LCA for Renovated Buildings

LCA for Renovated Buildings#

This page provides a practical summary for a DGNB Compliant LCA Calculation for renovated buildings. LCA is a collaborative tool that helps teams understand trade-offs across disciplines. By modeling environmental impacts early, you can use LCA to inform your team’s design decisions, justify material selections, and challenge assumptions about sustainability. Discussing LCA results across teams (e.g., architecture, engineering, sustainability) encourages shared priorities and supports transparent decision-making. It’s especially useful when evaluating renovation strategies where teams must balance heritage, performance, and embodied carbon. Encourage your group to use LCA results as a conversation starter, not just a final number.

1. Define Your LCA Scope#

  • Timeframe: 50 years (as per DGNB and EN 15978).

  • Functional unit: 1 m² of gross floor area (GFA) over 50 years.

  • Life cycle stages:

    • A1–A3: Material production

    • B4: Replacements (e.g., windows, HVAC)

    • B6: Operational energy (heating, cooling, lighting, etc.)

    • C3–C4: End-of-life (demolition, disposal)

    • D: Reuse/recycling benefits (report separately)

2. Collect Input Data#

  • Material quantities:

    • From BIM/Revit models or renovation drawings.

    • Include insulation, windows, HVAC, façade cladding, etc.

  • Product data:

    • Use EPDs (Environmental Product Declarations) – prioritize product-specific EPDs.

  • Replacements:

    • Find expected service lives (e.g., paint every 10 years, windows every 30 years).

    • Multiply original material impact by number of replacements.

  • Operational energy:

    • Estimate annual consumption (kWh/m²/year) for:

      • Electricity

      • Heating

      • Possibly cooling and DHW

    • Include updated systems post-renovation.

  • Emission factors:

    • Use national values or DGNB defaults (e.g., kg CO₂e/kWh for electricity and heating).

3. Model in LCA Software (e.g., SimaPro)#

1. Start a New Project#

Name your project and define the functional unit (e.g., “1 m² renovated area / 50 years”).

2. Build the Life Cycle Inventory (LCI)#

For each material:

  • Use SimaPro’s library to find the closest EPD or generic dataset (e.g., mineral wool, aluminum window frame).

  • If EPD is not available, input data manually using process creation.

  • Input quantities per m² or for the entire building, then normalize later.

3. Model Replacements (B4)#

  • Multiply initial material amounts by the number of expected replacements within 50 years.

  • Add as separate processes or increase the quantity accordingly.

4. Add Operational Energy (B6)#

  • Select “Electricity, low voltage, DK mix” or other relevant sources.

  • Multiply annual use by 50 (or enter total for 50 years).

  • Include both regulated and unregulated energy, if required.

5. End-of-Life (C3, C4) and Module D#

  • Add disposal processes (e.g., landfill, incineration).

  • Include recycling credits in Module D but report them separately.

6. Select Impact Assessment Method#

  • Use EN 15804, CML-IA, or ReCiPe Midpoint.

  • Focus on GWP (kg CO₂e) and other DGNB categories: AP, EP, POCP, ADP, etc.

7. Run Calculation#

  • Analyze total environmental impacts.

  • Break down by life cycle stage and material where possible.

8. Normalize Results#

Convert total impact to:

  • kg CO₂e/m² over 50 years

  • or kg CO₂e/m²/year for DGNB comparison

4. Calculate Environmental Impacts#

  • Use EN 15804 or CML impact method.

  • Focus on:

    • GWP (Global Warming Potential) – in kg CO₂e/m²/year.

    • Also include Acidification (AP), Eutrophication (EP), and other DGNB impact categories.

  • Normalize total impacts to: * kg CO₂e/m²/50 years * or kg CO₂e/m²/year (for DGNB comparison)

5. Interpret the Results#

  • Identify carbon hotspots (e.g., insulation, HVAC, operational energy).

  • Compare results with DGNB target: * Aim for <9.4 kg CO₂e/m²/year for DGNB Gold level.

  • Optional: Do sensitivity analysis (e.g., changing façade material, using greener energy).

6. Document for DGNB and Reporting#

Include:

  • Material list and quantities

  • EPD references

  • Energy use assumptions

  • Life cycle stage breakdown (A, B, C, D)

  • Final GWP result (kg CO₂e/m²/year) Use tables and graphs to present:

  • Impact per life cycle phase

  • Contribution by building element

Tips

  • Follow DGNB rules for system boundaries and exclusions (ignore screws, nails, <1% rule).

  • Always document your assumptions.

  • Keep LCA modular and simple—start with key materials, refine later.

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