Alternative structural systems - The C&S Companies · CNY Engineering Expo 3 Nov 2014. ... Finally, some alternative structural systems have significant benefits, including the potential

WHAT IF…

CARBON EMISSIONSOF STRUCTURAL SYSTEMS

MATTERED?Jim D’Aloisio, Klepper, Hahn & Hyatt

CNY Engineering Expo 3 Nov 2014

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© James A. D’Aloisio 2014

Copyright Materials

Klepper, Hahn & Hyatt Structural Engineering

315.446.9201 Landscape [email protected] Building Envelope Systems

Jim D’Aloisio, P.E., SECB, LEED AP BD+C

Yes, they matter. But we all act as if they don’t.

Traditional U.S. building’s structural systems are time-tested and reliable, but all have

drawbacks, regarding their environmental impact. One seldom-considered but

important aspect is the Carbon Dioxide Equivalent (CO2e) emissions generated by

their use. We will review the CO2e emissions of steel, concrete, masonry, and wood

construction, see how to reduce the emissions in practical ways, and what materials

to avoid completely. Many people think that the emissions of buildings over time due

to energy usage is large compared to the initial carbon emissions of construction.

This is usually not the case - it varies with construction type, envelope performance,

energy type, and the building’s service life. There is a methodology to determine

heating energy usage for a building system based on R-value, air-tightness, and

location. We will review this procedure, and then compare CO2e emissions from

construction to annual emissions due to heating energy, for various wall systems.

Finally, some alternative structural systems have significant benefits, including the

potential for reducing CO2e emissions in their construction and operation. These

include: Insulated concrete forms, structural insulated panels, straw bale

construction, and cross-laminated timber. For each, we will briefly review some

aspects of their usage as well as their CO2e emissions.

Course

Description

LEARNING OBJECTIVES

1. Calculate the CO2e emissions of various types of

structural systems.

2. Contrast the CO2e emitted during the construction

of building structure to the annual emissions due to

heating and cooling.

3. Recognize building materials that represent high

CO2e emissions.

4. Examine ways to reduce CO2e emissions from the

construction of concrete and steel structures.

At the end of the this course, participants will be able to:

Carbon Emissions of Structural Systems Page 5 of 60

GWP GASES

• Carbon Dioxide CO21 GWP over a 100 year period• 84% of US GWP gases emitted by humans, complex global cycle

• Methane CH4 21 GWP over a 100 year period• 9% of US GWP gases emitted by humans• Over 60% in atmosphere is emitted by human activities, globally

• Nitrous Oxide N2O 310 GWP over a 100 year period• 5% of US GWP gases emitted by humans,• Over 40% in atmosphere is emitted by human activities, globally

• Fluorinated Gases 140-24,000 GWP over 100 year period• Hydrofluorocarbons (HFC), Perfluorocarbons (PFC), Sulfur

Hexafluoride (SF6)• 100% emitted by human activities

GREENHOUSE GAS EMISSIONS BY CATEGORY

• Source: IPCC (2007); based on global

emissions from 2004


SEI SC CARBONWHITE PAPER

Structure and CarbonHow Materials Affect the Climate

AISC Structural Engineering Institute

(SEI) Sustainability Committee

www.seisustainability.org

Sustainability Committee –

Carbon Working Group

http://tiny.cc/SEIcarbon

http://www.seisustainability.org/

http://tiny.cc/SEIcarbon


OVERALL APPROACH

• CO2e “Pallet” – based on LCA data

• Tally of materials in wall system for 10-ft by 10-ft square section of wall

• Included 10-ft by 10-ft square section of concrete slab on grade and 10-foot long foundation wall and footing

• Calculated average R-values, BTU’s transmitted for Syracuse HDD’s, converted to average CO2e expended per year for heating


SCHEMATIC


HEATING ENERGY METHODOLOGY

• Syracuse - 6800 HDD ( Degrees F)

• Heating degree-days are the number of degrees that the daily average temperature falls below 65° F.

• Seasonal Heat Load = UA ∙ HDD ∙ 24 hours/day = 24 ∙ HDD ∙ A/R

• Assume 100% of heat is from natural gas

• 1 cubic foot of natural gas = 1,000 BTU of heat

• 1 cubic foot of natural gas = 0.12 lbs. CO2

∴ Annual lbs. CO2 emitted from heating 1sf of wall in Syracuse, NY

= 0.12 ∙ 6800 ∙ 24 ∙ 100 /1000 ∙ R = 2000/R (2 sig. figs.)(plus more due to heating system inefficiencies)

Cooling energy is “similar but different”


LIFE CYCLE ASSESSMENT(LCA)

• Tools available, or being developed

• EPA / NREL

• University of Bath – ICE

• Athena Impact Estimator

• BIM programs, especially Revit

• MIT, other

• Outcome highly dependent upon assumptions & variations, especially material source and composition, and life cycle assumptions

• Transparency is critical

• EPD’s – future source of verified data?


MY CO2 –E PALETTE *

• For Insulation:

• 100% of blowing agents included in tally

• XPS assumed HFC-134a

• For wood – value of carbon sequestration during its service life is not included

• Nominal amount of waste assumed

• Nominal worker travel assumed

* - AKA “emissions of admissions”


MY CO2 –E PALLET


MY CO2 –E PALLET


SNAPSHOT: JOBSITE LABOR

Hypothetical Labor Situation:

12 workers, driving 12 trucks that get 12 mpg, 12 miles to and from jobsite, for 12 weeks….

12 ⋅ 20 lbs. CO2/g/12 mi./g ⋅ 12 mi. ⋅ 12 ⋅ 5 =

14,400 lbs. CO2


DEMATERIALIZATION

• Definition: Using less or no material to deliver the same level of functionality

• Less material less environmental footprint

• Other things to consider:

• Reusability and Flexibility

• Resilience and Redundancy

• Serviceability


CONCRETE – GWP GAS EMISSIONS

• Production of Portland cement accounts for 6% to 8%* of the worldwide anthropogenic CO2

• About half is produced from the chemical reaction

• About half is released in the heating process - 2,700 degrees F

• 1 ton of Portland cement produces about 1 nearly 1 ton of CO2

* - the actual percentage is subject to debate Portland cement plant

in Alpena, MI


CONCRETE – GWP GAS EMISSIONS

• Highly dependent upon mix design

• Technically feasible does NOT mean readily available

• Construction• Idling construction vehicles, fuel, etc.• Labor intensive - worker travel

• HUGE potential for carbon reduction


CONCRETE EPD’S(Environmental Product Declarations)

Central Concrete

•1479 Mixes in 7 different service areas and 8 different

concrete plants in the San Francisco Bay area

•NRMCA-Certified EPD’s

•Parameters include GWP (kg CO2e per cubic meter)

•CO2e ranged from 346 to 810 lbs. per CY of concrete

http://centralconcrete.com/Central_Concrete_EPD.pdf

Also…http://www.nrmca.org/sustainability/EPDProgram/Downloads/

NRMCA%20EPD%2010.08.2014.pdf




FROST-PROTECTED SHALLOW FOUNDATIONS

• Strategically placed rigid insulation and drainage fill

• Reduces depth of excavation, backfill, foundation material

• Schemes for both heated and unheated buildings and elements

Source: National Association of Home Builders - www.nahb.com



• Industry-standard design guides available

• Required to be used by some large clients

• Can save money, time, and GWP gas emissions (in several ways)

• Watch the type of insulation used!

• Highly detail-sensitive



LEFT:

Conv. Ftg/fdn wall

Aconc = 7.5 sf/ft.

RIGHT: FPSF

Aconc = 2.6 sf/ft.

65% redux of conc!


VOIDED CONCRETE SLAB SYSTEM

photos courtesy Cobiax USA, Inc.

Hollow plastic spheres or shapes

Reduction of concrete volume and weight


REINFORCED CONCRETE WALLGWP GAS EMISSIONS

1775

131

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

10,000

Construction Annual Heating

Superstructure Wall

Slab on Grade

Foundation


MASONRY – GWP GAS EMISSIONS

• Material and component sources vary

• Ask about Portland cement content in CMU

• Possibilities: Fly Ash Brick, HVFA, slag block, …

• Consider SCM in grout – not proportion spec

• Construction

• Idling construction vehicles, fuel, etc.

• Labor intensive - worker travel

REDUCED-WEB CMUINSULATION SYSTEMS

New ASTM C90 allows smaller web areas than previously


UNREINFORCED MASONRYGWP GAS EMISSIONS

963

126

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

10,000


Superstructure Wall

Slab on Grade

Foundation


REINFORCED MASONRYGWP GAS EMISSIONS

1556

125

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

10,000


Superstructure Wall

Slab on Grade

Foundation


STEEL – GWP GAS EMISSIONS

• Different manufacturing methods

• Basic Oxygen Furnace

• Electric Arc Furnace

• Fabrication

• Construction

• Idling construction vehicles, fuel, etc.

• Labor intensive - worker travel

• Assumption of future reuse?


REUSED STRUCTURAL STEEL• A.K.A. “salvaged” steel

• Steel has no structural “memory”

• Frequently around 90% reduction of GWP emissions (from 1.0 to 0.1)

• May or may not save $

• Lessons to be learned

• Sourcing• Inspection• Preparation

• Where are the warehouses?


Steel Moment Frames

require more steel material

per service unit than

braced frames.

Braced frames can be

designed in a variety of

configurations.

Consider Hybrid

Masonry/Steel Frames.

STEEL LATERAL BRACING SYSTEMS


COLD-FORMED STEEL STUD WALL - GWP GAS EMISSIONS

860

104

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

10,000


Superstructure Wall

Slab on Grade

Foundation


WOOD – GWP GAS EMISSIONS

• Sourcing is highly variable• Transportation of forest products• Management of forest

• Complexity of natural carbon cycle

• Include footprint of construction waste?

• Value of wood’s sequestration of carbon in a long-lived and durable building?

http://owic.oregonstate.edu


SUSTAINABLE FORESTRY CARBON

CYCLE

www.realoutdoorliving.org


WOOD STUD WALLGWP GAS EMISSIONS

227

96

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

10,000


Superstructure Wall

Slab on Grade

Foundation


INSULATED CONCRETE FORMS

• Inherent air barrier system / no convection currents

• Concrete has high thermal mass

• Block, Panel, & Plank systems

• Over 20 brands in North America

• Can be used for

• Residential and Non-residential

• Basement and above grade walls



• Structurally – reinforced concrete walls and beams

•Connections penetrate inner insulation layer

• Remove inner insulation at slabs at retaining walls

• Inspection during concrete placement is critical

•Can use high volume fly ash concrete





Boys and Girls Club of Binghamton

Completed 2009


INSULATED CONCRETE FORMSGWP GAS EMISSIONS

1023

850

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

10,000


Superstructure Wall

Slab on Grade

Foundation


INSULATED CONCRETE FORMS:MARKET PENETRATION

• Current

• Residential US Market - About 8%

• Commercial US Market - Less than 1%

• Potential

• Residential, low-rise multifamily, institutional, religious, commercial

• Potential high appeal with very low CO2e concrete mixes *

* - if CO2e is ever given market value


STRUCTURAL INSULATED PANELS


STRUCTURAL INSULATED PANELS:STRUCTURAL ASPECTS

• Prefabricated insulated structural elements for roofs, walls, even floors

• AKA foam-core panels, stress-skin panels, sandwich panels

• Walls can take vertical loads, in-plane and perpendicular lateral loads

• Walls can have steel or wood reinforcing

• Roofs and floors can span several feet, depending on thickness


STRUCTURAL INSULATED PANELS:GWP ASPECTS

• Excellent thermal properties:

• 4" SIP wall beats the R-value of a 6" stud wall with batt insulation

• Continuous insulation - No insulation gaps or bunching

• Air barrier if joints are taped. No convection currents

• OSB requires no large timbers

• No studs to create thermal breaks

• GWP highly dependent on insulation!


GWP OF INSULATION

TYPES

Source:

Environmental

Building News


POLYISO STRUCTURAL INSULATED PANEL

GWP GAS EMISSIONS

364

89

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

10,000


Superstructure Wall

Slab on Grade

Foundation


EPS STRUCTURAL INSULATED PANEL

GWP GAS EMISSIONS

227

96

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

10,000


Superstructure Wall

Slab on Grade

Foundation


XPS STRUCTURAL INSULATED PANEL

GWP GAS EMISSIONS

7516

96

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

10,000


Superstructure Wall

Slab on Grade

Foundation


STRAW BALE CONSTRUCTION:STRUCTURAL ASPECTS

• Can take vertical and lateral loads, due to reinforced stucco

• Structurally, two types:

• Load bearing - “Nebraska” style

• Wood post and beam infill

• Watch the details, especially:

• Bases – wood “toe ups”

• Tops – box beams

• Plumbness of walls is critical

www.solarhaven.org


STRAW BALE CONSTRUCTION: GWP GAS ASPECTS

• Straw GWP is very small -especially if locally sourced

• Location of building greatly affects footprint

• Erection - can be very low

• Small amounts of steel and wood

• Stucco - usually cement

• Wide concrete footings www.texastinyhomes.com


STRAW BALE CONSTRUCTION:GWP GAS EMISSIONS

486

69

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

10,000


Superstructure Wall

Slab on Grade

Foundation


CROSS-LAMINATED TIMBER:STRUCTURAL ASPECTS

• Structurally, most similar to precast concrete bearing walls and slabs

• Design methodologies are being developed

• Fire protection issues should not be show-stoppers

• Can go 10 + stories

• Hybrid systems – lower levels of concrete or steel


CROSS-LAMINATED TIMBER:GWP GAS ASPECTS

• Additional insulation needed, but thermal mass and properties of wood are beneficial

• Currently more common in Europe and Australia than U.S.

• CO2-e highly dependent on sourcing – location & forest management

• Other wood-based structural systems exist, including Woodcube, Massivtre


CROSS-LAMINATED TIMBERGWP GAS EMISSIONS

1058

81

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

10,000


Superstructure Wall

Slab on Grade

Foundation


GWP GAS EMISSIONS -SUMMARY

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

CO2e/100sf

Construction of Walls Only


RECOMMENDATIONS

• “Dematerialize” your project

• Eliminate use of Extruded Polystyrene and

Closed-Cell non water-based Spray Foam (until blowing agents are replaced)

• Consider CO2-e assessment of construction projects (part of “integrative design”?)

• Include sitework in CO2-e assessment (especially asphalt and concrete)

• Consider alternative systems (e.g. SIPs, ICFs, timber or cross-laminated timber, straw bale)


RECOMMENDATIONS

• Concrete

• Do not over-specify concrete strength

• Use SCM as much as possible

• Minimize foundation concrete area

• Masonry

• Specify CMU’s with SCM and minimize Portland cement

• Specify SCM in grout

• Consider alternative low-cement masonry units

• Steel

• Consider salvaged or reuse of steel

• Specify steel produced in Electric Arc Furnaces, not BOF’s

• Wood – Consider its use where codes allow


A NON-TECHNICAL PROBLEM

The market value of determining

the GWP of a construction project

is currently LESS than ZERO.


QUIZ

• What’s a typical CO2e emissions figure for a yard of concrete?

• What two types of insulation have very high CO2e?

• Name one strategy to reduce CO2e from masonry construction.

• Name three things that influence heating energy usage in a building.

• How much CO2e does erected structural steel emit into the atmosphere, per ton?


THANK YOU FOR LISTENING!Questions? Comments? Discussion?

Klepper, Hahn & Hyatt Structural Engineering

315.446.9201 Landscape [email protected] Building Envelope Systems

Jim D’Aloisio, P.E., SECB, LEED AP BD+C

Documents

Alternative structural systems - The C&S Companies · CNY Engineering Expo 3 Nov 2014. ... Finally, some alternative structural systems have significant benefits, including the potential