Guidance for using LCA for LEED v4 MRc1 Building Life-Cycle Impact Reduction, Option 4
Life cycle assessment for LEED v4 MRc1 Building Life-cycle Impact reduction credit and its option 4: Whole building impact assessment.
This guidance applies for following for One Click LCA tools:
LCA for LEED (CML)
LCA for LEED, International (using CML impact assessment methodology)
LCA for LEED, US (using TRACI impact assessment methodology)
LCA for LEED, Canada (using TRACI impact assessment methodology)
This guidance is planned to be used along with the credit reporting template. Find at the bottom of the page the attachments of our ready reports that you can download and fill to be submitted for LEED LCA credits and check out our example report
One Click LCA reporting template for LEED v4 Mrc1 – CML (Europe, rest of the World)
One Click LCA reporting template for LEED v4 Mrc1 – TRACI (US, Canada)
One Click LCA for LEED v4 Example report
The MRc1 credit option 4 is suitable for new construction (buildings or portions of buildings).
The idea of the credit is to conduct a life-cycle assessment of the project’s structure and enclosure to show a minimum of 10% reduction in building material life cycle impacts compared to a baseline in at least 3 different impact categories. One of the categories with minimum 10 % reduction must be Global warming potential. No impact category assessed as part of the life-cycle assessment may increase by more than 5% compared with the baseline building. If the design team can show improvement in all of the 6 categories they will get an additional exemplary credit.
LEED impact categories and units
In life cycle assessment projects, the potential to cause environmental harm is assessed over its whole life time (1) for specified environmental impacts.
In LEED the life cycle assessment is done for six different environmental impact categories. Each impact category describes a particular category of environmental impacts. The impacts are expressed as quantities of a matter that has the potential to cause such impacts – but they do not represent the actual harm (final impact, e.g. endpoint) eventually caused. For instance, global warming potential represents the amount of CO2e gases released. But the final impact is the acceleration to the polar melt, for example.
The LCA impact categories for LEED LCA and their descriptions:
Global Warming Potential describes how much a product contributes to climate change. When LCA concerns only this impact category, it’s called the carbon footprint
Acidification describes how much product acidifies the environment, resulting e.g. in acid rain
Eutrophication describes flow of nutrients to ecosystems, resulting e.g. in algae growth
Ozone Depletion describes damage caused to the Ozone Layer in the stratosphere
Tropospheric Ozone describes the quantity of summer smog causing gases emitted
Depletion of non-renewable energy resources describes how much fossil resources are withdrawn
In the calculations all the different emissions from evaluated life cycle stages are collected and normalised to a common unit. In case of Global warming potential the reference is the warming potential (radiative forcing) of CO2 emissions e.g. how much heat 1 kg of CO2 will tie into the atmosphere. The warming potential of all the other cases is compared to the CO2 and based on that the quantities are normalised to the common unit. For instance, the warming potential of methane is 24 times higher than the one of CO2 1 kg methane emissions will be 24 kg CO2equivalents. Impact assessment methodology defines the relative weight of different emissions and the normalisation unit. In LEED v4 CML, TRACI and ReCiPe methodologies are accepted. Out of these methods TRACI is commonly used in North America and CML is required by the EN standard and is therefore is de facto the required methodology in Europe and also widely used internationally.
LCA impact indicator units
TRACI 2.1
CML 2002
ReCiPe
Global warming potential (greenhouse gases)
CO2e
CO2e
CO2e
Depletion of the stratospheric ozone layer
CFC-11-eq
CFC-11-eq
CFC-11-eq
Acidification of land and water sources
SO2e
SO2e
SO2e
Eutrophication
N eq
PO43e
P eq
Formation of tropospheric ozone (photochemical oxidant formation)
One Click LCA supports both TRACI 2.1 and CML (2002 – November 2012 or newer). LEED tools for US and Canada support TRACI 2.1 methodology and the versions for Europe and international users CML (2002 – November 2012 or newer). In One Click LCA all of the datasets follow ISO14044 standards and thus, the data is automatically compliant with the required standards and required impact assessment methodology.
(1) Building service life for LEED is estimated to be 60 years for all of the building types, in One Click LCA this is applied automatically in the calculations.
Building material scope
The material scope required for LEED is specified in the following table. Some of the materials may be included but adding them will not provide any extra credit.
Element
Included
Comment (mark if something is not relevant)
Standard foundations
Yes
Special foundations
Yes
Slab on Grade
Yes
Basement excavation
No
Basement Walls
Yes
Columns
Yes
Beams
Yes
Floor Construction
Yes
Floor / Ceiling Finishes
?
Optional
Roof Construction
Yes
Exterior and Semi-exterior Walls from cladding to finishing
Yes
Semi-exterior elements separate conditioned space from unconditioned space or that encloses semi-heated space (e.g., attic, crawl space, and basement)
Exterior Windows
Yes
Exterior Doors
Yes
Roof Coverings
Yes
Roof Openings
Yes
Load-Bearing partitions
Yes
Other Partitions
?
Optional
Interior Doors
?
Optional
Fittings
No
Stair Construction
Yes
Stair Finishes
?
Optional
Wall finishes
Yes
For included walls only
Parking structures
Yes
Parking lots
No
As per LEED v4 specification the following elements were excluded from the analysis: electrical and mechanical equipment and controls, plumbing fixtures, fire detection and alarm system fixtures, elevators, and conveying systems, excavation and other site development, and parking lots.
Basic calculation process for LEED LCA in One Click LCA
Create a new design
Fill in the construction materials input form of the design either manually or by import.
Add all of the materials required by the calculation scope (see above) by choosing them suitable environmental profiles.
You are allowed to use either average data, manufacturer specific EPDs (recommended) or similar products from another manufacturer. Use net quantities (amounts of material installed in the building); the on-site losses of materials would be included in module A5 but that is excluded from the calculation by credit specification.
This information will be used to calculate the raw material harvesting, transportation and manufacturing impacts in A1-A3.
Once the correct materials and quantities are provided, set the transportation distances from material manufacturer to the project site and transport methods, or choose the most suitable set of default transport distances.
The average transportation distances can be set on from the project main page. If they are chosen any material will use the average distance unless a more specific one is given in the questionnaire. This information will be used to calculate the impacts from material transportation in A4.
Finally, check the material service life.
This information will be used to calculate the material replacements for B1-B5.
Material service life means how long each material will last in your building. If the service life is less than 60 years the material will have to be replaced. From environmental impacts point of view this means additional emissions from production of new material that is needed to replace the old one.
Each of the material in One Click LCA database has a default service life. However, as the exposure conditions of the materials may vary, it may be good to check that the service life matches to your buildings conditions. Especially it is good to check the external wall and roof material service lives as the weather conditions may vary greatly between areas.
Fill in the building area in the respective input form. This information will be used as a divider for the results in a separate result row and it will help you to understand how the results compare to other projects. Gross floor area is required.
Fill the project area in the local conditions input form (optional, only applies for areas with little or no local data available). This information will be used to compensate any material data chosen from other area to match projects local material manufacturing conditions. You will only have to fill in the project area and the calculation results will be compensated automatically.
Next steps:
After you have done one calculation you can create as many additional designs you wish either by copying the first one or by creating a new empty one. This can be used for creating a baseline or to create additional “what if” scenarios. To copy a design click its name and choose ”Copy”. To create a new one press “+Add a design” button on the project main page.
Once the Baseline design is completed, create a copy of it and name it 'Proposed design'.
Requirements for the baseline
To make sure that the baseline and proposed models can be accurately compared following aspects must be kept the same in both baseline and proposed building:
LCA scope requirements. The functional unit and system boundary must be identical for the baseline and proposed buildings. Basically this means that you’ll have to use the same calculation tool for both.
Size. The gross floor area of the baseline and proposed buildings must be the same. The two designs can have different massing, provided the gross area is the same.
Function. The baseline and proposed buildings must serve the same programmatic function. If the project is a mixed-use residential building with retail in the first floor, the baseline building must have the same program, but the elements can be in different locations in the building. If the project is a hospital with stringent air quality and humidity control, both the baseline and the proposed cases must meet those functional requirements.
Orientation. The orientation—the directional exposure—of the baseline and proposed buildings must be the same, but the shape may differ. Orientation must be the same because exposure to the sun affects solar heat gain within the building and will skew LCA results for energy performance.
Location. Both the baseline and the proposed buildings must be located in the same ASHRAE 90.1–2010 climate zone and assumed to be on the same site.
Operating energy performance. The baseline and proposed buildings must meet EA Prerequisite Minimum Energy Performance by adhering to the requirements of ASHRAE 90.1–2010, Appendix G, Opaque Assemblies, Vertical Fenestration, Skylights, and Roof Solar Reflectance and Thermal Emittance sections, because comparing an energy-efficient proposed building with an underperforming baseline building will skew the results. Increasing wall mass or insulation unnecessarily in the baseline building to show dematerialization in the proposed building is not acceptable. Energy modeling for either building is not required for this credit.
Other portions of the baseline building may be modified from the basic ASHRAE 90.1 requirements to capture the LCA goals of the project team.
As a summary:
You are allowed to
You are not allowed to
Optimize and reduce the mass of your actual building (from any studied part of the building)
Increase wall mass or insulation unnecessarily for the baseline building to show dematerialization
Change the structures and design of the building, including stud spacing, floor-to-ceiling heights, changes in the use of beams and pillars
Use a different area for the baseline building and actual design (specified as gross area)
Identify opportunities to make design changes to use lower -emissions materials or specify the use of specific products with quantified life-cycle impacts
Omit required parts of the envelope and structure: footings and foundations, structural wall assembly (from cladding to interior finishes), structural floors and ceilings (not including finishes), roof assemblies
Include additional elements, such as interior nonstructural walls or finishes (no extra credit)
Include excavation, site development, parking lots or building technologies and systems
Strategies for creating the baseline in One Click LCA
Option 1, creating variants and the baseline based on current proposed building analysis:
For many of the project cases this is the most efficient strategy. In this strategy you will first calculate the life cycle assessment of the current proposed building design and then use that one to study alternative material / structural options which may or may not lead to changing the proposed building. Finally, the baseline can be can be one of the created alternatives. The benefits of this strategy is that as the baseline is based on the proposed building design you’ll be easily able to ensure the equivalency in floor area, location, function, energy performance, and directional exposure. When testing different material / structural choices you’ll just have to ensure that:
All alternative enclosure roof, wall and slab materials were modelled with similar R-value / U-value / F-Factor to ensure similar energy loss through the structure
The size and location of the windows and skylights were kept similar in both models to ensure similar energy loss through the structure
Structural elements were modelled with required load bearing capacity
One Click LCA enables you to make the alternative studies easily in the web interface.
Steps to complete the analysis:
Create a copy of your existing design by clicking its name and choosing ”Copy”. You can also rename a design from the same select.
Open the created design’s construction materials query to study “what if” scenario analyses and support design decisions to evaluate and select environmentally preferable assemblies and materials. A good way to start is to check your existing design’s report to find out what causes a lot of emissions and to check if there are any more sustainable alternatives available. Examples of alternatives analyses could include the following:
Choosing different types of materials (e.g. brick wall vs. concrete wall)
Evaluating different structural system types, such as load-bearing walls versus columns
Choosing products with different kind of service lives
Choosing products from different manufacturers
Optimizing structural system design (e.g. column spacing, slab depth)
Save the final proposed design.
Open the Results page of the proposed design. Click the Compare button and select as the point of comparison the earlier building design. The percentage differences will appear to the table. You can create several different alternatives to find out options and to define the baseline.
Option 2, using early stage or alternative design model as a baseline:
If you are able to start the process early in the design process or you have available information about some design options that were studied earlier you may use these as a baseline. In this case you’ll need to calculate an LCA based on the information of the early stage / alternative design. The benefits of the early model is that you may have a change to suggest significant changes to the building design to improve it. In both alternative and early stage model you’ll also have the baseline information already available from your project so you do not have to figure out which kind of alternatives could be suitable. However, if the project design has changed a lot on the way you’ll have to pay some attention on checking the equivalence and may need to change the baseline to match the final design to ensure comparability. When creating your baseline / proposed building you’ll have to ensure that:
Both proposed and baseline building have same floor area and directional exposure
All alternative enclosure roof, wall and slab materials were modelled with similar R-value / U-value / F-Factor to ensure similar energy loss through the structure
The size and location of the windows and skylights were kept similar in both models to ensure similar energy loss through the structure
Structural elements were modelled with required load bearing capacity
Steps to complete the analysis:
Please note that this applies to a case where you start in early stage with current model or have the design data for alternative design easily available as BIM or excel export. In other cases we recommend still creating the baseline based on proposed building but using the material choices from the alternative or early design option for it.
Create a new design and name it 'Baseline'.
Fill in the information based on the design and study results. If you already have calculated the proposed building you can compare the results by pressing 'Compare Designs' button in the result report page.
Optional: Create a copy of this design to study results by clicking the name and choosing 'Copy'. Open the created design’s construction materials query to study “what if” scenario analyses and support design decisions to evaluate and select environmentally preferable assemblies and materials. A good way to start is to check your existing design’s report to find out what causes a lot of emissions and to check if there are any more sustainable alternatives available.
Option 3, using archetype design:
If either of the previous options does not work for you it is also possible to create an archetype building with typical local structures for the baseline. This might be the easier way if you are planning to change the whole structural system of the project. Also in this case the easiest way is to use the geometry of the existing project to ensure the equivalence though you are allowed to choose the geometry too in case you the floor area, directional exposure and directions of windows remain the same. When creating your baseline / proposed building you’ll have to ensure that:
They serve the same function and have the same location which for instance defines the needed foundation structures
Both proposed and baseline building have same floor area and directional exposure
All alternative enclosure roof, wall and slab materials were modelled with similar R-value / U-value / F-Factor to ensure similar energy loss through the structure
The size and location of the windows and skylights were kept similar in both models to ensure similar energy loss through the structure
Structural elements were modelled with required load bearing capacity
The easiest way to do this is to use the average constructions from the database but also defining the constructions you wish to use in our Excel template might be an efficient way. The recommended workflow is as follows:
Define the geometry for the baseline project, basically this means the areas for the included constructions such as external walls or roofs. If you do not the same geometry with the proposed building ensure the same directional exposure and similar location of windows etc.
Use those areas to fill in the construction to our excel template or directly to the software using ready-made default constructions. Ensure that the insulation level and resulting heat loss are equivalent and ensure you use the same requirements for load bearing capacity. Make sure you’ll add all the necessary building elements.
Compare your results with the proposed design.
Once you have achieved the desired credits fill in our reporting template to write the report (attached to the guide).
Video guide for carbon reduction
Create further changes until you reach your goal for the credit. Check our tips for reducing carbon and other environmental impacts
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