One of the key challenges in building decarbonization is not just identifying what interventions to implement, but determining when to implement them. Retrofit decisions rarely happen all at once; they are shaped by tenant lease lengths and turnover, capital planning cycles, equipment lifespans, and regulatory timelines. The Decarbonization Over Time feature in Carbon Signal allows you to create realistic, phased implementation plans that reflect these real-world constraints.
Decarbonization Over Time takes the results of the baseline building and applies selected interventions across a multi-year timeline. The result is a dynamic emissions reduction forecast that can be used for capital budgeting, investment planning, and communicating long-term decarbonization goals. Rather than a single static intervention package, this feature supports iterative planning.
Creating a Reduction Pathway
New interventions default to an implementation year of 2025, and they are not placed on the pathway automatically. Until the autosequencer selects an intervention, or you switch on Add to pathway for it yourself, nothing is scheduled.
To modify when an intervention is implemented, navigate to the Interventions table listing each intervention along with its estimated emissions reduction, implementation year, and capex cost. Click the row for the intervention you want to update. There is no edit icon; clicking anywhere on the row opens a drawer on the right.
The drawer holds an Intervention timeline section where you can switch on Add to pathway and change the Implementation Year. This must be a year between 2020 and 2049.
After making your selection, click Save. The Reduction Pathway chart will then refresh automatically to reflect the change, showing the updated carbon reduction occurring in the selected year. This allows you to quickly adjust your timeline and see how different intervention schedules affect your overall emissions trajectory.
Using Time-Based Emission Factors
The Time-Based Emission Factors feature can be enabled to reflect how energy-related emissions are expected to change over time. A good example of this is that electricity grid emissions are expected to decrease over time as the mix of energy sources on the grid becomes cleaner. This allows you to understand how your building’s carbon emissions change with evolving grid carbon intensity, even if energy use remains constant.
To access this feature, go to the Building Details page and click the Emission factors tab.
By default, Carbon Signal selects the most location-specific dataset available for the building, preferring NREL Cambium, then CRREM, then Our World In Data. OWID is the worldwide fallback, used when no more specific dataset covers the building’s location, so most buildings in the United States default to NREL Cambium rather than OWID.
To review or update emissions factors:
- Open the Emission factors tab and click Edit.
- Each available dataset is shown as its own block, listing factors for all four utility types: Electricity, Natural Gas, District Heating, and District Cooling.
- Select the radio button on the dataset you want to use. The choice applies to all four utilities at once, so sources cannot be mixed per utility. The datasets are:
- Our World In Data (OWID)
- NREL Cambium
- Carbon Risk Real Estate Monitor (CRREM)
- Custom
You can also set custom emissions factors by clicking on the value you’d like to edit for a specific year. Custom values can be entered in 5-year increments between 2020 and 2050. You are not required to enter values for every 5-year interval. If you enter a value for only some years, the platform will interpolate the emissions factors for the years in between.
This flexibility allows you to tailor emissions trajectories based on your own assumptions or internal forecasts.
CRREM Targets
The Carbon Risk Real Estate Monitor (CRREM) provides science-based decarbonization targets for real estate, aligned with the goals of the Paris Agreement. These targets help assess whether a building’s projected emissions are on track with a 1.5°C carbon reduction pathway.
CRREM is now offered as one of Carbon Signal’s performance standards, which replaced the earlier science-based targets feature. The Reduction Pathway chart on the Building Details page does not draw a target line by default: its second dropdown starts on No target. Select CRREM, or any other applicable performance standard, from that dropdown to overlay it as a reference line.
The standards offered in the dropdown are determined by the building’s type and location.
If CRREM does not appear in the list for your building, this means CRREM does not currently provide a target for that specific location and building type combination. For more on how standards are set up and applied, see the Building Performance Standards page.
Capital Expenditures (CapEx) Planning
In addition to tracking emissions reductions, the Decarbonization Over Time feature is designed to support capital planning by visualizing the estimated capital expenditures (CapEx) of interventions over time. A Cash flow chart above the Interventions table plots the intervention capex costs against the operational savings they produce, year by year, alongside the net present value and marginal abatement cost for the plan. This helps users align retrofit planning with annual budget cycles and investment timelines.
The chart can be switched between Net and Cumulative views, the latter providing a clear picture of total spending and savings over the planning horizon.
Understanding the Interaction Between Building Interventions
It’s easy to assume that if one intervention saves energy, and another does too, you can just add the two together. But buildings don’t work that way. When you make one change—like improving insulation—it can affect how much of a difference another change—like replacing the heating system—will make. Since better insulation means the building needs less heat, the new heating system won’t save as much as it would have on its own. These overlapping effects mean that doing multiple upgrades doesn’t always equal the total of their individual savings.
Carbon Signal takes this into account in the Decarbonization Over Time tool. It applies each intervention one after the other and updates the impact along the way. That way, the savings shown are more accurate and avoid counting the same benefits twice.