Carbon Assessment of Timber Frame Wall Types
The content of this report was compiled by John Butler (Sustainable Building Consultancy) and Passive House Magazine
2001000 WT1 WT2 WT3 WT4 WT5a WT5b kg operational carbon embodied carbon 140120100806040200 WT1WT2WT3WT4WT5aWT5b 2/mkgCO2wall
TheWT5bdifferent
contribution of the wall types to whole house embodied carbon ranges from 26 % of all embodied carbon for WT2, and 50%
Wall carbon only: embodied CO2e per m2 of wall
Basis for calculations
The calculations were carried out using The AECB’s PHRibbon tool. This is a plugin to Passivhaus Planning Package (PHPP). It draws information from PHPP to calculate the volumes and masses of materials in the building. Materials not accounted for in PHPP are manually calculated. Areas and volumes taken from PHPP data (which may be simplified in PHPP) are adjusted as necessary to accurately reflect the constructed building though the use of external dimensions allows for an estimation of construction wastage. Operational emissions are derived from regulated and unregulated energy use, as calculated by PHPP.
Carbon emissions data for products or materials is sourced from Environmental Product Declarations (EPDs) wherever possible – these are independently verified calculations of the emissions produced by a product or materials at each of the different life cycle stages. Where EPDs are not available information is taken from the best available source at the time, including the INIES1 or ICE2 databases.
Wall carbon only: embodied CO2e per
Calculations follow the RICS Whole Life Carbon Assessment for the Built Environment3 methodology (compliant with European Standard EN 15978). This details the criteria for measurement of the building, sources of carbon emissions data, and standard assumptions to use when specific data is not available (e.g., for end-of-life scenarios, for calculation of construction and demolition emissions, and product life spans). The standard building life span for assessments under RICS is 60 years – this was adjusted to 50 years for this assessment to allow comparison against RIAI 2030 Climate Challenge4 targets (which follows EU Levels approach to lifespan). It is hoped the buildings will
1 INIES, Environmental and health reference data for building, https://www.inies.fr/ 2abouttheinies-database/ICE,InventoryofCarbon and Energy v3 43http://www.circularecology.com/embodied-energy-and-carbon-footprint-database.html(2019),RICS,Wholelifecarbonassessmentforthebuiltenvironment(2017).https://www.rics.org/uk/upholding-professional-standards/sector-standards/buildingsurveying/whole-life-carbon-assessment-for-the-built-environment/RIAI2030ClimateChallenge,(2021),https://www.riai.ie/discover-architecture/riaipublications/riai-2030-climate-challenge
The embodied carbon of the ICF wall) is between 2.3 and 3.4 times higher than WT1, depending on the proportions of GGBS (lower carbon replacement for Ordinary Portland Cement) and steel reinforcement assumed for the ICF walls.
Summary
This report for the ITFMA describes whole life embodied and operational carbon assessment of a reference house, looking at the impact on emissions of four different timber frame wall types (WTs) and two insulated concrete formwork (ICF) walls (a best and worst case) for comparison. All walls modelled have a U value of 0.18 W/m2K.
The embodied carbon of the ICF wall) is between 2.3 and 3.4 times higher than WT1, depending on the proportions of GGBS (lower carbon replacement for Ordinary Portland Cement) and steel reinforcement assumed for the ICF walls.
externally with either rendered blockwork (WT1 and 3) or particle board render carrier and render system (WT2 and 4).
8007006005004003002001000 WT1WT2WT3WT4WT5aWT5b 2e/mCOkg2GIA Combined Operational and Embodied CO2e (net emissions) Whole building Cradle to Grave, A C (50 year lifespan) operational carbon embodied carbon 14012010080602/mkgCO2wall
m2 of wall
Results are reported for the reference building as total tonnes and kg CO2e per square metre of floor area (gross internal areas – GIA), and separately per square metre of wall surface area, over a reference 50year lifespan.
The contribution of the wall types to whole house embodied carbon emissions ranges from 26 % of all embodied carbon for WT2, and 50% for
Carbon Assessment of Timber Frame Wall Types IRISH TIMBER FRAME MANUFACTURERS’ ASSOCIATION 1
carbon impacts of each are clearest when looking at the caused per square metre of wall area. Here it is clearest that wool and render board wall has the lowest carbon emissions with it. The rendered carrier board results in lower carbon than masonry The PIR insulated walls have the highest emissions, in addition to greater impact under other environmental impact indicators (compared to mineral wool)
carbon impacts of each are clearest when looking at the emissions caused per square metre of wall area. Here it is clearest that the mineral wool and render board wall has the lowest carbon emissions associated with it. The rendered carrier board results in lower carbon emissions than masonry. The PIR-insulated walls have the highest carbon emissions, in addition to greater impact under other environmental impact indicators (compared to mineral wool).
The timber frame wall types modelled are insulated with either mineral wool (WT1 and 2) or polyisocyanurate (PIR) insulation (WT3 and 4). They are finished externally with either rendered blockwork (WT1 and 3) or cement-particle board render carrier and render system (WT2 and 4).
A copy of the calculation spreadsheet has been provided to ITFMA along with this report and should be consulted where further detail is required (filename: ITFMA_Wall-types_Carbon_v2.xlsx – referred to hereafter as ‘the Spreadsheet’).
• C2: emissions of transporting materials away from site after demolition.
5 RICS, Property measurement (incorporating International Property Measurement Standards) (2015). practice-6thedition-rics.pdfupholdingprofessional-standards/sector-standards/valuation/code-of-measuring-https://www.rics.org/globalassets/rics-website/media/
Carbon Assessment of Timber Frame Wall Types 2 IRISH TIMBER FRAME MANUFACTURERS’ ASSOCIATION
remain in use forsignificantly longer, but a standard lifespan enables comparison of different projects on the same terms.
This work builds on calculations carried out by Tim Martell for the Passive House Association of Ireland (PHAI) comparing the carbon of different building elements and the resulting operational energy use (those results are not included in this report).
Operational carbon calculations (and combined operational and embodied calculations) are shown in the ‘ITFMA Total CO2’ tab.
• A5: emissions during construction, fuel and energy use, material wastage etc.
• A4: transport of materials to site.
Module B concerns emissions during use of the building:
The operational energy calculations used for the ITFMA work in this report assume the same floor and roof build ups as the PHAI work and use the same reference building (the same areas are used for each external element and for internal floor areas). The PHAI work explored several wall types with differing U values (differing levels of energy
A1-A3: product manufacture, including extraction and processing of raw materials and transport to place of manufacture (cradle to gate emissions).
A full summary of results is given in the Spreadsheet (with key findings included in this report) in the tab ‘ITFMA Results’. Full embodied carbon calculations for WT 1 to 4 – with details of products used as the data source for each element – are found in Table 1 of the ‘ITFMA Embod tab’. Where available, column AA includes a link to source data. A copy of the raw data is included in the same tab from row 996. In cells AA524 to AQ903 full results are given for the whole building embodied carbon assessment with each of the four timber frame Wall Types, with an indicator of the level achieved under the RIAI 2030 challenge. The calculations for the ICF concrete walls (WT 5a and 5b) can be found on the tab ‘ICF Embod’ on the Spreadsheet.
• B4, B5: replacement and refurbishment.
The Spreadsheet
•
Resultsotherwise.are
Life cycle stages
• B1, B2, B3: use, maintenance and repair.
• B6: Operational emissions, resulting from energy used.
Replacement of products and materials over the life of the building is included, based on individual product/material lifespans as stated in their environmental data where available, or using default values
reported as net emissions, both as total tonnes of CO2e released, and standardised to enable comparison by dividing emissions by the Gross Internal Floor Area5 (GIA) (kgCO2e/m2 GIA).
Module C concerns emissions at and after the end of the building’s life.
Module A concerns everything up to completion of the building (also known as the up-front emissions):
CO2e refers to carbon dioxide equivalent emissions, with other gases converted to an amount of CO2 with an equivalent global warming potential (GWP).
efficiency). The wall types for the ITFMA all have a U value of 0.18 W/ m2K; the wall U value used in the operational energy calculations for this work has been adjusted to match this.
As the focus of this work is the emissions caused by the different wall types, emissions are also separately reported per square metre of wall area for each wall type.
• C3/C4: emissions associated with processing and disposal. The processing necessary will depend on the material and whether it is being recycled, incinerated, or landfilled. There may be
For whole building calculations, an allowance is made for the additional emissions generated during both construction and deconstruction, damages etc (lifecycle stage A5 and C1). Replacement and maintenance emissions are included. A5 and C1 emissions are project/building specific and so are excluded from comparisons of the wall types alone.
Carbon emissions as reported in construction product EPDs and calculated in building whole life carbon assessment are split into life cycle stages or modules, as shown in Table 1.
• C1: emissions due to demolition of the building, primarily through fuel use.
Assumptions
• Ventilation by window opening and intermittent extract fans.
Product and construction Use Demolition and disposal Potential benefits/loads beyond building life cycle ManufactureA3A1 CarbonA3A1- storage sitetoTransportA4 ConstructionA5 B3B2,B1,- Maintenance, Repair B5B4,- Replacement, Refurbishment OperationalB6- emissions DemolitionC1 TransportC2 RecycleC3/C4 IncinerationC3/C4 LandfillC3/C4 recycleD incinerationD landfillD 4 Eirgrid, Tomorrow’s Energy Scenarios (TES) TES 2019 Scenario 2: Delayed https://www.eirgridgroup.com/site-files/library/EirGrid/EirGrid-TES-2019-Report.pdfTransition,
• Lighting and other electrical cables, fittings, switches, fans etc.
• Wall build-ups and U values as above.
Module B concerns emissions during use of the building:
• B1, B2, B3: use, maintenance and repair
Module D concerns benefits and loads beyond the lifecycle of the building
Assumptions and Omissions
These can be in the form of avoided fossil fuel use or raw material extraction. These are not included in the main calculations under RICS or EU Levels methodology as there is a high level of uncertainty involved The figures are reported to give an indication of reuse or recycling potential of materials used
further emissions caused by the recycling process itself, and by incineration or landfill.
Module D concerns benefits and loads beyond the lifecycle of the building. These can be in the form of avoided fossil fuel use or raw material extraction. These are not included in the main calculations under RICS or EU Levels methodology as there is a high level of uncertainty involved. The figures are reported to give an indication of reuse or recycling potential of materials used
* Adjusted from the higher U value used in the PHAI work
• Internal walls assumed to be plasterboard on timber stud, with acoustic mineral wool filling.
• Wherever possible, Ireland-specific EPDs have been used.
• Fixed furniture and fittings (with the exception of sanitary ware).
Table 1. Whole life carbon life cycle stages/modules 5 Life cycle stages
• A4: transport of materials to site
• Gross Internal Area (GIA): 83.5 m2.
• 05ud-Roof (insulated at pitch), (U value 0.16 W/m2K)*.
• Project value: UK£172,000 (also from PHAI study). Used to estimate A5 construction emissions.
Module A concerns everything up to completion of the building (also known as the up front emissions):
• B4, B5: replacement and refurbishment.
• B6: Operational emissions, resulting from energy used.
Carbon emissions as reported in construction product EPDs and calculated in building whole life carbon assessment are split into life cycle stages or modules, as shown in Table 1.
Table 1. Whole life carbon life cycle stages/modules.
• C1: emissions due to demolition of the building, primarily through fuel use.
• Air-test result assumed to be 2.95 m3/h/m3 (3.6 air changes per hour).
Carbon Assessment of Timber Frame Wall Types IRISH TIMBER FRAME MANUFACTURERS’ ASSOCIATION 3
• External works.
• Fixings, joist hangers etc. (though wall ties and ICF connecting webs are included).
Module C concerns emissions at and after the end of the building’s life.
• Concrete assumed to be 1% reinforced, with 50% GGBS OPC replacement.
The following items were omitted from calculations:
• 04ud-Roof (insulated at ceiling), (U value 0.14 W/m2K).
• Heating by air source heat pump (included in embodied carbon).
• A1 A3: product manufacture, including extraction and processing of raw materials and transport to place of manufacture (cradle to gate emissions)
• C3/C4: emissions associated with processing and disposal. The processing necessary will depend on the material and whether it is being recycled, incinerated, or landfilled. There may be further emissions caused by the recycling process itself, and by incineration or landfill.
• Treated Floor Area (TFA): 73 m2.
• Roof, soffit and floor build-ups as per PHAI work. For details see U value build-ups in U-values tab of the supplied spreadsheet:
• Operational carbon is calculated using Eirgrid Group’s ‘Delayed Transition’6 energy scenario to avoid underestimating operational carbon.
• 06ud-Soffit.
Omissions
• 10ud-UG2-4 Upgrade Floor: Raft, (U value 0.17 W/m2K).
• Internal floors assumed to be open web easy/posi-joist, with OSB floor surface and plasterboard ceiling, with acoustic mineral wool between joists.
• A5: emissions during construction, fuel and energy use, material wastage etc.
• C2: emissions of transporting materials away from site after demolition.
The Wall Types
Carbon Assessment of Timber Frame Wall Types 4 IRISH TIMBER FRAME MANUFACTURERS’ ASSOCIATION typeswallThe 6 3TypeWall2TypeWall1TypeWall renderboardwool/PIR,mineralTimber,masonrywool/PIR,mineralTimber,Timber,PIR,masonry mmmmmm firelineGyprocfirelineGyprocfirelineGyproc151515 battens)(withCavitybattens)(withCavitybattens)(withCavity353535 VCLVCLVCL studstimberbetweenCavity4030PIRMannokMannokPIR50 90140140studstimberbetweenwoolMineralMineralwoolbetweentimberstudsMannokPIRbetweentimberstuds 3OSBSmartply3OSBSmartply3OSBSmartply999 membranepermeablevapourtightWeathermembranepermeablevapourtightWeathermembranepermeablevapourtightWeather Cavitybattens)(withCavityCavity505050 concrete)dense(mediumBlockworksystemrenderandrenderboardStoVentecconcrete)dense(mediumBlockwork10016100 renderSand/cementrenderSand/cement1515 0.18value:U 2W/mK 0.18value:U 2W/mK 0.18value:U 2W/mK layerstimber-bridgedallin%15fractionTimberlayerstimber-bridgedallin%15fractionTimberlayerstimber-bridgedallin%15fractionTimber 22mpertieswallSS44SSwalltiesperm 22222COkge/mGIAkgCO2e/mwallkgCOe/mGIA arewhichC1andA5(excl. projects)individualtospecific 2e/mCOkg2wall 40.0991.28arewhichC1andA5(excl.house)reference(for projects)individualtospecific
4TypeWallWallType5aWallType5b caseworst-FormworkConcreteInsulatedcasebest-FormworkConcreteInsulatedRenderboardPIR,Timber, mmmmmm plasterboardfirelineGyprocplasterboardfirelineGyprocfirelineGyproc151515 (Neopor)EPS(Neopor)EPSbattens)(withCavity356565 33cement/mkg230GGBS,73%rebar,(0.4%ConcreteVCL)150Concrete(1%rebar,13%GGBS,350kgcement/m)150 (Neopor)EPS(Neopor)EPS25studstimberacrossPIRMannok6565 Neopor)(EPSEWINeopor)(EPSEWIstudstimberbetweenCavity504040 renderSiliconerenderSilicone90studstimberbetweenPIRMannok1010 3OSBSmartply9 membranepermeablevapourtightWeather battens)(withCavity50 systemrenderandrenderboardStoVentec16 0.18value:U 2W/mK 0.18value:U 2W/mK 0.18value:U 2W/mK 22layerstimber-bridgedallin%15fractionTimber44.5Polypropylenewebsperm44.5Polypropylenewebsperm 156.4235.8385.00222222222e/mCOkg2wallkgCOe/mGIAkgCO2e/mwallkgCOe/mGIAkgCOe/mGIAkgCO2e/mwall arewhichC1andA5(excl.house)reference(for projects)individualtospecific 125.69217.33 arewhichC1andA5(excl. projects)individualtospecific tospecificarewhichC1andA5(excl.house)reference(for projects)individual house)reference(for 84.33
222e/mCOkg2wallkgCOe/mGIA 27.8273.2137.2187.03arewhichC1andA5(excl.house)reference(forhouse)reference(for projects)individualtospecific
Carbon Assessment of Timber Frame Wall Types IRISH TIMBER FRAME MANUFACTURERS’ ASSOCIATION 5
Space Heating kWh/m2 GIA / a 2025
the end of a building’s life It remains stored remains in place. Cradle to practical completion
RIAI target Space
Table 2 also indicates the RIAI Climate Challenge level achieved for a domestic building. With all the wall types modelled for this study the reference house meets the RIAI 2030 targets for embodied carbon (2030 target levels <625 kgCO2e/m2 stages A-C, <400 kgCO2e/m2 A1-
concrete-related emissions for Wall Types 1 and 3 (with concrete block masonry) and 5a/b (ICF); the greatest oil-based emissions are from the house built with wall types 3, 4 and 5a/b (greater amounts of PIR or EPS insulation).
Taken together these charts show (unsurprisingly) that the greater the carbon emissions resulting from each wall type: the greater the proportion of total emissions that wall type causes. WT2 (the lowestcarbon timber frame wall type: mineral wool and PIR with render-board) contributes 26% of the total embodied carbon of the whole house, whereas WT5a (the best-case ICF wall, with the greatest proportion of GGBS cement replacement and lowest amount of steel) contributes 42%. WT5b (the worst-case ICF wall) contributes 50% of the total embodied carbon of the whole house.
Operational (same for all options)
storage.Climate
NB: stored CO2 is released at the end of a building’s life It remains stored only while the building remains in place. Cradle to practical completion figures exclude carbon storage.
Table 3 show the operational energy use and resulting carbon emissions for the reference house. This is the same with all wall types modelled for this report. The operational energy use meets the RIAI 2025 Climate Challenge target. Further improvements in U values (including of the walls) would assist in reducing the overall energy use, in combination with reductions in air leakage, and implementation of heat-recovery
8007006005004003002001000 WT1 WT2 WT3 WT4 WT5a WT5b 2e/mCOkg2GIA
/
to
NB: stored CO2 is released at the end of a building’s life. It remains stored only while the building remains in place. Cradle to practical completion figures exclude carbon storage.
Carbon Assessment of Timber Frame Wall Types 6 IRISH TIMBER FRAME MANUFACTURERS’ ASSOCIATION
WT1 -150 -158 -150 -156 -108
Figure 1 shows the combined operational and embodied net emissions of the reference house with each wall type, over a 50 year lifespan
operational CO2e of whole building with different kgCO2/m2 GIA, and total tonnes emitted.
(net emissions) Whole building
TheA5)
A C (50 year lifespan) operational carbon embodied carbon
Space Heating kWh/m2 GIA / a 2025 Heating kWh/m2 TFA a 2e/mCOkg2GIA
Final Energy kWh/m2 TFA / a (excl PV) 64.3 tonnes CO2e (incl PV if any) 20.8 kgCO2e/m² GIA (incl PV if any) 248.8
RIAI target achieved
Figure 2 shows gross embodied emissions of the whole house with each wall type over a 50-year lifespan, split by material type or other emissions source. The split helps visualise differing sources of carbon impacts on each wall type. As might be expected, there are greater
Combined Operational Embodied CO2e Cradle Grave,
Table 3. Operational energy use and resulting emissions, for reference house with wall types 1 to 5.
Figure 1 shows the combined operational and the reference house with each wall type, over
Table 3 show the operational energy use and resulting carbon emissions for the reference house. This is the same with all wall types modelled for this report. The operational energy use meets the RIAI 2025 Climate Challenge target. Further improvements in U values (including of the walls) would assist in reducing the overall energy use, in combination with reductions in air leakage, and implementation of heat recovery ventilation.
Space Heating kWh/m2 TFA / a
(50 year lifespan) operational carbon embodied
carbon emissions caused by construction of each of the six wall types, for the full lifecycle grave, stages A C), and from cradle to practical (lifecycle stages A1 A5) – also known as
55.272.7
Combined Operational and Embodied CO2e (net emissions) Whole building Cradle to Grave, A C (50 year lifespan)
Figureventilation.1shows
Figure 1. Combined net operational and embodied emissions of whole house with each wall type, 50 year lifespan.
highest ranking under the challenge, with 2025 aim.
Table 3. Operational energy use and resulting emissions, for reference house with wall types 1 to 5.
8007006005004003002001000 WT1 WT2 WT3 WT4
8
operational carbon embodied carbon
whole house with different
Table 3. Operational energy use and resulting emissions, for reference house with wall types 1 to 5.
the combined operational and embodied net emissions of the reference house with each wall type, over a 50-year lifespan.
55.272.7
Table 3 show the operational energy use and resulting carbon emissions for the reference house. This is the same with all wall types modelled for this report. The operational energy use meets the RIAI 2025 Climate Challenge target. Further improvements in U values (including of the walls) would assist in reducing the overall energy use, in combination with reductions in air leakage, and implementation of heat recovery ventilation.
As the focus of this report is the different wall types, the following charts (Figure 3) explore the contribution of each wall type to the total embodied carbon of the reference house.
Table 2 All categories embodied and operational CO2e of whole building with different wall types, standardised to kgCO2/m2 GIA, and total tonnes emitted.
and
WT2 WT3 WT4 WT5a WT5b 25.1 23.9 25.4 24.9 30.9 36.0 300.3 286.5 304.6 298.3 369.7 430.7 2030 2030 2030 2030 2030 2030 227 224 232 238 254 317
Headline Figures: whole house with different wall types
Contribution of the walls
Final Energy kWh/m2 TFA / a (excl PV) 64.3 tonnes CO2e (incl PV if any) 20.8 kgCO2e/m² GIA (incl PV if any) 248.8
Table 2 gives the embodied carbon emissions caused by construction of the reference dwelling with each of the six wall types, for the full lifecycle of the building (cradle to grave, stages A C), and from cradle to practical completion of the building (lifecycle stages A1 A5) – also known as Upfront Emissions.
-108 45.8 44.7 46.2 45.7 51.6 56.7
Table 2 also indicates the RIAI Climate Challenge level achieved for a domestic building. With all the wall types modelled for this study the reference house meets the RIAI 2030 targets for embodied carbon (2030 target levels <625 kgCO2e/m2 stages A C, <400 kgCO2e/m2 A1 A5)
Operational (same for all options) Operational and Embodied CO2e Cradle Grave,
to
55.272.7 Final Energy kWh/m2 TFA / a (excl PV) 64.3 tonnes CO2e (incl PV if any) 20.8 kgCO2e/m² GIA (incl PV if any) 248.8 Space Heating kWh/m2 GIA / a 2025 RIAI target achieved Space Heating kWh/m2 TFA / a 8007006005004003002001000 WT1 WT2 WT3 WT4 WT5a WT5b 2e/mCOkg2GIA Combined
Operational (same for all options)
Embodied WT1 WT2 WT3 WT4 WT5a WT5b All categories, tonnes CO2e A-C 25.1 23.9 25.4 24.9 30.9 36.0 300.3 286.5 304.6 298.3 369.7 430.7 2030 2030 2030 2030 2030 2030 227 224 232 238 254 317 -150 -158 -150 -156 -108 -108 45.8 44.7 46.2 45.7 51.6 56.7 RIAI target achieved A1-A5: Cradle to practicalkgCOcompletion2e/m²GIA A-A3 stored CO2 kgCO2e/m² GIA Combined operational andtonnesembodied,CO2e RIAI kgCO2e/m² GIA
2030 Target is the highest ranking under the challenge, with 2025 representing an intermediate aim.
Table 2. All categories embodied and operational CO2e of whole building with different wall types, standardised to kgCO2/m2 GIA, and total tonnes emitted.
(net emissions) Whole building
The 2030 Target is the highest ranking under the challenge, with 2025 representing an intermediate aim.
Figure 1. Combined net operational and embodied emissions type, 50 year lifespan.
Challenge level achieved for a the wall types modelled for this study the RIAI 2030 targets for embodied carbon (2030 stages A C, <400 kgCO2e/m2 A1 A5)
Headline Figures: whole house with different wall types
Table 3 show the operational energy use and for the reference house. This is the same with this report. The operational energy use meets Challenge target. Further improvements in U walls) would assist in reducing the overall energy with reductions in air leakage, and implementation ventilation.
Figure 1. Combined net operational and embodied emissions of whole house with each wall type, 50 year lifespan.
Table 3. Operational energy use and resulting emissions, 1 to 5.
Table 2 gives the embodied carbon emissions caused by construction of the reference dwelling with each of the six wall types, for the full lifecycle of the building (cradle to grave, stages A-C), and from cradle to practical completion of the building (lifecycle stages A1-A5) – also known as Upfront Emissions.
60%50%40%30%20%10%0% WT1 WT2 WT3 WT4 WT5a WT5b COtotalof%2e
Carbon Assessment of Timber Frame Wall Types IRISH TIMBER FRAME MANUFACTURERS’ ASSOCIATION 7
D: potential benefits/loads beyond the building's life cycle (whole building different wall types)
-0.50-1.00-1.50-2.00-2.50-3.000.000.50 WT1 WT2 WT3 WT4 WT5a WT5b 2/mkgCO2wall
Taken together these charts show (unsurprisingly) that the greater the carbon emissions resulting from each wall type: the greater the
composite composite composite composite composite composite concrete concrete concrete concrete concrete concrete inert inert inert inert inert inert mineral wool mineral wool mineral wool mineral wool mineral wool mineral wool oil based oil based oil based oil based oil based oil based steel steel steel steel steel steel timber timber timber timber timber timber timber storage timber storage timber storage timber storage timber storage timber storage A4 Transport to siteA4Transport to siteA4Transport to siteA4Transport to siteA4Transport to siteA4Transport to site A5 Construction A5 Construction A5 Construction A5 Construction A5 Construction A5 Construction B Use B Use B Use B Use B Use B UseC Demolition & DisposalCDemolition & DisposalCDemolition & DisposalCDemolition & DisposalCDemolition & DisposalCDemolition & Disposal D Benefits D Benefits D Benefits D Benefits D Benefits D Benefits-150-250-5050150250350450 WT1 WT2 WT3 WT4 WT5a WT5b 2e/mCOkgStoredCarbon<2GIACarbonEmitted> Embodied CO2e (gross emissions) Whole building Cradle to Grave A-C (50 year lifespan) D Benefits C Demolition & Disposal B compositeconcreteinertmineraloilsteeltimbertimberA4A5UseConstructionTransporttositestoragebasedwool -49-50-51-52-53-54-55-56 WT1 WT2 WT3 2/mkgCO2GIA D: potential benefits/loads beyond the building's (whole building with different 60%50%40%30%20%10%0% WT1 WT2 WT3 COtotalof%2e Contribution of walls buiding embodied Figure 3. Charts exploring the contribution of the different wall types to whole house carbon emissions. 9 wall type over a 50 year whole house with each or emissionstheresourcesotherofcarbonaregreater(withconcreteblockarefromtheamountsofPIRorEPS
Disposal lifespan) D Benefits C Demolition & Disposal B compositeconcreteinertmineraloilsteeltimbertimberA4A5UseConstructionTransporttositestoragebasedwool -49-50-51-52-53-54-55-56 WT1 WT2 WT3 WT4 WT5a WT5b 2/mkgCO2GIA
with
Contribution of walls to whole buiding embodied CO2e
Contribution of
As the focus of this report (Figure 3) explore the contribution embodied carbon of the
Figure 3. Charts exploring the contribution emissions.
Contribution of the walls
Figure 3. Charts exploring
Figure 2 shows gross embodied emissions of the whole house with each wall type over a 50 year lifespan, split by material type or other emissions source. The split helps visualise differing sources of carbon impacts on each wall type. As might be expected, there are greater concrete related emissions for Wall Types 1 and 3 (with concrete block masonry) and 5a/b (ICF); the greatest oil based emissions are from the house built with wall types 3, 4 and 5a/b (greater amounts of PIR or EPS insulation).
As the focus of this report is the different wall types, the following charts (Figure 3) explore the contribution of each wall type to the total embodied carbon of the reference house. the contribution of the different wall types to whole house carbon
Figure 2. Gross embodied emissions of the whole house with each wall type over a 50-year lifespan, split by material type or other emissions source.Figure 2. Gross embodied emissions of the whole house with each wall type over a 50 year lifespan, split by material type or other emissions source.
emissions.
140120100806040200 WT1 WT2 WT3 WT4 WT5a WT5b 2/mkgCO2wall
Taken together these charts carbon emissions resulting
Wall carbon only: embodied CO2e per m2 of wall
D: potential benefits/loads beyond the building's life cycle (per m2 of wall)
Separated results for each wall type
the clearest comparison of the carbon emissions of the different wall types. The walls with the lowest embodied carbon are WT2
WT5a has associated carbon emissions per m2 of wall 3 times higher than WT2.
This report and associated calculations are primarily concerned with the carbon impacts of the different wall types, but other environmental impacts should also be considered when making material choices. Figure 4 shows some of the other environmental impacts reported in EPDs of several insulation materials, at a thickness of material to provide an R value of 3 m2K/W.
WT5a 13.06 156.42 42% WT5b 18.15 217.33 50% excl. A5 C1 which are specific to individual
WT4 7.10 85.00 28%
Table 4 shows the separated results for each wall type, both as contribution to the whole house emissions, and separated per square metre of external wall area (also shown in the top right chart of Figure 3)
D figures tell a mixed story (potential beyond a building’s life cycle). While Wall types benefits per m 2 of wall area, WT5a shows a much benefit. This benefit comes from the carbonation crushed up to recycle at end of life (it absorbs Type 5b also has this benefit but it is offset by (emissions) caused by processing the greater causing WT5b to be the only wall to show a net
WT3 7.62 91.28 30%
Table 4. Separated results for each wall type: contribution to whole house in tonnes and kg/m2 of GIA, and separated per m2 of wall surface area.
TheWT2.module
The module D figures tell a mixed story (potential benefits and loads beyond a building’s life cycle). While Wall types 1 to 4 show small benefits per m2 of wall area, WT5a shows a much greater potential benefit. This benefit comes from the carbonation of concrete once it crushed up to recycle at end of life (it absorbs carbon at that point); wall Type 5b also has this benefit but it is offset by greater stage D loads (emissions) caused by processing the greater amount of steel in WT5b, causing WT5b to be the only wall to show a net load at module D.
projects0.11-0.04-0.04-0.04 For reference house Benefits and loads beyond building lifecycle (kgCO 2e/m2 wall)kgCO 2e/m2 of wall * % carbontotalof
The results per m 2/wall exclude A5 (construction) and C1 (demolition) emissions as these are specific to each building and vary depending on
WT5a has associated carbon emissions per m
Separated results for each wall type
lasting for the lifetime of the building. There would be the case, with replacement of the external possible in both cases without replacing the masonry board, over the 50 year lifespan
crushed up to recycle at end of life (it absorbs carbon at that point); wall Type 5b also has this benefit but it is offset by greater stage D loads (emissions) caused by processing the greater amount of steel in WT5b, causing WT5b to be the only wall to show a net load at module D.
tonnestotal kgCO 2e/ m2 GIA
This report and associated calculations are primarily carbon impacts of the different wall types, but impacts should also be considered when making
125.6984.3335.8340.0927.8237.21 -2.40-0.04 * =
Figure 5 shows the relative contribution to embodied CO2e from different material types under each wall type.
Figure 6 shows the A-C emissions of each wall type split by lifecycle/ module stage and main material or other emissions source. It shows the differing sources and magnitude of potential loads and benefits in each wall type.
Table 4. Separated results for each wall type: contribution to whole house in tonnes and kg/m2 of GIA, and separated per m2 of wall surface area.
In terms of insulation materials and their impact the two wall types using primarily mineral wool insulation (WT1 and WT2) have lower embodied carbon than their counterparts which use mainly PIR foam (WT3 and WT4). This could potentially be reduced further by avoiding use of any PIR in WT1 and WT2.
Carbon Assessment of Timber Frame Wall Types 8 IRISH TIMBER FRAME MANUFACTURERS’ ASSOCIATION
This result is dependent on both the render board and the masonry outer lasting for the lifetime of the building. There is good evidence that this would be the case, with replacement of the external protective render possible in both cases without replacing the masonry or the render board, over the 50-year lifespan.
GGBS cement replacement and lowest amount of steel) contributes 42%. WT5b (the worst case ICF wall) contributes 50% of the total embodied carbon of the whole house.
WT1 7.27 87.03 29%
Thscale.isgives
In terms of insulation materials and their impact primarily mineral wool insulation (WT1 and WT2) carbon than their counterparts which use mainly WT4). This could potentially be reduced further PIR in WT1 and WT2.
WT2 6.11 73.21 26%
and
Table 4 shows the separated results for each wall type, both as contribution to the whole house emissions, and separated per square metre of external wall area (also shown in the top right chart of Figure 3). The results per m2/wall exclude A5 (construction) and C1 (demolition)emissions as these are specific to each building and vary depending on scale.
The module D figures tell a mixed story (potential benefits and loads beyond a building’s life cycle). While Wall types 1 to 4 show small benefits per m2 of wall area, WT5a shows a much greater potential benefit. This benefit comes from the carbonation of concrete once it
Carbon Assessment of Timber Frame Wall Types IRISH TIMBER FRAME MANUFACTURERS’ ASSOCIATION 9 11 ofEPDsinreportedimpactsenvironmentalothertheofsomeshows4 Ranprovidetomaterialofthicknessaatmaterials,insulationseveral 3ofvaluem 2 K/W embodiedtocontributionelativetheshowsFigure5rCO 2 frome type.walleachundertypesmaterialdifferent bysplittypewalleachofemissionsCAtheshows6Figure Itsource.emissionsotherormaterialmainandstagelifecycle/module andloadspotentialofmagnitudedifferingtheshowssourcesand type.walleachinefitsben 024681012 flexiWoodfibrefibreCelluloseEPSwoolMineralPIR kg2COeq (GWP)PotentialWarmingGlobal -50050100150200250 flexiWoodfibrefibreCelluloseEPSwoolMineralPIR MJ Renewable/NonEnergyPrimaryRenewableTotal (PERT/PENRT) PENRTPERT 0.00000000.00000010.00000010.00000020.00000020.00000030.00000030.00000040.0000004 flexiWoodfibrefibreCelluloseEPSwoolMineralPIR kgCFC11eq (ODP)PotentialDepletionOzone 0.000.010.020.030.040.050.06 flexiWoodfibrefibreCelluloseEPSwoolMineralPIR kg2SOeq (AP)PotentialAcidification 0.0000.0020.0040.0060.0080.0100.012 flexiWoodfibrefibreCelluloseEPSwoolMineralPIR kg(PO)43eq (EP)PotentialEuthrophication 0.0000.0050.0100.0150.0200.0250.0300.035 flexiWoodfibrefibreCelluloseEPSwoolMineralPIR kg4H2Ceq (POCP)OzonetroposphericofpotentialFormation 0.000000.000010.000020.000030.000040.000050.000060.000070.000080.00009 flexiWoodfibrefibreCelluloseEPSwoolMineralPIR kgSbeq (ADPE)ElementsPotentialDepletionAbiotic 050100150200250 flexiWoodfibrefibreCelluloseEPSwoolMineralPIR MJnetcalorificvalue (ADPF)FossilPotentialDepletionAbiotic 2m3ofvalueRthicknessatmaterialsinsulationseveralforindicatorsimpactenvironmentalEPD.Figure4estoachieveanK/W.m3ofvalueRanachievetothicknessesatmaterialsinsulationseveralforindicatorsimpactenvironmentalEPD4.FigureK/W. WTright,to(lefttype.walleachundertypesmaterialfromeCOembodiedtocontributionRelative5.Figure21,WT2WT3,WT4,WT5a,WT5b). 305070 InternalFloorArea COEmbodied2e:WT5a 7090110130150 InternalFoorArea COEmbodied2e:WT5b 305070 InternalFloorArea COEmbodied2e:WT1 305070 InternalFoorArea COEmbodied2e:WT2 305070 InternalFloorArea COEmbodied2e:WT3 305070 InternalFloorArea COEmbodiede:WT4 inertconcrete basedoilwoolmineralsteel0mber inert 0mberbasedoilwoolmineral concrete inert basedoil 0mber basedoilinert 0mber concrete inertbasedoil steel concrete steelbasedoilinert (lefttype.walleachundertypesmaterialfromembodiedtocontributionRelative.Figure5CO2etoright,WT1,WT2,WT3,WT4,WT5a,WT5b).
COEmbodied2e:WT2
sourceemissionsotherormaterialmainandstage/modulelifecyclebysplittype,walleachofcarbonEmbodied.6Figure( emissionshighertodueWT5bforscalechartofchangenoteNB: ).
Carbon Assessment of Timber Frame Wall Types 10 IRISH TIMBER FRAME MANUFACTURERS’ ASSOCIATION
All the timber frame wall types result in significantly lower carbon emissions than the Insulated Concrete Formwork (ICF) walls. These are shown to have the highest emissions even in the best case ICF scenario WT5a (which allows the smallest possible amount of steel reinforcement and a high proportion of GGBS cement replacement in the ICF). WT5a has more than twice the carbon emissions per square metres of wall than any of the timber frame options explored, with WT5b having over 3 times the emissions of the timber frame options.
12 -50-30-1010305070 CO2StoredAModuleModuleBModuleC 2e/m2kgCOGrossInternalFloorArea stageLifecycleCOEmbodied2e:WT5a ConcreteA:ModuleModuleA:Inert basedOilA:ModuleModuleA:Steel (maintenance/replacement)UseBsitetoTransportA4A:Module Disposal&DemolitionC -50-30-101030507090110130150 CO2StoredAModuleModuleBModuleC 2e/m2kgCOGrossInternalFoorArea stageLifecycleCOEmbodied2e:WT5b ConcreteA:ModuleModuleA:Inert basedOilA:ModuleModuleA:Steel (maintenance/replacement)UseBsitetoTransportA4A:Module Disposal&DemolitionC -50-30-1010305070 CO2StoredAModuleModuleBModuleC 2e/m2kgCOGrossInternalFloorArea stageLifecycleCOEmbodied2e:WT1 ConcreteA:ModuleModuleA:Inert basedOilA:ModulewoolMineralA:Module SteelA:ModuleModuleA:Timber sitetoTransportA4A:ModuleCOStoredTimber Disposal&DemolitionC(maintenance/replacement)UseB -50-30-1010305070 CO2StoredAModuleModuleBModuleC 2e/m2kgCOGrossInternalFoorArea stageLifecycle
Conclusion
There are clear differences in the embodied carbon emissions associated with the different wall types. While arguably relatively small difference per square metre the cumulative impact of the differences would be significant. The walls externally clad with a render-board finish result in 9.4 kg (mineral wool wall) and 4.3 kg (PIR wall) fewer carbon emissions per square metre of wall surface than their masonry clad counterparts.
When considering the emissions in relation to the reference house, none of the options enable it to achieve the RIAI 2030 Climate Challenge target for operational energy without further measures; all meet the 2025 target. All the wall types meet the RIAI 2030 embodied carbon targets for whole life (A-C) carbon.
ConcreteA:ModuleModuleA:Inert basedOilA:ModulewoolMineralA:Module SteelA:ModuleModuleA:Timber COStored ₂ sitetoTransportA4A:ModuleTimber Disposal&DemolitionC(maintenance/replacement)UseB -50-30-1010305070 CO2StoredAModuleModuleBModuleC 2e/m2kgCOGrossInternalFloorArea stageLifecycleCOEmbodied2e:WT3 ConcreteA:ModuleModuleA:Inert basedOilA:ModulewoolMineralA:Module SteelA:ModuleModuleA:Timber sitetoTransportA4A:ModuleCOStoredTimber Disposal&DemolitionC(maintenance/replacement)UseB -50-30-1010305070 CO2StoredAModuleModuleBModuleC 2e/m2kgCOGrossInternalFloorArea stageLifecycleCOEmbodied2e:WT4 ConcreteA:ModuleModuleA:Inert basedOilA:ModulewoolMineralA:Module SteelA:ModuleModuleA:Timber sitetoTransportA4A:ModuleCOStoredTimber Disposal&DemolitionC(maintenance/replacement)UseB
The walls primarily insulated with mineral wool result in lower carbon emissions than their counterparts primarily insulated with PIR board, with the difference most pronounced in the case of the render board walls. The combination of mineral wool insulation and render board has the lowest carbon emissions of the wall types investigated for this study, with PIR and masonry resulting in the highest carbon emissions.
(lefttype.walleachundertypesmaterialfromembodiedtocontributionRelative.Figure5CO2etoright,WT1,WT2,WT3,WT4,WT5a,WT5b).
WTforscalechartofchangenote(NB:sourceemissionsotherormaterialmainandstage/modulelifecyclebysplittype,walleachofcarbonEmbodied6.Figure5bduetohigheremissions).
While these calculations were an important start – an opportunity to compare apples with apples by assessing the same house against different build approaches – it took in a comparatively small number of variants. The PHAI and AECB therefore agreed to make the calculations available to any third parties who wish to assess other variants against the house type, provided they agree to share the results for further
Issue 38 of Passive House Plus included an article, Six of one, which took a typical Irish house type and analysed the embodied carbon required to build it – assessing a number of variables for wall types and foundations. The house design in question – a 76 m2 end-of-terrace unit provided by Cork City Council – was assessed using the PHribbon embodied carbon calculation tool, in a collaboration between the Passive House Association of Ireland (PHAI), which funded the work, and the Association for Environment Conscious Building (AECB).
REPORT
Frame Manufacturers Association (ITFMA) has taken the opportunity to assess four additional timber frame wall variants against the house type – essentially including timber frame with a fire-rated plaster board and either mineral wool or PIR insulation, and in both cases either rendered block or a recycled glass render board and render system. The ITFMA commissioned sustainable building consultant John Butler to produce a report on the different wall type variants – along with an insulating concrete formwork (ICF) system –and provided draft results to Passive House Plus for this article.
cradle-to-gravefoundations.numbercarbonIrishofeend-of-terCouncil–embodiedcollaborationAssociationofwork,andConsciouscalwallsexterrenderframewallboard.importapplesagainstcomPHAIcalcuwhowishtype,forfurManufacturersAsopportunitywallvariincludboardinsulation,andrecysystem.e
At the risk of death by tables, the 11 vari ants are included here, to show the build-ups
The analysis included cradle-to-grave calculations for wall types including cavity walls (with rendered block or brick externally), externally insulated blockwork (with either render or brick slip) and an I-beam timber frame wall with cellulose insulation and a render board.
in each case. While the full ITFMA report
olition (at end of life), are typically calculated based on the project cost, based on default g ures. In the absence of speci c costs for the var ious wall build-ups, these aspects were omitted.
Consideration was given to excluding emis sions
11 concrete and frame wall specs number crunched
Where a material was Irish-made – as most materials in the analysis are
ther analysis to evolve the ICF analysis into two scenarios – including high and low em bodied carbon variants.
from transporting the materials from
carbonINSIGHTof
House Plus published an in-depth assessment comparing including five wall types to a typical Irish house. To enable the compare a broader range of build options, we now expand that addition of four timber frame wall types and two insulated systems. By Jeff Colley included an typical
Last year Passive House Plus published an in-depth assessment comparing the build specs including five wall types to a typical Irish house. To enable the industry to fairly compare a broader range of build options, we now expand that analysis with the addition of four timber frame wall types and two insulated concrete formwork systems.
Consideration was given to excluding emissions from transporting the materials from factory gate to site (A4) from the calculations for this article, in part due to the diculty in accurately calculating transport distances for concrete products, in the absence of environmental product declarations (EPDs) for many specific products. (For instance, in the case of a concrete block this would involve speculating on where the cement, sand and aggregate were sourced, calculating distance, freight type – and how heavily laden the vehicle is, including return trips – to and from the blockwork manufacturer, and calculating the ratio of each material used). In the end, transport default data from the RICS whole life carbon methodology was used, which suggests default distances for locally, nationally, and mainland Europe manufactured products of 50, 300 and 1,500 km by road, and points to UK government data for emissions from a range of road freight scenarios.
Thedissemination.IrishTimber
As the embodied carbon explainer on p75 reveals, building life cycle assessments typically include three modules – A (cradle to practical completion), B (use phase, typically excluding operational energy and water use) and C (end of life). In this case, two sections of modules have been omitted. Modules A5 and C1 – which respectively deal with emissions released via construction (e.g. onsite activity) and demolition (at end of life), are typically calculated based on the project cost, based on default figures. In the absence of specific costs for the various wall build-ups, these aspects were omitted.
Up to Embodied11carbon of 11 concrete and timber frame wall specs number crunched
Carbon Assessment of Timber Frame Wall Types 12 IRISH TIMBER FRAME MANUFACTURERS’ ASSOCIATION
At the risk of death by tables, the 11 variants are included here, to show the build-ups in each case. While the full ITFMA report will assess wall build-ups to achieve U-values of 0.18 and 0.15, for this article only values of 0.18 were used. Eleven variants may also be a lot to take onboard in one article – let alone 22.
The wall build-ups were calculated to a U-value of 0.18, the backstop for walls under Ireland’s 2019 Technical Guidance Document for Part L of the building regulations, and the five build-ups from the earlier PHAI/ AECB analysis were adapted to meet the same U-value, to enable fairer comparison. For this article, Passive House Plus commissioned further analysis to evolve the ICF analysis into two scenarios – including high and low embodied carbon variants.
Mineral wool between timber studs 140 OSB 3 9
Fire-rated plasterboard 15 Cavity (with battens) 35
325
Fire-rated plasterboard 15 Cavity (with battens) 35
Battens @ 600C 25
Cavity between timber studs 50 PIR between timber studs 90 OSB 3 9
Renderboard & render system 16
Fire-rated plasterboard 15 Cavity (with battens) 35
e timber frame variants tended to include more materials from continental Europe, but this doesn’t come with a signi cant embodied carbon penalty via transport, due to the lighter material weight compared to concrete prod ucts. By way of example, option 5, the I-beam timber frame system with cellulose, generally assumes timber and timber-based products from Sweden, with the exception of Irish-made cellulose and OSB. Much of the imported structural timber used in Ireland comes direct from the south of Sweden by relatively low carbon sea freight, but as the article supposes
UK averages, the local journeys appear to be circa 50 per cent laden trucks, due to consideration of return journeys, which are presumably largely empty for local trips. This means that the 50 km local trips are effectively assumed to be from depots circa 25 km from the site. The 300 km national and 1,500 km European journeys assume roughly 75 per cent laden artics, reflecting a reduced likelihood of empty return journeys.
Wall single leaf block with brick slipsmm
Blockwork 215
type Externally3insulated single leaf block, rendered mm Plaster 13 Blockwork 215 Sand / cement scratch coat 10 EPS 160 Silicone render 6 Total 404
Timber frame, mineral wool/ PIR, rendered block mm
Cavity between timber studs 30
Fire-rated plasterboard type
Mineral wool between timber studs 110 OSB 3 9
Total 290
Embodied C02e of 11 wall variants
Total 368
Wall
Fire-rated plasterboard 15
PIRVCL 15
Total 383
Cavity between timber studs 50 PIR between timber studs 90 OSB 3 9
Weather tight vapour permeable membrane Cavity (with battens) 50 Renderboard and render system 16
Wall type Insulated10concrete
15 EPS 75 Concrete (1% rebar, 28/35 RC, CEM I) 150 Polypropylene webs EPS 75 Render system 10 Total 325 Wall
ph+ | up to 11 insight | 73 INSIGHT ITFMA EMBODIED CARBON REPORT
Wall
Based on 2021 UK averages, the local jour neys appear to be circa 50 per cent laden trucks, due to consideration of return journeys, which
– it was assumed to travel 300 km nationally by articulated truck, and 50 km locally by rigid truck. With the exception of the OSB and cellulose insulation, the timber and timber-based products were assumed to be from mainland Europe, along with the mineral wool insulation, render board system, EWI silicone render and the adhesive for the EWI brick slip Basedsystem.on2021
Weather tight vapour permeable membrane Cavity 50
15 EPS 75 (0.4%Concreterebar, 20/25 RC, CEM III with 70% GGBS) 150 Polypropylene webs EPS 75 Render system 10
type 2 Cavity wall, PIR, brick outer mm Plaster 13 Blockwork 100 PIR 100 Residual cavity 40 Brick 103 Total 355
Given the lack of EPDs for Irish concrete blocks, figures for a medium
The timber frame variants tended to include more materials from continental Europe, but this doesn’t come with a significant embodied carbon penalty via transport, due to the lighter material weight compared to concrete products. By way of example, option 5, the I-beam timber frame system with cellulose, generally assumes timber and timber-based products from Sweden, with the exception of Irishmade cellulose and OSB. Much of the imported structural timber used in Ireland comes direct from the south of Sweden by relatively low carbon sea freight, but as the article supposes 1,500 km truck journeys were instead made, with an extra 50 km locally to deliver to site, it would have added 326 kg CO2e, compared to 86 kg based on 300 km national and 50 km local transport.
are presumably largely empty for local trips. is means that the 50 km local trips are e ec tively assumed to be from depots circa 25 km from the site. e 300 km national and 1,500 km European journeys assume roughly 75 per cent laden artics, re ecting a reduced likeli hood of empty return journeys.
Airtight OSB 12 Cellulose in I-beams 190
Weather tight vapour permeable membrane Cavity 50
Carbon Assessment of Timber Frame Wall Types IRISH TIMBER FRAME MANUFACTURERS’ ASSOCIATION 13
Plaster 13
Total 428
Battens, counterbattens 50
Total
1,500 km truck journeys were instead made, with an extra 50 km locally to deliver to site, it would have added 326 kg CO2e, compared to 86 kg based on 300 km national and 50 km localGiventransport.thelack of EPDs for Irish concrete blocks, gures for a medium density block from the British Precast Association were used, albeit with national transport assumptions. Also, the concrete mix calculations for the ICF system were done prior to the Cement Man ufacturers of Ireland obtaining an EPD for CEM I, and were therefore instead based on an averaged portland cement EPD by the UK’s Mineral Products Association. is meant the cement had a value of 846 kg CO2e/tonne, compared to CMI’s values of 723 kg CO2e/ tonne for CEM I, or 698 kg for CEM II. If the calculations were redone, it’s likely the ICF worst case would have reduced by over one
Wall
Wall type 5
Fire-rated plasterboard
default data from the RICS whole life carbon methodology was used, which suggests default distances for locally, nationally, and mainland Europe manufactured products of 50, 300 and 1,500 km by road, and points to UK govern ment data for emissions from a range of road freightWherescenarios.amaterial was Irish-made – as most materials in the analysis are – it was assumed to travel 300 km nationally by articulated truck, and 50 km locally by rigid truck. With the ex ception of the OSB and cellulose insulation, the timber and timber-based products were assumed to be from mainland Europe, along with the mineral wool insulation, render board system, EWI silicone render and the adhesive for the EWI brick slip system.
PIRVCL 30
Wall type 7
type Externally4insulated
EPS 160 Adhesive 10 Brick slip 20
WF sheathing 22
Wall type 6
Blockwork (medium dense concrete) 100 Sand / cement render 19
Blockwork (medium dense concrete) 100 Sand / cement render 19
Sand / cement scratch coat 10
I-beam timber frame, cellulose, renderboard mm
Foil-faced VCL
Insulated11concrete formwork improved case mm
type 1 Cavity wall, PIR, rendered block mm Plaster 13 Blockwork 100 PIR 110 Residual cavity 10 Blockwork 100 Sand / cement render 19 Total 352
Wall type 9 Timber frame, PIR, renderboard mm
Total 295
PIRVCLacross timber studs 25
Timber frame, mineral wool/ PIR, renderboard mm
Total 303
Weather tight vapour permeable membrane Cavity (with battens) 50 Renderboard and render system 16
Fire-rated plasterboard 15 Cavity (with battens) 35
Wall type 8 Timber frame, PIR, rendered block mm
formwork base case mm
A 50-year building design life was assumed, as per the EU Level(s) sustainable building framework. e render board and render system used for three of the timber frame variants was assumed to last for the lifespan of the building – though as the EPD for the system makes clear, this assumption is dependent on the quality of installation, taking account of rainproof connections to other buildings or building parts. Similarly, the silicon render system used on the two ICF variants and on the rendered EWI system were also considered to last for the life of the building, although the EPD in this case listed a design life for the outer layers of the system of 25 to 50 years, depending on location, construction and material quality, while also recommending repainting a er 15 to 20 years. Repainting and retouching of render systems was omitted in all scenarios, including the sand/cement render, which was assumed to have a 30-year lifespan. Interior painting and repainting were omitted in all cases. Had a 60-year lifespan been assumed instead, as per the UK RICS methodology, the results may have di ered in some cases – depending on what assumptions are made about component lifespan.
Sixth place and the best result for a concrete-based system goes to wall type 3, the block on at with EPS external insulation and silicone render, which at 8.2 tonnes adds over a tonne compared to the worst performing timber frame variant – and double the score of wall type 5.
Wall type 5 – the I-beam timber frame wall with cellulose insulation and a render board –is the clear winner at 4.1 tonnes from A-C. is wall type is also the only variant where more CO2 is sequestered in the walls at the point of practical completion than was released in the manufacture and transport of the wall materials to site. It’s important to note that this sequestered CO2 is assumed to be released at the end of the 50-year design life in the life cycle assessment (LCA), but if the walls were to last in excess of 100 years, this CO2 would remain sequestered for that time. Planners permitting, greater reductions still could potentially be achieved by use of lower embodied carbon
e cavity wall variants also bene ted from this emissivity – with the foil facing on the PIR facing into unventilated cavities.
cavity wall (wall type 1) comes in seventh at 8.9 tonnes, with brick-clad cavity wall (wall type 2) at 9.8 tonnes – re ecting the high embodied carbon of brick manufacturing.
Rendered5.
A 50-year building design life was assumed, as per the EU Level(s) sustainable building framework. The render board and render system used for three of the timber frame variants was assumed to last for the lifespan of the building – though as the EPD for the system makes clear, this assumption is dependent on the quality of installation, taking account of rainproof connections to other buildings or building parts. Similarly, the silicon render system used on the two ICF variants and on the rendered EWI system were also considered to last for the life of the building, although the EPD in this case listed a design life for the outer layers of the system of 25 to 50 years, depending on location, construction and material quality, while also recommending repainting after 15 to 20 years. Repainting and retouching of render systems was omitted in all scenarios, including the sand/cement render, which was assumed to have a 30-year lifespan. Interior painting and repainting were omitted in all cases. Had a 60-year lifespan been assumed instead, as per the UK RICS methodology, the results may have differed in some cases – depending on what assumptions are made about component
density block from the British Precast Association were used, albeit with national transport assumptions. Also, the concrete mix calculations for the ICF system were done prior to the Cement Manufacturers of Ireland obtaining an EPD for CEM I, and were therefore instead based on an averaged portland cement EPD by the UK’s Mineral Products Association. This meant the cement had a value of 846 kg CO2e/tonne, compared to CMI’s values of 723 kg CO2e/ tonne for CEM I, or 698 kg for CEM II. If the calculations were redone, it’s likely the ICF worst case would have reduced by over one tonne of CO2e.
Thelifespan.five
e clear outlier from these 11 wall types is the higher embodied carbon variant of (wall type 10) bringing up the rear at 15 tonnes.
e second and third best results go to two timber frame walls with render board nishes, wall type 7 and 9, with the mineral wool/PIR insulated version (5.0 tonnes) scoring better than the PIR-only variant (5.2 tonnes). Wall type 6 – timber frame with mineral wool/PIR and blocker outer – comes in at 6.4 tonnes, while wall type 8, 8 – a PIR insulated timber frame wall with rendered block cladding – comes in at 6.6 tonnes. One point to note here: the timber frame variants 7-9 bene t signi cantly from the very low emissivity levels assumed for the foil-faced PIR insulation and foil-faced VCLs and membranes, where these materials were facing unventilated cavities, in line with ISO 6946:2017. is meant signicantly reduced insulation thicknesses are required to achieve the 0.18 U-value backstop.
and transport of the wall materials to site. It’s important to note that this sequestered CO2 is assumed to be released at the end of the 50year design life in the life cycle assessment (LCA), but if the walls were to last in excess of 100 years, this CO2 would remain sequestered for that time. Planners permitting, greater reductions still could potentially be achieved by use of lower embodied carbon external cladding, such as charred timber cladding – which can offer the dual benefit of low upfront emissions and 100-year plus lifespans.
Wall type 5 – the I-beam timber frame wall with cellulose insulation and a render board – is the clear winner at 4.1 tonnes from A-C. This wall type is also the only variant where more CO2 is sequestered in the walls at the point of practical completion than was released in the manufacture
Carbon Assessment of Timber Frame Wall Types 14 IRISH TIMBER FRAME MANUFACTURERS’ ASSOCIATION
Passive House Plus intends to add other build specs to this comparison in future issues, and invites other parties to put forward their build specs for publication. But while analysis like this may serve as useful guidance to inform design speci cations, it’s imperative that building designers start either commissioning building LCA consultants or using building LCA tools for themselves – and at the earliest possible stages in the design, in order to inform the speci cation – and focus the minds of suppliers to nd ways to reduce the embodied carbon of their solutions.
e ve timber frame variants posted the lowest embodied carbon scores, both in terms of the module A (cradle to practical completion) results, and the A-C (cradle-to-grave) results.
external cladding, such as charred timber cladding – which can o er the dual bene t of low upfront emissions and 100-year plus lifespans.
e low embodied carbon variant of ICF (wall type 11) comes in ninth at 9.9 tonnes, followed by the brickslip-clad externally insulated block variant (wall type 4) at 10 tonnes.
e extraordinarily high results for an admittedly unusually large solar PV roof in the case study on p69 are a case in point.
The low embodied carbon variant of ICF (wall type 11) comes in ninth at 9.9 tonnes, followed by the brickslip-clad externally insulated block variant (wall type 4) at 10 tonnes.
tonne of CO2e.
74 | passivehouseplus.ie | issue 41 ITFMA EMBODIED CARBON REPORT INSIGHT (above) Results, tonnes of C02e 11.46.26.23.54.24.44.24.66.68.07.9 -5.4-4.0-4.0-3.3-3.30.00.00.00.00.00.0 0.50.60.61.11.11.61.51.31.81.71.9 OmittedOmittedOmittedOmittedOmittedOmittedOmittedOmittedOmittedOmittedOmitted -0.5-0.5-0.50.00.00.0-1.0-0.9-0.2-1.0-0.4 0.90.90.00.00.11.00.40.00.00.40.0 OmittedOmittedOmittedOmittedOmittedOmittedOmittedOmittedOmittedOmittedOmitted 0.50.50.50.00.10.10.30.30.40.40.4 0.50.50.50.50.20.20.00.00.00.40.6 0.90.90.00.00.05.44.04.13.33.30.0 0.00.00.00.00.00.10.10.10.10.10.1 15.010.05.25.04.16.46.68.28.99.89.9 A1-A3 Manufacture A1-A3 Sequestered TransportA4 Siteto A5 Constuct B3B2,B1, B5B4, C1 Demolition C2 Transport C3/C4 (Recycled) C3/C4 (Incinerated) C3/C4 ll)(Landfi A-CTotalWall Types 5: Timber frame (I-beam, cellulose & renderboard) 7: Timber frame (mineral wool + PIR, renderboard) 9: Timber frame (PIR, renderboard) 6: Timber frame (PIR, renderboard) 8: Timber frame (PIR, block outer) 3: Block on flat (rendered EWI) 1: Cavity wall (rendered) 2: Cavity wall (brick clad) 11: ICF (20/25 RC, 70% GGBS, 0.4% rebar) 4: Block on flat (brick slip EWI) 10: ICF (28/35 RC, CEM I, 1% rebar)
the ICF or timber frame variants. e fairest comparison therefore is arguably between the rendered versions of all wall types, including systems with rendered block-clad outer leafs, rendered EWI, and renderboard systems.
Rendered cavity wall (wall type 1) comes in seventh at 8.9 tonnes, with brick-clad cavity wall (wall type 2) at 9.8 tonnes – reflecting the high embodied carbon of brick manufacturing.
Secondly, the ICF variants – and to a lesser extent the other concrete-based variants – are to a fairly large extent a ected by the assumptions around transport distance: 1.48 and 1.56 tonnes of CO2e are estimated for transporting concrete to site in the low embodied carbon and high embodied carbon ICF variants respectively, assuming 300 km by artic and 50 km by rigid trucks. While these distances may look less far-fetched given that the gures are based on round trips, over a tonne of CO2e is associated with the artic journeys speci cally. An ICF project near a cement manufacturer’s factory gate would stand to achieve signi cant reductions.It’salsoimportant not to take these results out of context, notwithstanding the fact that this article is focused on embodied carbon alone, and ignoring other considerations. External walls can represent a signi cant proportion of a building’s total embodied carbon, but there are other building elements which may have similar or greater impacts in some cases.
The second and third best results go to two timber frame walls with render board finishes, wall type 7 and 9, with the mineral wool/PIR insulated version (5.0 tonnes) scoring better than the PIR-only variant (5.2 tonnes). Wall type 6 – timber frame with mineral wool/PIR and blocker outer – comes in at 6.4 tonnes, while wall type 8, 8 – a PIR insulated timber frame wall with rendered block cladding – comes in at 6.6 tonnes. One point to note here: the timber frame variants 7-9 benefit significantly from the very low emissivity levels assumed for the foil-faced PIR insulation and foil-faced VCLs and membranes, where these materials were facing unventilated cavities, in line with ISO 6946:2017. This meant significantly reduced insulation thicknesses are required to achieve the 0.18 U-value backstop. The cavity wall variants also benefited from this emissivity – with the foil facing on the PIR facing into unventilated cavities.
timber frame variants posted the lowest embodied carbon scores, both in terms of the module A (cradle to practical completion) results, and the A-C (cradle-to-grave) results.
Sixth place and the best result for a concrete-based system goes to wall type 3, the block on at with EPS external insulation and silicone render, which at 8.2 tonnes adds over a tonne compared to the worst performing timber frame variant – and double the score of wall type
ere are a couple of important observations here. e rst is that the brick or brickslip clad variants fare signi cantly worse than their rendered equivalents. Note that brick or brick slip options were not considered for
carbon scores are expressed in terms of CO2 equivalent, or CO2e. This is a combined total of CO2 and other greenhouse gases converted into the equivalent amount of CO2
It’s also important not to take these results out of context, notwithstanding the fact that this article is focused on embodied carbon alone, and ignoring other considerations. External walls can represent a significant proportion of a building’s total embodied carbon, but there are other building elements which may have similar or greater impacts in some cases. The extraordinarily high results for an admittedly unusually large solar PV roof in the case study on p69 are a case in point.
All this talk of embodied carbon and building life cycle assessment (LCA) can be very daunting, but what does it mean? This is our stab at shedding some light, and explaining the jargon.
Shifting the focus from the emissions caused by energy used to heat, cool and power buildings, embodied carbon focuses instead on emissions generated in the construction of the building itself, from extraction of raw materials right through to the building’s eventual end of Embodiedlife.
Embodied carbon explained
Passive House Plus intends to add other build specs to this comparison in future issues, and invites other parties to put forward their build specs for publication. But while analysis like this may serve as useful guidance to inform design specifications, it’s imperative that building designers start either commissioning building LCA consultants or using building LCA tools for themselves – and at the earliest possible stages in the design, in order to inform the specification – and focus the minds of suppliers to find ways to reduce the embodied carbon of their solutions.
Carbon Assessment of Timber Frame Wall Types IRISH TIMBER FRAME MANUFACTURERS’ ASSOCIATION 15
The emissions totals are broken down into separate modules – A, B, C and D, which represent different stages of the building’s life. If buildings were living organisms, module A could be thought of as emissions released in gestation. Module B would be emissions released during the creature’s life, and module C would be emissions released when it dies. Module D makes this metaphor a little nightmarish, representing the potential benefits that may be salvaged by the proverbial gravedigging that is future recovery.
For the sake of transparency – and just to make a complicated process even more complicated – it is worth pointing out that module A includes two markedly different parts, and where possible we have tried to reflect this in the graphs we publish.
Module A (upfront emissions) includes emissions released up to the point of practical completion – including the manufacture of construction materials, transporting materials to site, and the construction process itself. Materials are covered by A1-A3, A4 covers transport to site, and A5 covers the construction process itself.
Module A (stored emissions) includes the CO2e sucked out of the atmosphere by building materials from biogenic sources – such as trees or other plants – and stored for the duration of their use in the building. They’re reported as a minus gure. Stored emissions should be reported separately in this way to discourage accountancy sleight of hand. There
There are a couple of important observations here. The first is that the brick or brickslip clad variants fare significantly worse than their rendered equivalents. Note that brick or brick slip options were not considered for the ICF or timber frame variants. The fairest comparison therefore is arguably between the rendered versions of all wall types, including systems with rendered block-clad outer leafs, rendered EWI, and renderboard systems.
The clear outlier from these 11 wall types is the higher embodied carbon variant of (wall type 10) bringing up the rear at 15 tonnes.
Secondly, the ICF variants – and to a lesser extent the other concretebased variants – are to a fairly large extent affected by the assumptions around transport distance: 1.48 and 1.56 tonnes of CO2e are estimated for transporting concrete to site in the low embodied carbon and high embodied carbon ICF variants respectively, assuming 300 km by artic and 50 km by rigid trucks. While these distances may look less farfetched given that the figures are based on round trips, over a tonne of CO2e is associated with the artic journeys specifically. An ICF project near a cement manufacturer’s factory gate would stand to achieve significant reductions.
The RIAI, RIBA and LETI all state that analysis should include a minimum of 95 per cent of cost, including substructure, superstructure, finishes, fixed FF&E, building services and associated refrigerant leakage.
Module C (end of life) estimates the amount of emissions released from the building when it is eventually taken down, taking account of demolition, transport, waste processing and disposal. At this point, the CO2e stored in building components is effectively regarded as being released into the atmosphere. In reality, it’s plausible that most of these emissions may not be released for a very long time, if at all, as the fabric of buildings can last for hundreds of years. (Though as high-profile building failures have shown, far shorter lifespans can occur due to defective materials, design or workmanship).
The Royal Institute of British Architects (RIBA) and the London Energy Transformation Initiative (LETI) in the UK, and the Royal Institute of the Architects of Ireland (RIAI), all exclude B6-B7 from their embodied carbon targets. (All three organisations have standalone operational energy targets, while RIBA and the RIAI also have water use targets.)
Building elements
In general, the embodied carbon calculations published in Passive House Plus endeavour to align with the requirements set out by RIBA or the RIAI, depending on whether the project is UK or Ireland-based, though typically external works are omitted. Where some (typically minor) elements have been omitted, we try to ensure this is stated in the description.
RIBA, RIAI or LETI targets, so we’re ignoring them too.
But where does a building begin and end, and what stuff should you count? Broadly speaking, the elements which can be included in an LCA are similar between the documents which frame the UK and EU approaches, respectively Table 3 in the RICS document, ‘Whole life carbon assessment for the built environment’, and Table 11 in Level(s) User manual 2 (Publication version 1.1).
Meanwhile LETI exclude the embodied carbon of renewable electricity generation, with the exception of building integrated systems.
It’s also critical to consider what is included within the scope of a building life cycle assessment, aside from taking account of whether modules A, B, C and D are included.
Carbon Assessment of Timber Frame Wall Types 16 IRISH TIMBER FRAME MANUFACTURERS’ ASSOCIATION
The RIAI targets follow the full Level(s) scope, but the RIBA and LETI targets exclude demolition and external works from the RICS scope.
Module B (use-phase emissions) looks ahead at the emissions predicted to be released during the building’s use period. B1 to B5 covers CO2e that may be released in the maintenance, repair and replacement of building components across the reference design life of the building, while B6 and B7 include emissions from estimated energy and water use respectively.
is new thinking that biogenic storage should be assessed dynamically, for instance to include sequestration from regrowth in a forest after timber is harvested. But for the sake of simplicity, we’ve chosen not to go there yet.
Readers would be advised to compare both documents, both of which include the whole building and external works, albeit with some elements described differently. One major dierence: RICS includes demolition and facilitation works – including specialist groundworks, which can contribute quite considerably to embodied carbon in some cases, such as excavating and transporting muck. As it stands Level(s) does not include these elements, but member states are free to include elements outside of the scope of Level(s) – and report on them separately, or to include totals with and without these elements.
The length of the projected building lifespan can have a significant impact here. RICS (Royal Institution of Chartered Surveyors) species a 60-year lifespan – although there are plans to start adjusting totals based on building type – while the EU Level(s) framework sets the design life at 50 years, which may mean inclusion of fewer replacements of components. RIBA and LETI use the RICS 60-year gure, while the RIAI in Ireland use the EU 50-year gure.
Module D (recycling potential) covers the net environmental benefits or loads that may result from reuse, recycling and energy recovery –including the potential reuse or recycling of building components, while potential energy exported into the grid during the building’s life is also crowbarred in here. Module D emissions aren’t included in the
RIBA and the RIAI’s 2030 Climate Challenge targets set embodied carbon targets for buildings, including a target by 2030 of 750 kg CO2e/ m2 (gross internal area) for offices, 540 for schools and 625 for domestic buildings. The RIAI sets a higher target of 450 for dwellings above 133m2 or for low density homes of up to two storeys. RIBA and the RIAI require building LCAs to include A1-A5, B1-B5 and C1-C4, and do not include module D. LETI also includes a module A target, to focus attention on the upfront emissions.
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