energyand the environment - softwood lumber5 energy and the environment in residential construction...

I N R E S I D E N T I A L C O N S T R U C T I O N

Energyand the

Environment

Sustainable Building Series No. 1

The operating energy use in buildingsrepresents a major contributor to fossilfuel use for space heating and cooling,lighting and the operation of appliances.Fossil fuels release greenhouse gases suchas carbon dioxide and nitrous oxide. Forthis reason, the need to save energy byreducing operating energy consumptionin buildings is widely recognized through-out the world.

Less attention has been given to theneed to reduce the embodied energy ofstructures because the amount of embodiedenergy is small in comparison to theamount of operating energy over a building’slife cycle. Nevertheless embodied energyresults in considerable emissions of water

Introduction

pollutants to our rivers and oceans andemissions of air pollutants contributingto air pollution and greenhouse gasemissions.

In the 1990’s, the Canadian WoodCouncil launched "Wood the RenewableResource", a series of publications forarchitects, engineers, cost consultantsand clients, examining how buildingproducts affect the environment throughtheir life cycle. Building upon this start,this publication provides new life-cycleassessment (LCA) data and offers anupdated comparison study by presentingdata for both the embodied energy andoperating energy of three 2,400 sq. ft.single-family homes.

There are complex issues surroundingthe concept of sustainability. Immediateactions to address the environmentalimpacts of buildings and constructionfocus on the reduction of constructionwaste and the reduction of energy con-sumption in buildings.

The oil embargoes of the 1970s resulted in energy conservation guidelines and

codes. National policies respond to climate change concerns and sustainability

issues that arise from the burning of fossil fuels, air pollution and concerns

surrounding global warming.

3Energy and the Environment

in Residential Construction

To date, there is not one single defini-tion of sustainable buildings or sustainableconstruction that is accepted worldwideand the most frequently quoted definitionof sustainable development is that of theUnited Nations World Commission onEnvironment and Development (1987):"The ability of humanity to ensure thatdevelopment meets the needs of thepresent without compromising theability of future generations to meettheir own needs."

While sustainable building guidelinesand building rating systems aim to reducethe environmental impacts of buildings,none assess the total impact of a buildingon the environment.

Decision makers need reliable data forthe development of policies and performance-based standards that will become thebenchmark of environmental values. Withscientific measurements, such as life cycleassessment, one can move from prescrip-tive-based thinking to performance-basedcriteria. By creating performance-basedcriteria, we can create a sensible road tosustainability.

OPERATING AND

EMBODIED ENERGY

According to the International EnergyAgency, comprised of 22 countries thatinclude both the United States and Canada,on average, one-third of operating energyusage in the developed world goes for heat-ing, cooling, lighting and the operation ofappliances in non-industrial buildings suchas homes, offices, hospitals and schools.These estimates do not take into accountthe amount of embodied energy in buildingproducts and its impacts on the environment.

Operating energy efficiency in resi-dential and commercial buildings is greatlyenhanced in highly insulated and airtightbuilding envelope systems, high perform-ance windows, high-energy efficiency heat-ing, cooling and water heating equipment,low energy lighting and energy efficienthome appliances.

Increased insulation in foundations,walls and attics, and insulated doors andwindows reduces the operating energy inbuildings. However the need for insulat-ing products contributes to higherembodied effects.

Wood is a good and natural insulator.Due to its cellular structure, wood traps airresulting in low conductivity and good insu-lating properties. Steel conducts heat 400times faster than wood. High conductivity

SUSTAINABILITY

The relationship between the principles of sustainable development and the

construction sector includes similar challenges: environmental quality, energy

conservation, resource efficiency and human health.

causes thermal bridging leading to increasedenergy use for heating and cooling. Becausesteel and concrete must overcome lower R-values due to thermal bridging, there is aneed for additional insulation.

Understanding the need to reduceoperating energy in buildings and theimportance of the embodied energy ofstructures leads to a more rigorousapproach to sustainability. While it is easi-er to focus solely on the conservation ofoperating energy, the effects of embodiedenergy in structures, such as global warm-ing potential, solid wastes, air and waterpollution, are significant. Of the majorbuilding materials, wood requires the leastenergy to produce.

The initial embodied energy in build-ings represents the energy consumed in theacquisition of raw materials, their process-ing, manufacturing, transportation to thesite, and construction. The initial embodiedenergy has two components. The directenergy, that is the energy used to manufac-ture and transport building products to thesite and to construct the building. The indi-rect energy is the energy use associated withprocessing, transporting, converting anddelivering fuel and energy to its point of use.

The recurring embodied energy inbuildings represents the non-renewableenergy consumed to maintain, repair,restore, refurbish or replace materials, com-ponents or systems during the life of thebuilding.

As buildings become more energy-efficient the ratio of embodied energy tolifetime operating energy consumptionbecomes more significant.

Sustainable Buildings

LCA includes the entire life cycle of aproduct, process, or activity, from extract-ing and processing raw materials to man-ufacturing, transportation and distribu-tion, use, maintenance, recycling and finaldisposition.

It includes environmental impactssuch as acid rain, air pollution, ecologicaltoxicity, fossil fuel depletion, global warm-ing, habitat alteration, human health,indoor air quality, ozone depletion, smog,and water intake (current cradle to gravesystem). Based on LCA, wood productshave proven to be one of the most environ-mentally responsible building products.

In the concept of cradle to cradle,where materials are designed to be returnedsafely to the soil or to flow back to industryto be used again, wood is a material that canbe recycled or reused and ultimately isbiodegradable. With good forest manage-ment practices, wood is the most environ-mentally responsible building material.

available LCI data for commonly used prod-ucts and processes. Generally, access to LCIdatabases are restricted or protected bycopyright agreements. The LCI Project onthe other hand will make the informationavailable to all and will provide an openexchange of information.

The LCI Project was conceived by theATHENATM Sustainable Materials Instituteas a three-phase effort: Phase I was anintensive initiation and planning phase andwas undertaken by the Institute in associa-tion with Franklin Associates Ltd. andSylvatica, with funding through theNational Renewable Energy Laboratory(NREL) from the US Department of Energy,the General Services Administration, andthe US Naval Facilities EngineeringCommand. The U.S. LCI Database Project –Phase I Final Report was completed inJanuary 2002 and is available online on theNREL website.

The Institute is now undertakingPhase II, which involves basic data col-lection, analysis and review as well asthe development of data formats and aUser’s Guide.

Following is a comparative environ-mental impact LCA assessment of embodiedand operating energy of steel, concrete,and wood residential construction. Theimpact assessment includes primaryenergy, global warming potential, air pollution, water pollution, resource use,and solid waste.

For more information please visit the ATHENATM SustainableMaterials Institute at http://www.athenaSMI.ca and theNational Renewable Energy Laboratory athttp://www.nrel.gov/lci.

LIFE-CYCLE ASSESSMENT (LCA)

Life-cycle assessment (LCA) is the recognized international approach to assess

the environmental merits of products or processes as set out in the ISO 14000

series of standards.

The not-for-profit ATHENATM

Sustainable Materials Institute (theInstitute), a world-leading source of life-cycle assessment data and tools, is findinganswers to critical questions about the envi-ronmental impact of buildings and buildingproducts. The Institute’s work has gainedrecognition from environmental authoritiesin Canada, in the United States and abroad.

Life-cycle inventory (LCI) is a corner-stone of any life-cycle assessment because itinvolves tracking and recording basic flowsfrom and to nature (resources and wastes)for specific products or processes. All sub-sequent LCA calculations or steps arederived from or reflect basic LCI data. Thelack of widely available LCI is recognized asthe main reason LCA data is viewed asexpensive and time consuming.

The U.S. LCI Database Project (LCIProject) is a public/private research part-nership to develop and make publicly



integrated into the software. In the origi-nal 1999 study, the effective R-value of thewall envelope systems was different for thethree designs and the effects of varying R-values were not included in the results.

Operating energy differences betweenthe designs are now explicitly consideredin this study. And lastly, in the earlierstudy all the common elements (e.g.,cladding, windows, roofing, etc.) sharedamong the three designs were excludedfrom the analysis to underscore the differ-ences across the three design scenarios.However, in this present study these com-mon elements are included in the analysisas they have a direct bearing on operatingenergy use calculations and modeling.

Concrete Design

Steel Design

Wood Design

This updated study addresses all theaforementioned factors, providing a morethorough environmental assessment of thethree alternative material designs (struc-ture and envelope) for a 2,400 sq. ft. single-family home built in the Toronto marketover the first 20 years of its lifespan, theaverage lifespan being 70 years.

While the three homes are similar inoutward appearance, square footage anddivided living area, they are markedly dif-ferent in terms of the structural materialsused to achieve the final design. One isdesigned using softwood lumber and engi-neered wood I-joist framing, the seconddesign incorporates light frame steel for itsstructure,and the third design uses insulatedconcrete forms (ICF) and a composite concrete slab on steel joist (HAMBROTM)floor system.

Because sheet metal and concreteroof-framing methods are not readily avail-able or in common use, the decision wasmade to use wood trusses for all threedesigns to reflect current building practices.

The assessment results are summa-rized into six key measures covering totalprimary energy (operating and embodiedenergy, where embodied energy includesthe direct and indirect energy associatedwith extraction, manufacturing, on-siteconstruction and maintenance and repairactivities during the first 20 years of operat-ing these homes, including all transporta-tion energy within and between these activ-ity stages), weighted raw material use,greenhouse gas potential, measures of airand water pollution, and solid waste emis-sions. See Figure 1.

OBJECTIVES OF ASSESSMENT

The Canadian Wood Council (CWC) commissioned the ATHENATM Sustainable

Materials Institute (the Institute) to update and expand on an earlier 1999 CWC

study completed by the Institute which contrasted the initial environmental impact

of wood, steel and concrete single family home designs.

Nor

mal

ized

to W

ood

Valu

e =

1

Comparative EnvironmentalImpact Assessment Prepared for the Canadian Wood Council by

the ATHENATM Sustainable Materials Institute

At the time of the first study, theInstitute’s Environmental Impact Estimator(EIE) software could only simulate theenvironmental implications of structuralsystems and hence, all the building enve-lope components were assessed throughcalculations using life cycle inventory(LCI) data that had not been entered inthe software.

Since that original study, all theInstitute’s life cycle databases have beenupdated and expanded to include envelopematerials, and other systems have beenadded. The original study included a verypreliminary quantity take-off for insulatedconcrete forms (ICF) – a key assembly inthe concrete design. ICFs are now fully

Solid W

aste

Resource Use

Energy

Water Pollu

tionGW

PAir Pollu

tion

Figure 1: Embodied Effects Relative to the Wood Design across all Measures

Energy and the Envrironment in Residential Construction

6

LCA METHODOLOGY

A full life cycle assessment (LCA) is a formal process of examining the environ-

mental impacts of a material, product or service through its entire life cycle, from

raw resource or material acquisition through manufacture and use to waste dis-

posal. Instead of a single-attribute analysis of a material’s environmental impact,

such as its recycled content, LCA takes a "holistic" approach to the possible

impacts of material choices throughout their respective life cycle.

assemblies, as well as a full range ofenvelope components (e.g., cladding,roofing, insulation, glazing. etc.). It covers abuilding’s life cycle stages from the "cradle"(natural resource extraction) through to its"end-of-life" (grave). Specifically the modelencompasses the following building lifecycle stages:

Product manufacturing: includesresource extraction, resource transportationand manufacturing of specific materials,products or building components.

On-site construction: includes prod-uct/component transportation from thepoint of manufacture to the building siteand on-site construction activities.

Maintenance and replacement:includes life cycle maintenance and replace-ment activities associated with the struc-ture and envelope components based onbuilding type, location and a user defined"design life" for the building.

Building "end-of-life": simulates dem-olition energy and final disposition of thematerials incorporated in a building at theend of the building’s life.

The software converts operating ener-gy to primary energy and emissions toallow users to compare embodied and oper-ating energy environmental impacts overthe building’s life. The operating energycalculator requires a separate estimate ofoperating energy as an input to themodel. HOT2000 annual fuel consumption

simulation results by fuel type for each ofthe design scenarios were entered in the EIEsoftware. The software then estimated theregionally applicable emissions to air, waterand land associated with the type andquantity of fuels used for each of the threehouse designs over a 20 year period.

HOT2000 is an operating energyanalysis program for residential buildingsdeveloped by Natural Resources Canadaand freely distributed via the web(www.buildingsgroup.nrcan.gc.ca).

It is a versatile whole house operatingenergy simulator and is used to evaluatenew housing designs for the R-2000 pro-gram on a regional basis.

R-2000 is a program offered by NaturalResources Canada’s Office of EnergyEfficiency that encourages and certifies thebuilding of energy efficient houses that areenvironmentally responsible and healthy tolive in, according to certain criteria.(Another program sponsored by theGovernment of Canada is the Super E® HouseProgram for countries other than Canada,supported by Canadian technology, expertiseand training.)

The HOT2000 software program hasbeen in use for over 15 years acrossCanada and around the world. Version9.01 of the program was used in this proj-ect. Morrison Hershfield completed theHOT2000 simulations for the three alter-native material designs.

The life cycle inventory (LCI) is fund-amental to an LCA. As the name implies,the LCI involves collecting and documentingdata on the relevant environmental flowsor burdens associated with the various lifecycle stages, including transportationwithin and between stages and theupstream effects of energy use (i.e., theenergy and emissions associated with pro-ducing and moving energy). Once the LCIis in place, the potential environmentalimpacts of a material, product or system(e.g. a house) can be characterized in termsof several internationally recognizedmeasures of environmental loading, suchas the following:- acidification- global warming- smog formation- solid waste.

While LCI/LCA has been around invarious forms since the early 1960s, it wasonly in the mid-to-late 90s’ that the protocolfor completing such studies was standard-ized by the International Organization forStandardization (ISO14040-42). TheInstitute subscribes to this internationalprotocol and over the years has adjusted itsown methodology to be in step with the ISOprotocols governing the application of LCA.

Currently, the Athena™ EnvironmentalImpact Estimator (EIE) software (v3.0)encompasses LCI profiles for steel, woodand concrete structural products and



In terms of results, the EIE softwareprovides a detailed environmental lifecycle inventory of the embodied effectsassociated with the building as well as a setof six summary measures. These summa-ry measures include total primary(embodied and operating) energy and rawmaterial use; greenhouse gas potential(both fuel and process related); measuresof air and water pollution; and solid wasteemissions.

BUILDING DESIGN AND ENERGY SIMULATION CONSIDERATIONS

CWC’s design team [Peter Gabor (Architect) and Raymond van Groll (Structural

Engineer)] provided the Institute with structural and elevation drawings, Figures 2

and 3, and envelope details for each of the three designs.

The software and its embedded data-bases are North American in scope, repre-senting average or typical manufacturingtechnologies and appropriate modes anddistances for transportation. The modelsimulates 12 geographic regions represent-ed by Vancouver, Calgary, Winnipeg,Toronto, Ottawa, Montreal, Quebec City,Halifax, Minneapolis, Atlanta, Pittsburghand a US Average. This study drew on thesoftware’s Toronto regional database.

With the drawings and envelopedetails in hand, the Institute retained theservices of Morrison Hershfield’s BuildingsGroup to review the drawings and materiallists for accuracy, gauge the comparative"fairness" of the alternative designs andassist in entering assembly and materialdata into the ATHENA™ EIE model.

Morrison Hershfield also completedthe operating energy simulation for thethree material designs.

The focus of the energy simulationswas to determine the influence of the varying

wall envelopes on operating energy,specifically, space heating and cooling. Tothis end, the simulations assumed a high-efficiency natural gas-fired, forced-air furnace and a 3-ton conventional air conditioner for all three material designsassuming Toronto climatic conditions.Plug-loads and domestic hot water heatingwere deemed to be the same for all threematerial designs and were excluded fromthe assessment.

Figure 3

A Master BedroomB Family RoomC DinetteD KitchenE HallF GarageG Entry

H Living/DiningI Attic

J Open to BelowK BedroomL Upper Hall M Den

Figure 2

53’-8

“

38’-8“

K B

F

E

C

D

H

G

I J

LA

M

K


8

• exterior above grade walls finished in5/8" gypsum to provide racking strength;

• interior steel stud spacing 2’ o/c for non-loading partition walls and perimeter oflivable basement area;

• rigid insulation on above grade walls(extruded polystyrene (XPS));

• no building paper required behind brickcladding.

Hybrid Concrete design assumptions

• foundation footing width as per OntarioBuilding Code for above grade concretestructures;

• exterior above grade ICF walls finished in5/8" gypsum;

• 10M rebar 3’ long reinforcement aroundwindow openings in ICF wall system;

• 10-2’ stirrups at each stirruped opening;

• ICF constructed using expanded poly-

styrene (EPS) and polypropylene form ties.

• all three roof framing designs use woodtrusses;

• roof framing: combination of roof raftersand light frame wood trusses, insulation(R31 fiberglass batt) and asphalt shingles;

• strip footings under foundation wallsmodeled as 8" thick and square footingsunder column locations as 12" thick.

Wood design assumptions

• basement exterior wall vapour barrierincluded with use of fiberglass batt insu-lation;

• spacing of studs at 2’ o/c for non-loadbearing interior partition walls andperimeter of livable basement area;

• i-joist web 3/8" OSB and flange 2.5"x1.5"lumber.

Steel design assumptions

• basement exterior wall vapour barrierincluded with use of fiberglass batt insu-lation;

The assumptions and substitutions aredescribed below in terms of global variablesas well as specifics concerning each materi-al design scenario. Otherwise all designinputs were as per specified in the drawings(see cross-section component detail draw-ings for specifics, Figures 4, 5 and 6).

Global assumptions across allthree material designs

• clay brick exterior cladding finish;• all windows operable double glazed units

with PVC frames, low "E" tin, and Argonfilled;

• interior finish limited to painted gypsumboard finishes on ceilings and walls;

• anything exterior to the building (e.g.,landscaping, sidewalks, driveways, etc.)excluded from the assessment;

• all interior finishes (e.g. floor coverings,doors and wall finishes) excluded;

• optional basement bath and laundryroom excluded, but fourth second floorbedroom and bath included in all threematerial design scenarios;

ASSUMPTIONS

The ATHENA™ model is a conceptual design tool and in working

with final engineering designs requires a number of assumptions

to permit modeling of these detailed designs. This section briefly

describes assumptions and substitutions made during the

course of the analysis. Figure 4: Wood House Cross-section

Roof• No. 210 asphalt shingles• No. 15 building paper• 1/2-in. OSB sheathing• Metal plate-connected wood

trusses @ 24 in. o/c• R31 batt insulation • 6 mil polyethylene vapour barrier • 1/2-in. gypsum board

Partition Walls• 1/2-in. gypsum board (both sides) • 2 x 4 wood studs @ 24 in. o/c

Floors• 5/8-in. OSB sheathing • 9-1/2 in. wood I-joists at 16 in.

o/c with 2 x 2 cross-bridging • 1/2-in. gypsum board

Exterior Wall• 4 in. brick veneer• 1 in. air space • No. 15 building paper• 3/8-in. OSB sheathing • 2 x 6 wood studs @ 16 in. o/c• R19 batt insulation • 6 mil polyethylene vapour barrier • 1/2-in. gypsum board

Foundation Wall• Damproofing• 8 in. concrete wall • 2 x 4 wood studs @ 24 in. o/c,

installed 2 in. out from wall • R19 batt insulation • 6 mil polyethylene vapour barrier



Both the wood and steel design effec-tive R-values were developed using the par-allel path approach as outlined and devel-oped in the National Model Energy Code forHouses. Currently ICFs are not covered inthe Energy Code and thus it was necessaryto develop an effective R-value estimate forthis system separately.

Because there is an ever-expandingarray of ICF systems and constructiondetails for these systems, there is also a widevariation in their effective R-values. A 2002field study research report by Oak RidgeNational Laboratory indicates an effectiveR-value for the ICF residential structuretested at R-16. We believe this to be at the

Figure 5 – Sheet Metal House Cross-section

Roof• See Wood House (Figure 4)

Partition Walls• 1/2-in. gypsum board (both sides)• 3-5/8 in. x 0.018 in. steel studs @ 24 in. o/c

Floors• 5/8-in. OSB sheathing • 8 in. x 0.048 in. steel joists @ 16 in. o/c

1.5 in. x 0.048 in. strap cross-bridging• 1/2-in. gypsum board

Exterior Wall• 4 in. brick veneer• 1 in. air space • 1-1/2 in. (R 7.5) rigid insulation • 3-5/8 in. x 0.036 in. steel studs @ 16 in. o/c• R12 batt insulation • 6 mil polyethylene vapour barier • 5/8-in. gypsum board

Foundation Wall• Damproofing• 8 in. concrete wall • 3-5/8 in. x 0.018 in. steel studs @ 24 in.

o/c installed 2 in. out from wall • R19 batt insulation • 6 mil polyethylene vapour barrier

Roof• See Wood House (Figure 4)

Partition Walls• 1/2-in. gypsum board (both sides)• 2 x 4 wood studs @ 24 in. o/c

Floors• Hambro floor (composite concrete/steel-joist floor)• 1/2-in. gypsum board

Exterior Wall• 4 in. brick veneer • 1 in. air space • ICF (insulated concrete form) R20

expanded polystyrene formwork• 6-1/4 in. concrete wall • 5/8-in. gypsum board

Foundation Wall• ICF (insulated concrete form) R20

expanded polystyrene formwork• 6-1/4 in. concrete wall supported on 24 in. wide

concrete footing

construction (e.g., around windows and atmain assembly intersections). Here againwe ran into a scarcity of verified air infiltra-tion results for ICF construction and weassumed the air infiltration rate to be thesame across all three systems.

Table 2 summarizes the HOT2000 fuelconsumption simulation results for each ofthe three framing methods on a per annumbasis. The values reported include all relat-ed natural gas and electricity use associatedwith space heating and cooling. Excludedfrom the results is electricity usage associ-ated with plug loads and natural gas used tofire a domestic hot water heater, both ofwhich were the same for all house designs.

The fuel consumption results indicatethat, relative to the wood house envelope,the steel design would consume about 7%more natural gas during the heating season,but it would use 1% less electricity duringthe air conditioning season. Essentially thehigher thermal resistance of the wood enve-lope design works against itself during thecooling season.

Figure 6 – Concrete House Cross-section

RESULTS

Hot 2000 Simulation Results

While all three house-designs met energy code requirements, their respective

effective R-values were not equivalent. Table 1 sets out the insulation material

R-values and the estimated average effective R-values for the exterior walls for

each of the three home designs.

low end of the R-value spectrum for thesesystems and in fact, expect some systems toattain their stated material rating. However,with the paucity of verified results for any ofthe ICF systems we have set the effective R-value of the ICF equal to that of the woodenvelope, which is in the upper half of therange for ICF systems.

Another energy simulation issue thatwe wrestled with was air infiltration differ-ences between the three systems. Whilewood and steel framing would typicallyhave a similar air infiltration rate, the ICFsystem would tend to have a lower air leak-age rate than either the wood or steel fram-ing systems, depending on the quality of


10

This phenomenon doesn’t hold truefor the ICF design due to the temperaturemoderation effect of the ICF design’s greaterthermal mass (primarily due to itsHAMBROTM floor system). So while thewood envelope design has a 1% natural gasuse advantage during the heating season, itsair conditioning electricity disadvantage isin the order of 7% due to the ICF’s thermalmass advantage. The natural gas and elec-tricity values as presented in Table 2 wereentered into the ATHENATM EIE software tocalculate the total primary energy and relat-ed emissions to air, water and land associat-ed with the use of the fuels over 20 years. 1

ATHENATM EIE Results

Table 3 summarizes the environmentaleffects embodied in the structure and enve-lope of the three house designs as well astheir respective 20-year space heating andcooling effects.

Foundations include all reinforcedconcrete strip and column footings as wellas the basement and garage slab-on-gradefloors. The wall grouping includes all belowand above grade walls as well as partition

walls. The floors and roof assembly groupincludes the first and second story floors aswell as the roof. The column and beamsassembly group includes all built-up orheavy beams and jackposts.

Embodied Effects Summary2

(for its first 20 years)

Relative to the wood design, the steeland concrete designs• embody 26% and 57% more energy;• emit 34% and 81% more greenhouse

gases;• release 24% and 47% more air pollution;• discharge 4 and 3.5 times more water

pollution;• use 11% and 81% more resources from a

weighted resource use perspective; and• produce 8% and 23% more solid wastes,

respectively.

Using embodied energy as an indica-tor, the majority of the difference betweenthe three designs can be traced to theirrespective wall and floor structural framingand insulation material type differences.

Operating Energy EffectsSummary

Despite the variation in the amounts ofnatural gas and electricity reported in Table 2,the net difference in primary energy use isless significant than one might suspect.

Relative to the wood design and over a20-year period, the steel design• consumes 5% more primary energy;• emits 5% more greenhouse gases;• emits 6% more air pollution and the

same amount of water pollution;• uses 1% more resources from a weighted

resource use perspective; and• produces 3% more solid wastes.

Table 2 – Annual Fuel Consumption by Mode and Material Design

Wood Design 1734 1456 1795

Steel Design 1852 1469 1776

Concrete Design 1753 1458 1669

Natural Gas m3 Electricity kWh Electricity kWhspace heating space heating air conditioning

1 As a sensitivity test we also ran the ICF design withan effective R-value of twenty. The difference betweenthe R-18 and R-20 effective R-value ICF designs inelectricity and natural gas usage was 0.2% and 4%, respectively.

2 Result differences of less than 15% should be consideredequal. While more work will be required to set useful tolerance limits when comparing two or more designs,relative differences greater than 15% are generally considered significant.

Table 1 – Insulation and Whole Effective R-Values by Material Design

Units Wood Design Steel Design Concrete Design

Note: Whole wall effective R-values are for the complete exterior wall system

Wall Insulation R-Value only BTU/ft2hr 19.0 19.5 20.0

Whole Wall Effective R-Value BTU/ft2hr 18.1 15.0 18.1



Relative to the wood design and over a 20-year period, the concrete design• consumes 1% less primary energy;• emits the same amount of greenhouse

gases;

• the other four measures were also foundto be either the same or tending to the negative side.

The similarity of the above operatingenergy results is in part a function of the

various fuels used to generate electricity inOntario, their conversion efficiency intoelectricity, and cleanliness relative to thenatural gas heating fuel.

Table 3: 20-Year Environmental Results Summary (Embodied and Operating Effects)

Design by Assembly Primary Global Warming Air Pollution Water Pollution Weighted Resource Solid WastesComponents Energy Potential Critical Volume Critical Volume Use (kg)

(Gj) (Eq.CO2 kg) Measure Measure (kg)

Wood Design

Foundations 73 6474 857 3 64395 2811Walls 687 36528 9474 3 142752 9848Floors and Roof 287 9346 3132 8 36844 4006Column & Beams 73 3164 411 15 7033 469Total Embodied 1121 55512 13874 29 251024 17134Total 20 yr Operating Energy 2192 102680 44919 3 146666 7184

Grand Total 3313 158192 58793 32 397690 24318

Steel Design

Foundations 73 6474 857 3 64395 2 811Walls 894 48160 12044 41 159407 10786Floors and Roof 385 16332 3975 57 47196 4 420Column & Beams 64 3265 389 18 6533 469Total Embodied 1417 74231 17265 119 277531 18 486Total 20 yr Operating Energy 2296 108020 47486 3 148387 7 396

Grand Total 3713 182251 64751 122 425918 25882

Concrete Design

Foundations 60 5045 658 3 48198 2311Walls 1065 65110 14248 2 304089 12247Floors and Roof 542 26091 4934 78 93367 5871Column & Beams 92 4167 516 19 9389 642Total Embodied 1758 100413 20356 102 455043 21071Total 20 yr Operating Energy 2184 102648 45067 3 142471 7069

Grand Total 3942 203061 65423 105 597514 28140

Totals may not add exactly due to rounding.


12

Figure 7: Global Warming Potential

Total Embodied Total 20 yr Operating Energy

CO2

Equi

vale

nt (k

g)Cr

itica

l Vol

ume

Mea

sure

Figure 9: Water Pollution

Summing the total embodied andoperating energy for twenty years for eachdesign and then comparing these overallresults relative to the wood design, indicatesthat both the steel and concrete designs• embody and consume 12% and 20%

more energy;• emit 15% and 29% more greenhouse

gases;• release 10% and 12% more air pollution;• discharge 3 and 2.25 times more water

pollution;• use 7% and 50% more resources from a

weighted resource use perspective; and• produce 6% and 16% more solid wastes,

respectively.The fundamentals of large numbers

and percentage comparisons tend to indi-cate smaller differences. But another way oflooking at these results would be to com-pare them on the basis of years of operatingenergy and related greenhouse gas releasessaved by building the wood design (thelower embodied design) instead of either ofthe other two alternative designs.

The savings attributable to buildingthe wood home over the steel and concretehomes is equivalent to about 2.5 years ofoperating energy and 3.6 years of globalwarming gas emissions in the case of thesteel design and 5.5 years of operating ener-gy and 8.6 years of global warming gasemissions in the case of the concrete design.

Summary

Figure 8: Air Pollution

Wood Design Steel Design Concrete Design





Criti

cal V

olum

e M

easu

re



In terms of environmental impacts,Figures 7 and 8 represent the total embod-ied and total 20-year operating energy ofthe wood, steel and concrete designs interms of global warming potential and airpollution, respectively.

Figure 9 verifies the impact on waterpollution where the water toxicity level ofboth the steel and concrete is considerablymore significant than wood.

Figures 10 and 11 present the weightedresource use and solid waste.

Figure 12 illustrates the primaryenergy for all three designs, both the totalembodied energy and the total 20-yearoperating energy.

(kg)

(kg)

Prim

ary

Ener

gy (G

J)

Figure 12: Primary Energy







Figure 11: Solid Waste

Figure 10: Weighted Resource Use

To create a sustainable world a holisticapproach to sustainability is needed.

Conclusion

Adopted by many countries, wood-frame construction is the residentialbuilding system of choice. It is strong andmeets the challenges of high-wind andearthquakes. Easy to connect and insu-late, wood is the only major buildingmaterial that is renewable.

Wood is a high-quality material.Engineered wood products are found inhouses, commercial and industrialbuildings and offer tolerances in stability,

consistency, and straightness. From themanufacturing of complete homes infactories, to the shipping of wall andfloor assemblies at home and abroad, tothe prefabrication of wall units on site,the modularization of wood-frame construction delivers cost savings andquality for builders.

In conclusion, where wood comesfrom well-managed forests, it is the envi-ronmental building material of choice.

Cover and page 2 bottom:

Jones Farmstead, Salmela Architect.Photos by Peter Bastinelli Kerze.Citation Award, 2002 Wood Design Awards;www.wooddesignawards.com.

Page 2 top and page 14 bottom:

Maison Goulet, Saia Barbarese Topouzanov architects. Photo by Marc Cramer. Honour Award, 2003 Wood Design Awards;www.wooddesignawards.com.

Page 7:

Photo by Roy Grogan.

This page top:

Caretaker’s Complex, Gray Organschi Architecture. Photo by Paul Warchol. Merit Award,2001 Wood Design Awards;www.wooddesignawards.com.



Institute Reports

Demolition Energy Analysis ofOffice Building StructuralSystems. Mar./97 Prepared by M. Gordon Engineering.

The Ecological Effects ofResource Extraction inOntario. Mar./97 Prepared byWayne B. Trusty and Associates& Dr. R. Paehlke, EnvironmentalPolicy Research.

Ecological Carrying CapacityEffects of Building MaterialsExtraction. Sept./93 Preparedby Dr. R. Paehlke, EnvironmentalPolicy Research (includes separately bound annotatedbibliography).

Assessing the RelativeEcological Carrying CapacityImpacts of ResourceExtraction. Aug./94 Preparedby Wayne B. Trusty andAssociates & Dr. R. Paehlke,Environmental Policy Research.

A Life Cycle Inventory ofSelected Commercial RoofingProducts. Apr./01 Prepared by Franklin Associates, a Serviceof McLaren-Hart/Jones.

A Life Cycle Inventory forRoad and Roofing Asphalt.Mar./01 Prepared by FranklinAssociates, a Service ofMcLaren-Hart/Jones.

Life Cycle Analysis of AsphaltImpregnated Fiberglass Built-Up Roofing Felts.Mar./01 Prepared by George J.Venta, Venta, Glaser &Associates.

Life Cycle Inventory of ICIRoofing Systems: OnsiteConstruction Effects. Mar./01Prepared by Morrison HershfieldLimited.

Life Cycle Analysis ofResidential Roofing Products.Mar./00 Prepared by GeorgeVenta, Venta, Glaser & Associatesand Michael Nisbet, JANConsultants.

Life Cycle Inventory Analysesof Building EnvelopeMaterials: Update andExpansion. Jun./99 Preparedby Dr. Gregory A. Norris,Sylvatica.

An Exploratory Life CycleStudy of Selected BuildingEnvelope Materials. Jul./98Prepared by Dr. Gregory A.Norris, Sylvatica.

Life Cycle Analysis of Brickand Mortar Products. Sep./98Prepared by George J. Venta,Venta, Glaser & Associates.

A Life Cycle Analysis of SolidWood and Steel Cladding.Sep./98 Prepared by Jamie K.Meil, ATHENATM SustainableMaterials Institute.

Life Cycle Analysis ofGypsum Wallboard andAssociated FinishingProducts. Mar./97 Preparedby George J. Venta, Venta, Glaserand Associates.

Raw Material Balances,Energy Profiles andEnvironmental Unit FactorEstimates for Mini-Mill SteelMaterials. Aug./94 Preparedby Steltech.

Raw Material Balances,Energy Profiles andEnvironmental Unit FactorEstimates for StructuralWood Products. Mar./93Prepared by Forintek CanadaCorp. Updated Apr./00:Summary Report: A Life CycleAnalysis of Canadian SoftwoodLumber Production. Preparedby Jamie K. Meil, ATHENATM

Sustainable Materials Institute.

Raw Material Balances,Energy Profiles andEnvironmental Unit FactorEstimates for Structural SteelProducts. Aug./93 Prepared byStelco Technical ServicesLimited. Updated Mar./02 byMarkus Engineering Services.

Raw Material Balances,Energy Profiles andEnvironmental Unit FactorEstimates for Cement andStructural Concrete Products.Aug./93 Prepared by CANMET& Radian Canada Inc. UpdatedOct./99: Cement and StructuralConcrete Products: Life CycleInventory Update. Prepared byVenta, Glaser & Associates.

Building Assemblies:Construction Energy &Emissions. Aug./93 Preparedby the Environmental ResearchGroup, School of Architecture,University of British Columbia.Updated Mar./03 by MorrisonHershfield Ltd.

Other

Insulated Concrete FormSpecifications. CCMC #12641-Rand personal correspondencewith Steve Lawrence of AAB manufacturing, Cobourg, ON.

Field Validation of ICFResidential Thermal Mass,Air –Tightness and GroundCoupling: A Whole BuildingDemonstration. 2002. OakRidge National Laboratory. USDepartment of Energy. 61pp.

Resources

NOTE: The mention of proprietary products in this publication does not indicate anendorsement by the publisher.

99 Bank Street, Suite 400, Ottawa, Ontario, Canada K1P 6B9 Tel. (613) 747-5544 Fax (613) 747-6264 www.cwc.ca

A publication of the Canadian Wood Council

energyand the environment - softwood lumber5 energy and the environment in residential construction...

Documents