Retrofit calculations

Retrofit calculations ensure accurate energy savings and carbon emissions projections when planning future retrofits. These calculations use the resource consumption data provided by customers to model the impact of retrofit measures, updating the energy and carbon performance of the building portfolio.

How retrofit calculations work

When a retrofit is planned for a building, a projection of future energy consumption and carbon emissions is calculated based on the expected impact of the planned retrofit on the latest recorded energy consumption and emissions data. The new resource and emission values replace the old ones, starting from the environmental impact year of the scheduled retrofit.

Depending on the type of retrofit:

• The latest recorded resource consumption is used, either from operational measurements or projections from a prior scheduled retrofit.

• A new emission factor is applied for carbon emission simulations.

• Percentage reductions in heating or electricity demand entered by the user are incorporated into the calculation.

Retrofitting a building can minimize its environmental impact through energy-saving measures or by changing its energy source to one with lower emissions per consumption. Our retrofit calculations support both approaches to building energy performance improvement, with specific considerations outlined below.

Energy-saving measures

Some retrofit measures require multiple years for full implementation, while others can be achieved within a single year. Our calculations support both cases, with the measure’s impact on the building’s resource and emission values beginning in the environmental impact year selected by the user.

If multiple retrofit measures have the same environmental impact year, the combined impact of these measures is calculated using:

The formula for combined savings: For four retrofits with the same environmental impact start year and expected savings (expressed as fractions) R1, R2, R3, R4:

Rc = 1 - (1 - R1) * (1 - R2) * (1 - R3) * (1 - R4)

This formula accounts for the changing baseline with each successive measure.

Change in energy source

Our calculations assume that a change in energy source happens within one year and does not support multi-year periods. Additionally, only one change can be planned for a specific energy source in a given year. The environmental impact of the change begins in the same year as the retrofit.

Example: If a building’s heating energy source is planned to switch from oil-based fuels to natural gas in 2026, an additional change in the heating source (e.g., from natural gas to district heating) cannot be scheduled in the same year.

Example: Multiple energy-saving retrofits with the same environmental impact year

A building undergoes multiple energy retrofits over different years to enhance efficiency, including:

• Installing a new gas boiler (2025-2027).

• Improving the thermal envelope (2025-2027).

• Optimizing the HVAC system (2026-2027).

The cumulative impact of these retrofits results in significant energy reductions:

• Heating savings: Initial demand of 70 kWh/sqm per year is reduced step by step through 20% savings from the gas boiler, 30% from thermal envelope improvements, and 10% from HVAC optimization. The final heating demand becomes 35.28 kWh/sqm per year.

• Electricity savings: Initial consumption of 30 kWh/sqm per year is reduced by 10% due to HVAC optimization, resulting in 27 kWh/sqm per year.

Steps to calculate Retrofit impact

• Determine baseline consumption:

  Identify the building’s current heating and electricity consumption.

• Apply savings sequentially: Instead of simply adding percentage savings, apply each reduction iteratively:

  • Heating: 70 × [1 − (1 − 0.20) × (1 − 0.30) × (1 − 0.10)]

  • Electricity: 30 × [1 − (1 − 0.10)]

• Evaluate final energy consumption: The final heating demand is 35.28 kWh/sqm per year, and electricity consumption is 27 kWh/sqm per year.

Example: Upgrading to district heating

A building in Germany plans to upgrade its heating system from oil-based to district heating in 2025 while enhancing facade insulation from 2025 to 2026 (with environmental impact starting in 2026). The retrofit results in:

• Reduction in carbon emissions by switching to district heating.

• 25% decrease in heating demand due to improved insulation.

Steps to perform retrofit calculations:

• Utilize the latest heating consumption data for accurate baseline calculations.

• Apply relevant emission factors: From 2025 onward, use the district heating emission factor for Germany.

• Incorporate insulation improvements: In 2026, apply a 25% reduction in heating demand due to facade insulation.

• Review the results in the Retrofit view preview, which provides insights into projected carbon emission reductions and energy savings.

These steps allow users to evaluate the benefits of upgrading a building’s heating system and insulation, enabling data-driven decisions for a more sustainable future.

Change heating source: Heat pump

Heat pumps are highly efficient systems that transfer heat from external sources (air, ground, or water) to buildings. They consume significantly less electricity than traditional heating systems, making them a sustainable retrofit choice.

Steps to switch to a heat pump:

• Use the last recorded heating consumption value (from operational measurement or the latest retrofit calculation).

• Divide heating consumption by the Coefficient of Performance (COP) (Default COP: 3).

• The resulting value represents the electricity consumption required for heating.

• The BuildingMinds platform applies the appropriate emission factor based on the electricity subtype:

  • Grid electricity (normal contract)

  • Grid electricity (green contract)

  • Self-generated electricity