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Buildings

1. Context

The carbon footprint considered in the Buildings module includes the impact associated with the following two sub-modules:

  • The Rooms sub-module covers emissions relating to heating, cooling, ventilation and lighting of the various building locations used by the unit.
  • The Energy Combustion Emissions sub-module is available to account for other energy combustion emissions in cases where a unit uses a non-centralised energy source. Emissions related to energy combustion in laboratories stem mainly from the on-site combustion of fuels used for heating, ventilation, hot water and specialized equipment.

The Buildings module aims to capture these energy-related emissions. The Rooms sub-module covers mainly indirect emissions related to electricity and therefore Scope 2. The Energy Combustion Emissions sub-module covers direct emissions and therefore Scope 1.

2. Data collected

2.1 CO₂ Calculator workspace

  • Rooms sub-module: For this sub-module, the internal database on floor location provides a list of the rooms used by a unit and their surfaces. Hypotheses on energy consumption (kWh/m²) vary by building and room type. These estimates are created using information provided by the Vice-Presidency for Operations at EPFL (VPO), including the campus's total energy consumption, the total energy consumption of specific buildings, and the detailed technical inventories of certain buildings, which are then used to extrapolate hypotheses for others.

  • Energy Combustion Emissions sub-module: Data on centralised thermal energy consumption for the ‘Energy Combustion Emissions’ sub-module is entered manually.

2.2 CO₂ Project planner workspace

Grant proposal

Data related to building use must be entered manually to estimate the project's carbon footprint as part of the grant proposal. For principal users, data from the Rooms sub-module are automatically imported from the CO₂ Calculator.

Detailed per year

For principal users, data from the Rooms sub-module are automatically imported from the CO₂ Calculator. They can then define, for each year, a reference percentage to estimate the share of facilities-related emissions attributable to the project. Data related to energy combustion emissions must be entered manually unless principal users have already entered these data in the CO₂ Calculator. For standard users, data from the CO₂ Calculator are not imported, and information for both sub-modules must therefore be entered manually.

2.3 CO₂ Explorer workspace

To explore the carbon footprint of the Buildings module, users can manually enter data related to facility use or energy combustion emissions.

3. Emission factors

Rooms sub-module

For electricity, the emission factor 0.097 kg CO₂-eq/kWh (BAFU, 2025) is used in this module.

Energy Combustion Emissions sub-module

For centralised thermal energy consumption, the emission factors are taken from the Corporate Footprint Calculator, and in particular from the BAFU database (2025).

For energy combustion emissions from non-centralised systems, the emission factors from Labos1point5 (2021, 2022) are used (see Section 7, Appendix).

4. Methodology

Rooms sub-module

The carbon footprint of each room \(CF_{rooms}\) is calculated as the product of the room’s floor location in m² and the consumption of heating, cooling, ventilation and lighting in kWh per m² by room type and by building as well as the emission factor for Swiss electricity as follows:

\[ CF_{rooms} = Surface \cdot \left( \left( Cons_{heating, building, room_{type}} \cdot conversion_{factor} \right)+ Cons_{cooling, building, room_{type}} + Cons_{ventilation, building, room_{type}} + Cons_{lighting, building, room_{type}} \right) \cdot EF_{electricity} \]

Where:

  • \(buildings\): the building in which the unit’s rooms are located
  • \(room_{type}\): type from the categories office, miscellaneous, laboratories, archives, libraries and auditoriums
  • \(Surface\): floor occupation in m²
  • \(Cons_{heating, building, room_{type}}\)
  • \(Cons_{cooling, building, room_{type}}\)
  • \(Cons_{ventilation, building, room_{type}}\)
  • \(Cons_{lighting, building, room_{type}}\): electricity consumption for heating, cooling, ventilation and lighting of the room in kWh/m² extrapolated from VPO data, depending on the buildings and room type
  • \(conversion_factor\): this is a specific conversion factor that is used when the building's heating is thermal rather than electric.
  • \(EF_{electricity}\): emission factor for electricity consumption (0.097 kg CO₂-eq/kWh (BAFU, 2025))

Energy Combustion Emissions sub-module

\(CF_{combustion}\) carbon footprint is calculated as the product of the amount of fuel consumed in kg or kWh and the corresponding emission factor, as follows:

\[ CF_{combustion} = Q_{fuel_{type}} \cdot EF_{fuel_{type}} \]

Where:

  • \(fuel_{type}\): type of fuel used: natural gas, domestic fuel oil, biomethane, wood pellets, wood chips and logs
  • \(Q_{{fuel}_{type}}\): amount of fuel used for a non-centralised heating source in kg or kWh, entered manually.
  • \(EF_{{fuel}_{type}}\): emission factor for each fuel in kg CO₂-eq/kWh or kg CO₂-eq/kg.

In the CO₂ Project planner, under the Detailed per year section, principal users can define, for each year, a reference percentage to estimate the share of emissions from the Rooms and Energy Combustion Emissions sub-modules that is attributable to the project.

The carbon footprint associated with the Rooms and Energy Combustion Emissions sub-modules within the project is calculated by applying this reference percentage to the corresponding emissions (in kg CO₂-eq) for each room or energy combustion source.

5. Limitations

  • The floor location in m² provided by the internal database on rooms may not reflect reality in cases where rooms are shared or loaned.
  • Electricity consumption for heating, cooling, ventilation and lighting of the rooms is extrapolated from a total consumption value per building provided by the VPO. This is combined with the specific technical inventories for certain buildings to derive a value for each use (heating, cooling, ventilation and lighting) and for each room type (office, miscellaneous, laboratory, archive, library or auditorium).
  • The emission factor of 0.097 kg CO₂-eq/kWh represents a Swiss annual average, not the electricity mix at the time the equipment is in use.
  • Fuel consumption for estimating energy combustion emissions from a non-centralised heating system must be entered manually. The quality of the results therefore depends on the quality of this input data.

6. References

7. Appendix

Energy combustion emission category Unit Name Year Emission factor Unit of the emission factor
Natural gas kWh (net calorific value) Natural gas, average mix 2022 0.24 kg CO₂-eq / kWh PCI
Heating oil kWh PCI Heating oil 2014 0.3243 kg CO₂-eq / kWh PCI
Biomethan kWh PCI Biomethane – Injected into the networks – Average mix 2020 0.0444 kg CO₂-eq / kWh PCI
Wood pellets kg Wood pellets – 8% of humidity 2014 0.1108 kg CO₂-eq / kg
Forest chips kg Forest chips – 25% of humidity 2022 0.0503 kg CO₂-eq / kg
Wood logs kg Wood logs – 20% of humidity 2014 0.1138 kg CO₂-eq / kg 
Table 2 : Energy combustion emissions from non-centralised systems (Labos 1point5, 2021, 2022)