Project Overview
For my final project, I want to develop DecarbFit, a parametric design assistant that helps designers evaluate low-carbon building envelope strategies during the earliest stages of design. The tool is inspired by my broader interest in building decarbonization and serves as a simplified prototype of a larger concept focused on carbon-informed design decision-making.
The building envelope is one of the most influential components affecting both embodied carbon and operational performance. Decisions regarding wall systems, insulation levels, glazing ratios, and façade configurations are often made during schematic design when there is limited information available. However, these early decisions can significantly impact a building's lifetime carbon footprint and construction cost.
DecarbFit addresses this challenge by providing immediate feedback on the carbon, cost, and energy implications of different envelope strategies. Rather than requiring a detailed energy model or life cycle assessment, the tool uses simplified calculations and assumptions to help users compare alternatives quickly and identify more balanced design solutions.
Intended Users
DecarbFit is intended for several types of users involved in sustainable building design.
Architects can use the tool during conceptual and schematic design to understand how envelope decisions influence carbon and cost before the building geometry becomes fixed. By testing different glazing ratios, insulation levels, and wall materials, architects can make more informed design decisions early in the process.
Building performance consultants and sustainability specialists can use DecarbFit as a rapid screening tool to compare envelope options before investing time in detailed simulations or life cycle assessments. The tool can help identify promising design directions that warrant further analysis.
Developers and owners may use the tool to understand the tradeoffs between upfront construction costs and long-term carbon reduction goals. This can support conversations around sustainability targets and investment decisions.
Students and educators can also use DecarbFit as a learning tool to better understand the relationship between building form, envelope design, operational performance, and embodied carbon.
The Need
Building decarbonization is becoming a major priority across the architecture, engineering, and construction industry. However, many carbon-related decisions are still evaluated too late in the design process, often after major envelope and material selections have already been made.
Existing carbon assessment tools typically require detailed building information, extensive material quantities, or specialized software platforms. Similarly, energy modeling tools often require significant setup time and technical expertise before meaningful results can be generated.
As a result, designers frequently lack accessible tools that provide immediate feedback during early-stage design exploration.
DecarbFit helps bridge this gap by providing a simple, BIM-friendly workflow that connects envelope design decisions with carbon, cost, and energy performance metrics. Instead of waiting until later project phases, users can evaluate the implications of their decisions while the design is still flexible and alternatives can be explored efficiently.
The goal is not to replace detailed simulation or life cycle assessment software, but rather to provide a fast and intuitive decision-support tool that encourages carbon-conscious design from the beginning of the project.
DecarbFit estimates the carbon, cost, and energy implications of a simplified building envelope. Users can modify building dimensions and envelope characteristics, and the tool automatically calculates key performance indicators that support early-stage decision-making.
The primary purpose of the tool is to visualize tradeoffs between competing design objectives. For example, increasing insulation thickness may reduce operational energy demand but increase embodied carbon and construction cost. Similarly, selecting a lower-carbon wall material may reduce emissions while affecting project budget.
By presenting these metrics together, DecarbFit helps users identify envelope strategies that achieve a better overall balance between environmental performance and economic feasibility.
The workflow begins with a series of adjustable design inputs that define the building geometry and envelope characteristics.
Users can modify building dimensions, number of floors, glazing percentage, insulation thickness, and wall material selection. Once these inputs are updated, the model automatically recalculates the building envelope quantities and associated performance metrics.
The resulting outputs provide a quick comparison of different design alternatives and can be used either as a standalone design aid or as part of a Generative Design workflow.
When used with Generative Design, DecarbFit can evaluate hundreds of envelope combinations and identify solutions that balance carbon reduction, energy performance, and cost objectives.
Key metrics available for comparison include:
- Embodied Carbon
- Material Cost
- Annual Energy Demand Proxy
- Operational Carbon Proxy
- Overall DecarbFit Score
Underlying Model Logic
The Dynamo or Grasshopper workflow is organized into five primary stages: geometry generation, envelope calculations, carbon calculations, energy calculations, and performance scoring.
The process begins by generating a simplified rectangular building mass using the user-defined building length, width, and number of floors. A constant floor-to-floor height is applied to determine the overall building height.
Using this geometry, the model calculates:
- Gross floor area
- Building perimeter
- Total façade area
- Roof area
- Total envelope area
Next, the window-to-wall ratio is applied to the façade area to separate the envelope into two components:
- Window area
- Opaque wall area
Once these quantities are established, material assumptions are assigned to the opaque wall assembly. Each wall material option contains predefined embodied carbon factors and cost factors based on area. Insulation thickness is then applied to calculate additional material quantities, embodied carbon contributions, and construction costs.
For operational performance, the model uses a simplified energy demand proxy. A baseline annual energy demand is adjusted according to envelope characteristics. Increased insulation thickness reduces the energy demand proxy, while higher glazing ratios increase the energy demand proxy due to assumed heat gain and heat loss effects.
The adjusted annual energy demand is then multiplied by an electricity carbon intensity factor to estimate operational carbon emissions.
Finally, all performance metrics are normalized and combined into a single DecarbFit Score. This score allows users to compare alternatives using a balanced metric that considers embodied carbon, operational carbon, and material cost simultaneously.
The resulting outputs can be displayed directly within Dynamo or Grasshopper and can also be used as objectives within a Generative Design study.
Inputs
1) Design Variables
- Building Length (ft or m)
- Building Width (ft or m)
- Number of Floors
- Window-to-Wall Ratio (%)
- Insulation Thickness
- Wall Material Selection
- Conventional Concrete/CMU
- Steel Stud Assembly
- Timber-Based Assembly
- Low-Carbon Wall Option
2) Project Assumptions (Constants)
- Floor-to-Floor Height
- Baseline Annual Energy Demand
- Electricity Carbon Intensity
- Wall Material Carbon Factors
- Wall Material Cost Factors
- Window Cost Factor
- Window Carbon Factor
- Insulation Carbon Factor
- Insulation Cost Factor
- DecarbFit Score Weighting Factors
Outputs
- Gross Floor Area
- Building Height
- Total Façade Area
- Opaque Wall Area
- Window Area
- Estimated Embodied Carbon
- Estimated Material Cost
- Annual Energy Demand Proxy
- Estimated Operational Carbon
- Overall DecarbFit Score
- Generative Design Performance Dataset
My original concept was significantly broader and focused on creating an AI-powered platform called DecarbRx. The vision was to analyze BIM models and Bills of Quantities, identify carbon hotspots, and generate recommendations for reducing embodied and operational emissions across an entire building project.
While that concept remains a long-term goal, it would require extensive data integration, machine learning workflows, and advanced analysis capabilities that are beyond the scope of this course project.
To create a realistic and achievable prototype, I narrowed the focus to one specific design challenge: envelope optimization. By limiting the scope to envelope-related decisions, I can still demonstrate the core idea of carbon-informed design assistance while developing a functional tool within the available timeframe.
The simplified version retains the most important aspect of the original vision—helping designers make better sustainability decisions earlier in the design process.
DecarbFit is a parametric decision-support tool that helps designers evaluate low-carbon envelope strategies during the earliest stages of building design. By connecting geometry, material selection, insulation, glazing, cost, and carbon performance into a single workflow, the tool provides immediate feedback that supports more informed decision-making.
The primary value of DecarbFit is its ability to reveal tradeoffs between embodied carbon, operational carbon, and construction cost before detailed analysis is performed. Rather than focusing on a single performance metric, the tool encourages a more holistic approach to sustainable design and helps users identify envelope solutions that achieve a balanced overall outcome.