Life cycle assessment

Life Cycle Assessment (LCA) is a systematic analysis of a building’s environmental impacts throughout its entire life cycle-from the extraction of raw materials for construction materials, through the construction phase and operation, to demolition and disposal. In modern sustainable construction, the life cycle assessment is a key evaluation tool: building standards such as QNG (Quality Seal for Sustainable Buildings) and DGNB require a life cycle assessment and link it to eligibility for funding.

Components of a Building Life Cycle Assessment

The life cycle assessment captures primary energy demand (renewable and non-renewable), global warming potential (GWP, measured in CO₂ equivalents), acidification potential, resource consumption, and waste generation. A distinction is made between:

Grey energy: Energy and CO₂ emissions embodied in building materials-from raw material extraction, manufacturing, transportation, and installation. This phase is covered in Modules A1-A5 of the life cycle assessment. For a conventionally insulated single-family home, manufacturing emissions alone can amount to 40-80 tons of CO₂ equivalents.

Operational energy: Heating, hot water, ventilation, lighting, and cooling over the building’s service life - captured in Module B6. As energy efficiency increases (KfW 40, Passive House), operational energy decreases, while gray energy becomes relatively more significant.

For modern energy-efficient buildings, embodied energy now accounts for 50-80% of total life-cycle emissions-an increasingly important factor in material selection that is often underestimated.

Life-cycle phases in detail

A complete life-cycle assessment according to ISO 14040/14044 considers the following phases:

Module	Phase	Content
A1-A3	Product phase	Raw materials, production, manufacturing
A4-A5	Construction phase	Transportation, construction site operations
B1-B7	Use phase	Operation, maintenance, replacement
C1-C4	Disposal phase	Demolition, transport, landfill
D	Outside the life cycle	Recycling potential (informative)

For assessments within the framework of QNG and BEG funding, modules A1-A3 (manufacturing) and B6 (operational energy) are typically used.

Building Material Comparison: Embodied Energy of Various Insulation Materials

The choice of material has a significant impact on the life cycle assessment. Nature-based insulation materials often perform significantly better than fossil-based or mineral alternatives:

Insulation Material	GWP [kg CO₂eq/kg]	Special Feature
EPS (Styrofoam)	approx. +3.5 to +5.0	fossil-based, poor life cycle assessment
XPS (extruded polystyrene)	approx. +4.5 to +7.0	blowing agent problematic
Mineral wool	approx. +1.5 to +2.5	energy-intensive production
Cellulose (blow-in insulation)	approx. −0.5 to +0.5	CO₂-neutral (recycled paper)
Wood fiber board	approx. −1.5 to −0.5	CO₂ sink (renewable)
Sheep’s wool	approx. +2.5 to +4.0	renewable, regional

Negative GWP values mean that the building material sequesters net CO₂-an advantage that EPS and mineral wool do not offer. With the same thermal insulation performance, cellulose insulation is two to three times better in terms of life cycle assessment than EPS.

Life Cycle Assessment as a Funding Requirement and Market Factor

The Federal Ministry of Housing has introduced a life cycle assessment requirement for subsidized new buildings (KfW Efficiency House Standard, QNG). Anyone applying for federal funding for efficient buildings (BEG) for new construction and wishing to utilize the KfW program “Climate-Friendly Buildings with QNG” must provide proof of a life cycle assessment by a certified assessor. The threshold for global warming potential is set at a maximum of 6 kg CO₂eq/(m²·a), based on the living area over a 50-year period.

Furthermore, the life cycle assessment is gaining importance as a market factor: ESG-compliant investors and institutional buyers are increasingly demanding proof of a building’s climate impact. With the EU Energy Performance of Buildings Directive (EPBD), it is expected that life cycle greenhouse gas potentials will also be legally mandated for all major new buildings in the future.

Material Selection and Life Cycle Assessment in Renovation

Life cycle assessment is also playing a growing role in renovation projects. Renewable raw materials (wood, cellulose, sheep’s wool as insulation materials) often perform better in life cycle assessments than mineral or petroleum-based materials (EPS, XPS). For older buildings in Nuremberg and Franconia-especially Wilhelminian-style buildings with brick masonry-we recommend vapor-permeable insulation solutions such as wood fiber boards or interior insulation with calcium silicate. These are not only more favorable in terms of life cycle assessment but also safer from a building physics perspective for moisture-sensitive historic structures.

We recommend that owners consult an energy consultant for renovation projects to assess the life cycle assessment of the planned measures-rather than simply optimizing the thermal transmittance coefficient (U-value).

Practical Tip for Owners in Nuremberg and Franconia

In Nuremberg and the metropolitan region, there is a growing number of architecture and planning firms specializing in green building and life cycle assessment. If you are planning a renovation project and wish to utilize federal funding, speak with a certified energy consultant early on about the life cycle assessment requirements-providing proof after the fact is often more time-consuming and expensive than forward-thinking planning.

Anyone planning a new construction and aiming for the QNG seal should have their material choices (insulation, structural framework, building services) reviewed for their life cycle impact as early as the design phase. The cost of a professional building life cycle assessment ranges from 1,500 to 5,000 euros-a manageable amount relative to the subsidy savings achieved through the higher KfW rating. We can connect you with experienced specialist planners in your region.

Frequently Asked Questions

Do I need a life cycle assessment for the renovation of my existing building?

For private renovations without federal funding, a life cycle assessment is not mandatory. However, if you apply for individual BEG measures or a KfW loan for a renovated Efficiency House standard, proof of a life cycle assessment may be required depending on the program conditions. For the QNG seal on new buildings, however, it is mandatory.

How much does a life cycle assessment for a residential building cost?

Simple life cycle assessments for single-family homes start at approximately 1,000 to 2,000 euros. More complex life cycle assessments for multi-family homes or new buildings with QNG certification cost 2,000 to 5,000 euros-depending on building size, variety of materials, and level of detail. The Federal Institute for Research on Building, Urban Affairs and Spatial Development (BBSR) provides eLCA, a free calculation tool that, however, requires specialized knowledge.

Does a good life cycle assessment improve a property’s selling price?

Not directly at this time, but demand for verifiably sustainable buildings is growing-especially among institutional buyers and those with a long-term perspective. In the medium term, buildings with poor life cycle assessments will lose value due to stricter EU regulations (the EPBD) and rising CO₂ prices. An investment in sustainability protects value in the long term-and can already be used today as a marketing argument for buyers who prioritize ESG and sustainability.

Is cellulose insulation really better than mineral wool?

In terms of the life cycle assessment, yes-cellulose insulation has significantly lower embodied energy than mineral wool and is CO₂-neutral to slightly CO₂-sequestering. Sound insulation is also often better with cellulose. The difference in purchase costs is minimal. Limitations: Cellulose is not suitable for all applications (e.g., not for surfaces in contact with the ground, limited use on flat roofs). A specialist planner should assess its suitability for the specific application.

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