How does TESSA calculate embodied carbon metrics?

TESSA automatically generates Embodied Carbon numbers by extracting measurements from the Design Options and applying these to the embodied carbon factors in the database produced and maintained by Modulous. Global Warming Potential values have been extracted from the respective Environmental Product Declarations (EPDs) of the materials provided by manufacturer’s databases. If EPDs are not available for the specified materials, a generic value closest to that material specification is determined from publicly available databases. 

The embodied carbon numbers follow RICS reporting format, where the information includes the sum of basebuild and modular elements. TESSA provides carbon certainty for 30% to 40% of the overall construction build-up (the modular elements) and bench marked carbon estimates for the base build at feasibility stage. 

Measurement Unit

Results are presented in terms of Global Warming Potential over a 100 years and the units are kg of CO₂ equivalent (kgCO₂e, or kg in the International Unit System).

Definition & Scope

Whole life carbon (WLC) assessment 

A WLC is an assessment of the sum of all building-related emissions over a building's entire life (refer to figure below). The metric for assessing the emissions or climate change impacts of greenhouse gas emissions is Global Warming Potential (GWP). This is expressed in units of CO2 equivalent (CO2e) over 100 years, commonly referred to as ‘carbon emissions’.

The Reference study period used in the carbon assessments, based on the principles outlined in EN 15978:2011 is 60 years (domestic projects).

Environmental Product Declarations (EPD)

An independently verified and registered document that communicates transparent and comparable information about the life cycle environmental impact of a product.

The current version of TESSA supports quantifying carbon emissions from A1-A3, also known as the Product Stage or ‘Cradle to Gate’ emissions in a Life Cycle Assessment. We are planning to extend our assessment to A1-A5, or 'cradle to practical completion`, in the next release of TESSA, and provide a cradle to cradle assessment in 2024.   

The substructure is currently unavailable in TESSA. We are developing ways to accurately measure carbon footprint of the substructure and will be included within the next version of the software.

Whole Life Carbon: EN 15978:2011 The different stages of the building assessment

Methodology

The quantity of each material is an estimate derived from cost data to which respective carbon factors are assigned. Carbon factor represents the measure of the Global Warming Potential (GWP) of the respective materials. These values are extracted from Environmental Product Declarations (EPDs) closest in specification to the material being used. As this is a straightforward calculation, the embodied carbon for an entire building can be estimated quickly even at concept stage, allowing design options to be compared quantitatively.

LCA calculation process (Reference: RICS)

For example:
Carbon intensity of steel (at 60% recycled content): 2.12 kgCO₂/kg
Embodied carbon of 100 kg of steel: 100 x 2.12 = 212 kgCO₂e  

Could you add something around the 60% recycled content, what it means, what we currently achieved, what's our target and the sensitivity of the result to this parameter.

Assumptions & Clarifications

All assumptions for embodied carbon calculations align with the cost assumptions & clarifications except the following instances:

1 Substructure

Currently unavailable in this version of TESSA. We are developing ways to accurately measure carbon footprint of the substructure and will be included within the next version of the software.

2 Superstructure

2.3 Roof

Base Build

• Roof Finish – Photovoltaic panels provisionally included to cover roof area to 25% 

2.4 Stairs

Base Build

• Slip resistant vinyl flooring finish with nosings

2.5 External Walls

Base Build

• Single skin blockwork walls to service locations including forming openings and penetrations. External wall finish above fixed to single skin blockwork for facade where applicable.  
• Includes all associated detailing and finishing costs for penetrations, openings, articulations and abutments in the external wall 
• Entrance enhancement allowance for canopies and features to main building entrance 
• External/entrance signage allowance

Modular

• Includes all associated detailing and finishing costs for penetrations, openings, articulations and abutments in the Modulous external wall system 

2.7 Internal Walls & Partitions

Base Build

• Single skin lightweight blockwork walls to service locations including forming openings and penetrations

3 Internal Finishes

3.3 Ceiling Finishes

Base Build

• Allowance for access hatches/panels

Modular

• Allowance for access hatches/panels 

4 Fittings, Furnishings and Equipment 

4.1 Fittings & Furnishings

Base Build

• Residential Letter Boxes
• Interior Wayfinding Signage