports on average 25-33% (RISI) o its wood supply rom Canada. Because we know that the2006 level o production did not adversely affect the domestic or Canadian standing inventory, it is plausible that,based on orecasts or 2012 U.S. construction, North American orests could accommodate over 176,696 CLstructures equivalent in volume to the Stadthaus project (or 4.24 billion square eet) in addition to the currentdemands or light-rame wood products.8

North American orestry has a proven record o maintaining the standing orest. Figure 3 shows the growth-removal ratios (growth/harvest) or U.S. orests in recent history. Since 1952, the growth-removal ratios orboth sofwood and hardwood demonstrate that growth has exceeded harvest and the United States has not beendepleting its orest resources rom a timber volume standpoint, even during periods o high demand. In 2006,

when 1.7% o the standing volume o the orest was harvested (Smith et al., 2009; able 17) and the United States produced 45.5 BBF o lumber (RISI), orest growth still exceeded harvest by close to 1%.

6 As previously noted, there are many end uses or orest resources, all o which may compete or a finite supply o raw materials depending

on market economics. Should U.S. housing starts ever return to 2005 peak levels and thereby once again create a large demand or raminglumber, restricted supply o raw resources and the resulting effect on market prices may affect the availability o raw resources or CL

production. Te current example is not meant to suggest that enough CL would necessarily be available or building 100% o all multi-residential and non-residential buildings.

7 Again, this example is simply provided to convey a concept o scale, and to illustrate the vast number o CL buildings that could be erectedi all lumber supply were directed to this use.

8 Calculated based on the ollowing:• Volume o sofwood lumber harvested in the United States in 2006 = 9.86 x 109 f.3 • Estimated total volume o North American lumber consumed in 2006 (based on 25% historical Canadian imports) = 13.15 x 109 f.3 • Estimated volume o sofwood lumber harvested in the United States in 2012 = 5.42 x 109 f.3 • Estimated total volume o North American lumber consumed in 2012 (based on 25% historical Canadian imports) = 7.23 x 109 f.3 • Estimated volume o CL in Stadthaus project = 33,500 f. 3 • CL Plan Square ootage o Stadhaus project = 24,000 f.2 • Estimated additional capacity available = (13.15 x 109 f.3 – 7.23 x 109 f.3)/33,500 f.3= 176,696 Stadthaus equivalent structures• Estimated additional demand capacity available = 176,696 structures x 24,000 f.2/1structure = 4.24 x 109 f.2


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1952 1962 1976 1986 1996 20060.0

0.5

1.0

1.5

2.0

2.5

3.0

Year

Softwoods

Hardwoods

Total

G r o w t h - r e m o v a l R a t i o

Figure 3Growth-removal ratios by sofwoods and hardwoods, 1952-2006 (Data source: Smith et al., 2009)

Overall, orest standing inventory is affected by more than growth and removal. Forest mortality due to insect,disease and fire also needs to be taken into account. While the mortality rate has been steadily increasing, theoverall rate o loss remains less than 1% o the growing stock. Tis means that the overall standing inventory osofwood and hardwood continues to grow even with harvest and natural mortality actored in. Because CL hasthe ability to utilize lower grade dimensional lumber, it also offers an opportunity to utilize a large percentage oorests devastated by insect and disease. CL offers the possibility or the standing dead wood in such orests tobe used in a high value product, financially incentivizing the use o what would otherwise be considered a wastedresource, provided the trees are accessible and near a mill.

Users o any wood products including CL can be confident that North American orest practices comply with

strict harvesting controls. Numerous government and industry publications provide detailed data on an annualbasis or the purpose o transparent disclosure to the public about orests, harvesting and orest management.According to “Sustainable Forestry in North America”, a pamphlet that concisely summarizes this data, “there are alarge number o ederal policies covering U.S. orests, and the State and local legal requirements are also extensive.During the past 50 years, less than 2 percent o the standing tree inventory in the U.S. was harvested each year,

while net tree growth was 3 percent.” Note that a portion o wood used in U.S. construction comes rom Canada.“In Canada, 93 percent o the orests are publicly owned and orest companies operate under some o the moststringent sustainability laws and reg ulations in the world. Less than one hal o one percent o the managed orestis harvested annually, and the law requires all areas to be promptly regenerated.”9

Worldwide, only 10 percent o orests are certified to one or more sustainable orest certification standards. Tesestandards tend to have more similarities than differences and, while there are those who debate the merits o oneover another, the real issues o concern—such as deorestation and illegal logging—are occurring in orests thatare not certified and located in developing countries with insufficient laws and governing structures to ensuresustainable orest management.

9 For these orestry statistics and more inormation on orest practices in the United States and Canada,see “Sustainable Forestry in North America”, available at www.woodworks.org


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As o August 2012, more than 500 million acres o orest in Canada and the United States were certified underone o the our internationally recognized programs used in North America: the Sustainable Forestry Initiative(SFI), Canadian Standards Association’s Sustainable Forest Management Standards (CSA), Forest StewardshipCouncil (FSC), and American ree Farm System (AFS), accounting or approximately 29% o North American

orests (SFI, personal communication) (Figure 4). In the United States, the majority o non-certified orests aresmall (


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In green building programs, there are currently limited incentives that would directly encourage the use o CLon environmental merits. Some direct and indirect green building motivations relevant to CL might include:

• Renewable materials: as a wood material, CL is renewable. Forest practices in North America are typicallyaligned with sustainable orest management principles, ensuring that wood is renewed. CL consumption

will not overly burden the sustainable supply capacity o North American orests as demonstrated in the previous section.

• Local materials: CL is manuactured in North America and potentially can be sourced within a radiusdeemed “local,” depending on the definition o local, location o final installation, and the possible utureemergence o more manuacturers than the two currently in operation at the time o this writing (bothare located in Canada).

• Certified wood: CL manuacturers can obtain chain-o-custody certification or sustainableorestry management.

• Carbon storage: i incentives should emerge or the value o the carbon stored or decades in buildings,CL might have a market advantage over other structural systems.

• Carbon offsets: i incentives should emerge or the value o the greenhouse gas emissions avoided when usingCL in place o other materials with a higher greenhouse gas ootprint (in other words, a carbon offset), CLmay experience market advantage.

• LCA used during building design: a number o design guidelines or green design such as the CaliorniaGreen Building Standards Code, the International Green Construction Code, Green Globes® and LEED®10 contain possible motivators or designers to use lie cycle assessment during the design process with the goalthat they produce buildings having minimal LCA impact. Previous literature suggests that CL systems have

lower LCA impacts than alternative systems (see literature review in Appendix A).• EPD credits: at the time o this writing, the draf o LEED v.4, anticipated or release in summer 2013,

includes a Materials and Resources credit or designers to select products that have published environmental product declarations (EPDs) or have a published manuacturer-specific cradle-to-gate LCA study. In addition,at the time o this writing, LEED has a pilot credit or EPDs and manuacturer-specific LCAs. At this time,the two North American manuacturers o CL (Structurlam and Nordic) have LCA reports and aredeveloping EPDs.

5POTENTIAL

CONTRIBUTIONOF CLT TO GREENBUILDING OBJECTIVES

10 LEED Pilot Credit 63 (in place as o this writing; uture status unknown given the pending arrival o LEED v.4) provides an incentive ordesigners to use whole-building LCA to show improvement o a final design over a reerence building. Tis credit, in a s lightly different orm,is a new credit proposed or LEED v.4 (the 5th comment period version).


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• Health, comort and well-being benefits: Occupants exposed to wood have shown benefits in their well-being[Fell, 2010]; CL—i lef exposed—may contribute to a health and comort objective. CL does not adverselyaffect indoor air quality, as shown in the previous section.

• Reusability: As a panelized system, CL has good potential or disassembly and reuse. Realizing this potential

will require development o construction details or disassembly and the inrastructure to transer productsto a new site.

• Operating energy savings: CL is a massive material with some thermal mass; thermal mass is ofenidentified as a contributor to overall savings in a building’s heating and cooling loads and/or costs due to peakload shifing.

• Efficient use o resources: As a preabricated product, CL has minimal construction site waste, andconstruction time is shortened. Waste created at the time o manuacture is minimized by automationand can be ed back into the manuacturing plant’s biouel plant or use as carbon neutral energ y.

Material efficiency is an important sustainable design objective that requires discussion with respect to CL.CL buildings are massive, which is an unusual use o wood rom the North American light-rame perspective.At first glance, CL may appear wasteul, i we are comparing CL to light-rame wood.

However, the distinction between light-rame and “heavy” construction is important in the assessment oefficiency and a key element in determining the environmental benefits o CL. For example, when light gaugemetal is compared with heavy steel braced rames, the question o material efficiency probably doesn’t arise.Tis is because most architects and engineers understand that there is a difference in application and required

perormance or each o these structural systems.

Te intent o CL is not to replace light-rame construction, but rather to offer a low-carbon alternative to“heavy” construction materials such as concrete and steel. Tere are building applications where light-rameconstruction is less appropriate, such as an industrial warehouse with 40’ walls that need to withstand the impactso heavy machinery, or a Class A office building where ew partition walls and minimal floor vibrations aredesired. raditionally, designers have relied on heavy construction materials such as concrete tilt up, steel rames

and composite decking systems to achieve a solid structure with large spans and tall plate heights. oday, moredesigners are considering the use o a timber alternative.

When CL is properly considered within the context o heavy construction systems, it can be an efficient use o wood. Nonetheless, every construction system should be designed or maximum efficiency, and there are methodsor maximizing the effectiveness o CL systems. For example:

• Optimize span capabilities. Whether it is tailoring a design to meet the maximum span o a specific CL product or optimizing the layup to meet the demands o the design, designers and manuacturers should worktogether to maximize utilization o CL’s structural capacity. Final CL shop drawings and design are doneby the manuacturer and each manuacturer will differ in their panel dimensions, lamination thicknesses,connections, wood species and preerred layout configurations. For this reason, it is important to engagethe preerred abricator early in the design process i some o these actors are critical or architectural or

other requirements.• Optimize the openings. When the panel layouts are established or a design, use beams over doorways and

place windows in between ull size panels to avoid waste that might be created i a ull panel was used withcut out openings. Using more ull sized panels also allows more versatility to reuse the panels later in the

product liecycle.


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Both o these strategies may be initiated by CL manuacturers in order to reduce costs. Tere are also moreelaborate ways or designers to ensure efficient use o CL:

• Use folded diaphragms. Tis is a sophisticated technique used with other heavy construction materials that

enables CL panels to span greater distances without increasing the wood fiber needed in the lamination. Aolded plate design borrows stiffness rom the out-o-plane diaphragm to increase the moment o inertia orstiffness o an assembly by increasing the effective distance between the extreme fibers in the bending plane.Connection design at the old is critical but the load can be distributed along the entire joint instead oconcentrated at discreet points.

• Employ 3D structural analysis techniques. CL structures have the ability to act in three dimensions. Similarto a olded diaphragm, the cube effect takes advantage o CL’s ability to transer load in all three axis in thesame panel. A single CL panel can take a vertical axis load anywhere in the plane o the panel, lateral shearload in the other axis o the same plane, and a bending load into the ace o the panel and transer the resultingshear in a third axis. Tereore, including a structural analysis that takes advantage o this cube effect mayreduce the amount o material required in the overall structural design.

• Account for disaster resilience capabilities. In the world o sustainable design, the concept o disaster

resilience is only going to become more prominent. Tere is a considerable advantage to having a building withthe ability to quickly return to operation afer a disaster and in the process minimizing the lie cycle impactsassociated with its repair. Based on the ull scale seismic testing discussed in Chapter 4 entitled Lateral design ocross-laminated timber buildings, CL structures may offer more disaster resilience than those built with otherheavy construction materials. Because ailures are designed to happen at the connections, the test buildingsuffered isolated and minimal structural damage even afer 14 consecutive shake table tests. Assuming the sameresults or an actual building, the rehabilitation and repair required ollowing an earthquake would also beminimal.


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Cross-laminated timber contains only two materials: lumber and adhesive. For the two North American CLmanuacturers in commercial production at the time o this writing, lumber is locally sourced (maximumtransportation distance 329 miles/530 km) and comprises a ew sofwood Canadian species. wo adhesives

are used: polyurethane and arclin melamine.

6MATERIAL DISCLOSURE


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In this Chapter, we assessed several attributes o CL to determine i this product could be a contributor togreen building objectives. Our conclusion is yes, CL meets many criteria designers might be looking or whenspeciying materials or sustainable construction.

In particular, the use o wood in buildings prior to using the wood to produce energy offers clear advantages.As reported in numerous other studies11, wood products typically contain more carbon than is emitted duringharvest, manuacturing, transportation and end-use. Tis carbon was removed rom the atmosphere when theliving tree absorbed the greenhouse gas carbon dioxide. Based on our preliminary results, a significant portion omaterial-related greenhouse gas emissions rom a CL building in uébec are offset by the carbon storage benefitso wood and the potential or substituting ossil uel energy sources with wood at the end o the building lie.

From an environmental standpoint, carbon storage benefits involve a delayed greenhouse gas emission during thetime that orests re-grow and re-sequester carbon; the carbon storage in wood products is temporary as the carbon

will eventually return to the atmosphere, and, thereore, over a long time rame, has no effect on global carbonbalances. However, a carbon-balance does not equal climate-neutral and delayed emissions rom the storage o

wood products provide quantifiable benefits or avoiding atmospheric warming over the short term (~100 yearsor so), as demonstrated by our results, that diminish over extended time horizons (Guest, Cherubini & Strømman,2012).12 Based on the urgent need to reduce greenhouse gas emissions in the short term to avoid “dangerousanthropogenic intererence with the climate system” — internationally recognized as a global temperature changeo more than 2°C (UNFCCC, 2010, p. 5) — the avoided GWP rom using wood products in buildings presentsan opportunity to contribute to short-term emissions reductions.

Te carbon stored in wood products in long-term use such as construction is a substantial carbon pool which would be increased with the use o CL. Tis product might help extend the timeline or this stored carbon,as CL panels may be good candidates or recovery at the end o building lie, or reuse in another building.

7CONCLUSIONS

11 For example, see the 40 papers reviewed in Werner, F. and Richter, K, 2007, Wooden building products in comparative LCA: A literaturereview; International Journal o Lie Cycle Assessment, 12(7): 470-479; and the 66 papers reviewed in Sathre, R and O’Connor, J, 2010,A Synthesis o Research on Wood Products and Greenhouse Gas Impacts, 2nd Edition, FPInnovations.

12 For a 100 year rotation period, Guest et al. (2012) show that 1 kg o wood products stored or 60 years has a GWP using a 100 year timerame o around -0.07 kg CO

2 eq, when incinerated at year 60, vs. a GWP using a 500 year time rame o -0.01 kg CO

2 eq.


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ASM International. 1996. Standard test method or determining ormaldehyde concentration in air om wood products using a small-scale chamber . ASM D6007-96. West Conshohocken, PA: ASM. 8 p.

______. 2002. Standard test method or determining ormaldehyde concentrations in air and emission rates omwood products using a large chamber . ASM E1333-96(2002). West Conshohocken, PA: ASM. 12 p.

______. 2003. Standard test method or determination o ormaldehyde and other carbonyl compounds in air(active sampler methodology). ASM D5197-03. West Conshohocken, PA: ASM. 15 p.

______. 2006. Standard guide or small-scale environmental chamber determination o organic emissions om indoor materials/products. ASM D5116-06. West Conshohocken, PA: ASM. 15 p.

Athena Sustainable Materials Institute. 2009. A cradle-to-gate lie cycle assessment o Canadian sofwood lumber .Ottawa, ON: Athena Sustainable Materials Institute.

Athena Sustainable Materials Institute. 2012a. Impact estimator . Retrieved July 12, 2012, romhttp://calculatelca.com.

Athena Sustainable Materials Institute. 2012b. Liecycle assessment o cross-laminated timber produced at Nordic Engineered Wood Products. Ottawa, ON: Athena Sustainable Materials Institute.

Bare, J. 2011. RACI 2.0: Te tool or the reduction and assessment o chemical and other environmentalimpacts 2.0. Clean Technologies and Environmental Policy 13 (5):687–696. doi:10.1007/s10098-010-0338-9.

Bare, J., . Gloria, and G. Norris. 2006. Development o the method and U.S. normalization database or LieCycle Impact Assessment and sustainability metrics. Enironmental Science & Technology, 40 (16):5108–5115.doi:10.1021/es052494b.

Barry, A. 1995. Measurement o VOCs emitted rom particleboard and MDF panel products supplied byCPA mills: A report by Forintek Canada Corporation or the Canadian Particleboard Association. uebec,QC: Forintek. 20 p.

Barry, A., and D. Corneau. 1999. Volatile organic chemicals emissions rom OSB as a unction o processing parameters. Holzorschung 53:441-446.

Barry, A., D. Corneau, and R. Lovell. 2000. Press volatile organic compounds emissions as a unction o wood processing parameters. Forest Products Journal 50 (10):35-42.

8REFERENCES


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cycle and albedo dynamics in lie cycle impact assessment. Enironmental Impact Assessment Review 37:2–11.doi:10.1016/j.eiar.2012.01.002.

Cherubini, F., G.P. Peters, . Berntsen, A.H. Strømman, and E. Hertwich. 2011a. CO2 emissions

rom biomass combustion or bioenergy: Atmospheric decay and contribution to global warming.GCB Bioenergy 3 (5):413–426. doi:10.1111/j.1757-1707.2011.01102.x.

Cherubini, F., A.H. Strømman, and E. Hertwich. 2011b. Effects o boreal orest management practices onthe climate impact o CO

2 emissions rom bioenergy. Ecological Modelling 223(1):59–66. doi:10.1016/j.

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Commission o the European Communities. 1989. Formaldehyde emission om wood based materials: Guideline or the determination o steady state concentrations in test chambers. Report no. 2 o EUR 12196 - European

concerted action: Indoor air quality and its impact on man. COS Project 613. Brussels, Luxembourg: Officeor Official Publications o the European Communities. 24 p.

Fell, D. 2010. Wood in the human environment: Restorative properties o wood in the built indoor environment.PhD diss., University o British Columbia. 134 p.

Gagnon, S., and C. Pirvu, eds. 2011. CLT handbook: Cross-laminated timber . Canadian ed. Special PublicationSP-528E. uebec, QC: FPInnovations. 1 v.

Guest, G., F. Cherubini, and A. H. Strømman. 2012. Global warming potential o carbon dioxide emissionsrom biomass stored in the anthroposphere and used or bioenergy at end o lie. Journal o Industrial Ecology doi:10.1111/j.1530-9290.2012.00507.x.

Gustavsson, L., A. Joelsson, and R. Sathre. 2010. Lie cycle primary energy use and carbon emissiono an eight-story wood-ramed apartment building. Energy and Buildings 42 (2):230-242.

Intergovernmental Panel on Climate Change (IPCC). 2006. Solid waste disposal. Chapter 3 in Waste, vol. 5 o 2006 IPCC guidelines or national greenhouse gas inventories. Retrieved rom http://www.ipcc-nggip.iges.or.jp/ public/2006gl/vol5.html.

John, S., B. Nebel, N. Perez, and A. Buchanan. 2009. Environmental impacts o multi-storey buildings usingdifferent construction materials. Research Report 2008-02. Christchurch, New Zealand: University oCanterbury, Department o Civil and Natural Resources Engineering. 135 p.

Kostiuk, A.P., and F. Paff. 1997. Conversion actors or the orest products industry in eastern Canada.

Sainte-Foy, QC: Forintek Canada Corp., Eastern Division.

Levasseur, A., P. Lesage, M. Margni, L. Deschênes, and R . Samson. 2010. Considering time in LCA: DynamicLCA and its application to global warming impact assessments. Enironmental Science & Technology 44 (8):3169–3174. doi:10.1021/es9030003.

Levasseur, A., P. Lesage, M. Margni, and R. Samson. 2012. Biogenic carbon and temporary storage addressed with dynamic lie cycle assessment. Journal o Industrial Ecology. doi:10.1111/j.1530-9290.2012.00503.x.


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Mahalle, L., J. O’Connor, and A. Barry. 2011. Environmental perormance o cross-laminated timber.Chapter 11 in CLT handbook: Cross-laminated timber . Canadian ed. uébec, QC: FPInnovations. 1 v.

Malmsheimer, R.W., J.L. Bowyer, J.S. Fried, E. Gee, R .L. Izlar, R.A. Miner, I.A. Munn, et al. 2011. Managing

orests because carbon matters: Integrating energy, products, and land management policy. Journal o Forestry 109 (7S):S7–S51.

McKeever, D.B., C. Adair, and J. O’Connor. 2006. Wood products used in the construction o low-rise nonresisdentialbuildings in the United States, 2003. acoma, WA: Wood Products Council. 63 p.

Meil, J., M. Lucuik, J. O’Connor, and J. Dangerfield. 2006. A lie cycle environmental and economic assessmento optimum value engineering in houses. Forest Products Journal 56 (9):19-25.

Micales, J.A., and K.E. Skog. 1997. Te decomposition o orest products in landfills. International Biodeterioration & Biodegradation 39 (2-3):145–158. doi:10.1016/S0964-8305(97)83389-6.

Muter, D., and J. O’Connor. 2009. Market and GHG assessment o new wood applications.

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A1 Literature Review on Environmental Perormance o CL

Tere is very little existing LCA data or validated comparative studies addressing CL. Several promotional pieceson the mid-rise Stadthaus building in England make comparative assertions about CL, but these lack supportliterature, clarity and methodological accuracy.

Gustavsson et al. (2010) perormed a ull lie cycle assessment o energy use and greenhouse gas emissions or aCL mid-rise building in Sweden (part o the Limnologen project). Energy use and carbon flows are tracked alongthe entire chain and include carbon stocks in building products and avoided ossil uel combustion emissions

where biouel residues are used as a substitute energy source or ossil uel. Te authors argue that a major carbonbenefit or this wood-intensive building is the side effect o using wood residues as an energy substitute orossil uel. Te biouel can be collected in the orm o harvesting residues, wood manuacturing residues,and—eventually—the CL panels themselves at the end o their useul lie.

Robertson (2010, 2012) conducted a comparative LCA study on a five-story office building made o concrete

versus a CL and glulam hybrid building, using a lie cycle inventory rom primary data gathered at a CL pilot plant in British Columbia. Results indicate a lower environmental impact or the glulam/CL building over theconcrete building in nine out o eleven environmental indicators.

A mid-rise LCA study by John et al. (2009) could provide a comparative basis or examining the CL resultsin the Swedish study. Tis New Zealand study perormed ull LCA or our different structural approaches to asix-story office building (concrete, steel, and two different wood versions). While results rom the New Zealandstudy are not directly comparable to those o the Swedish study, we can potentially draw general conclusionsabout the likely comparative results or CL. It is useul to look at the two versions o wood buildings in the NewZealand study. One used a airly conventional quantity o structural wood while the other (called “timber plus” bythe authors) increased the use o wood in that model by assuming wood substitution or additional products suchas windows, ceilings and exterior cladding. Te study ound that total lie cycle energy consumption and carbonootprint both decrease as the use o wood increases. A similar examination was perormed by Meil et al. (2006)

with similar results. In both studies, the reason or this benefit is the substitution o wood or non-wood materialsthat have a heavier energy/greenhouse gas ootprint.

APPENDIX ALITERATURE REVIEW


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In the New Zealand study, various end-o-lie scenarios were examined and operating energy was included; theseare two important actors to consider when properly comparing wood to other materials in construction. In thisstudy, thermal mass in the buildings was accounted or in the energ y modeling, and the concrete building hadthe lowest operating energy consumption. However, this was overtaken by the embodied energy savings o the

“timber plus” version over the concrete version due to product substitution. For the end-o-lie landfilling scenario,the authors also contend that a significant portion o the carbon contained in the wood materials is stored permanently, giving both wood versions o the building lower total lie cycle carbon ootprints than the steel andconcrete versions. Te “timber plus” version has a substantially lower total carbon ootprint than the other wood

version due to embodied energy savings in product substitution, lower operating energy consumption due tothermal mass, and a greater mass o wood carbon in permanent landfill storage.

From this study, we can perhaps orm a hypothesis about likely comparative perormance o CL. I we assumethat CL has a smaller manuacturing carbon ootprint than concrete and that all other lie cycle actors aresimilar to the “timber plus” model, it would ollow that a CL version would perorm similarly or perhaps betterthan the “timber plus” model, given that it would have more wood mass available or permanent landfill storageat end o lie.

In the Canadian edition o the CL Handbook, a hypothetical LCA comparison was conducted (Mahalle et al.,2011). Glulam was used as a proxy or CL, as no LCA data was available at that time. CL was compared toconcrete unctional equivalents in the context o a mid-rise building and in the context o a floor. In both cases,the CL option showed lower results in all impact measures and resource consumptions addressed in the study.


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B1 Objective and Method

Te objective o the work reported here is to provide preliminary findings rom an environmental lie cycleassessment (LCA) o a 43,700 square oot, our-story (plus one underground level) CL apartment building.

LCA is a ISO 14040/14044 (2006; 2006) standardized tool used to evaluate the environmental perormanceo a product, service or system.13 It involves evaluating the energy and material inputs, as well as wastes thatare produced, throughout the supply chain and end-o-lie disposal o a product. LCA is useul or identiyingenvironmental hot-spots along the supply chain, or avoiding problem shifing where one environmental problemis ‘solved’ by shifing the environmental burdens in time or space rom one phase o a product liecycle to another

phase, and or highlighting trade-offs between different environmental indicators.

Engineering and architectural drawings or an existing our-story CL apartment building in Chibougamau,uébec, are used to create a detailed bottom-up material inventory or this assessment. Te building lietime isassumed to be 60 years. Te Athena Impact Estimator is the building LCA tool adopted or this analysis. Te

Impact Estimator uses regional inormation in its calculations; uébec City was chosen as a location because itis the Impact Estimator predefined location closest to Chibougamau where the actual building is located.

As the results rom this study are intended or use in a comparative building assessment to be released byFPInnovations in 2013, building elements that were known or assumed to be identical were excluded. Toseinclude: enestration, exterior cladding, flooring, HVAC, hand railings, plumbing and electrical equipment, etc.

Te system boundary describes the phases o the building liecycle included in the analysis. Tese are: resourceextraction and material production, construction, maintenance and replacement, demolition, and associatedtransport processes (see Figure 5). Building operation was assumed to be equivalent and excluded romthe analysis. Further exclusions due to a lack o data included architectural and engineering services, and

worker transport.

APPENDIX BDETAILS ON THE

MID-RISE LCA STUDY

13 Te terms product, system and service are used interchangeably throughout the rest o this Chapterand simply reer to the object o the LCA investigation.


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Material andEnergyExtraction

EnergyProduction

Recycling/Reuse

Transport

MaterialInputs

Engineering & Architecture

Services

WorkerTransport

BuildingConstruction

Maintenace andReplacement

Demolition

WasteManagement

BuildingOperation

4060 m , 60 yrsBuildingLifecycle

2

Incineration Landfill

Material andProduct

Manufacturing

ConstructionWaste

BottomAsh

Excluded from model

Reference flow

Figure 5System boundary

Data collection or LCA involves developing a lie cycle inventory (LCI) or all material, energy and service inputsand outputs o the system. When describing data requirements or a LCA, it is useul to distinguish between theoreground system, what is explicitly modeled, and the background system, which relies on secondary data sources.

Te oreground system or this particular system was developed through detailed, bottom-up material estimatesor a residential CL building. An overview o the LCI developed or the oreground system is presented below.

Te main sources or background data are embedded in the Athena Impact Estimator (v4.2.0130 (AthenaSustainable Materials Institute, n.d.)). Te Impact Estimator includes the Athena Institute’s regional, NorthAmerican LCI database or building products, as well as energy and transport LCI data rom the USLCI database.

Additionally, the Impact Estimator includes estimates or transportation requirements, construction wastecoefficients, construction effects, maintenance and replacement activities, and end-o-lie treatment.A final important source o background data included cradle-to-grate LCI data or the manuacture o CLin Chibougamau, uébec, over 310 miles (500 km) north o uébec City (Athena Sustainable MaterialsInstitute, 2012b).


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Te impact assessment methodology and impact categories adopted or this assessment are a subset o theU.S. EPA’s ool or the Reduction and Assessment o Chemical and Other Environmental Impacts (RACI) 2.0(Bare, 2011), which is used by the Impact Estimator. Te RACI impact categories include:

• Global Warming Potential (GWP, measured in kg o CO2 equivalent)• Acidification Potential (AP, measured in moles o hydrogen ion (H+) equivalents)

• Respiratory Effects (RE, measured in kg o particulate matter (PM) up to 10 microns)

• Eutrophication Potential (EP, measured in kg nitrogen (N) equivalent)

• Ozone Depletion Potential (OD, measured in kg chlorofluorocarbon-11 (CFC-11) equivalent)

• Smog Potential (measured in kg o ozone (O3) equivalent)

Te Impact Estimator excludes RACI impacts or human toxicity and ecotoxicity, which are listed as optionalmeasures in ISO 21930 (2007) due to greater uncertainty in these measures. Fossil uel consumption is also anindicator category used by the Impact Estimator which reers to non-renewable ossil uel consumption pluseedstock ossil uel and includes direct and indirect energy use along the supply chain.

CL results rom the