By Magdalena Patyna

On a global scale, the energy needed to produce building materials currently plays a small role compared to the energy that buildings consume in operation. In 2022, around 30% of global final energy use was attributed to building operation, while the construction industry (materials) accounted for just 4%. And, within the lifespan of a building, operational energy usually dominates a building’s overall balance—especially when it’s not designed for high efficiency. So, efficiency first during the building’s operation remains the cornerstone principle for those interested in transforming the built environment.

But, that does not mean we can, or should, ignore the consumption of resources as well as the resulting carbon impacts of our material choices. Understanding their impact gives us the chance to make well-informed decisions, support the market penetration of low-energy material alternatives, and make sure the effort we put into optimization is directed where it really counts. This is where the new Manufacturing Energy Evaluation Toolkit (MEET) comes in. One of its tools, MEET 2, takes the results from the PHPP (Passive House Planning Package) and allows us to answer the question: “For the materials I select, what is the manufacturing energy and global warming potential (GWP) impact, and what does that mean in relation to the building’s operational part?” In short, MEET makes it possible to consider both manufacturing (embodied) and operational environmental impacts side-by-side in a single, practical workflow—without leaving Excel.

MEET 2 is currently in its beta stage. Being a work in progress, this is the perfect time for your feedback, as it will directly shape how the tool develops.

Behind the Numbers of MEET

PHI developed the toolkit with the following considerations and boundaries. As ensuring comparable results with the PHPP was a primary goal, in MEET, the results are intentionally presented annually, enabling direct comparison with annual operational energy and different assessment periods.

Instead of looking only at GWP, PHI also considers manufacturing primary energy (renewable and non-renewable) as part of the embodied assessment, as energy demand is a key indicator of production efficiency. While GWP (as a measure of climate impact) heavily depends on local factors like the energy mix in the production country and can quickly change over time, manufacturing energy provides a more robust measure and is internationally more comparable. This avoids overlooking opportunities for energy savings, as energy that is avoided does not need to be provided at all–whether from fossil or renewable sources.

MEET‘s system boundary was defined as including the manufacturing stage (A1–A3, as defined in EN 15804: raw material supply, transport, production) and the use stage (B, operation and replacement after completion of construction). These are the phases with the most relevant and reliably quantifiable impacts. Speculative scenarios far in the future (reuse, disposal, recycling) are excluded, as these are highly uncertain, especially considering anticipated advances in circular economy and renewable energies. Caloric energy (the energy stored in materials: PENRM, PERM) is also not considered, as it is not decisive for ecological optimization within this context. The service life, and thus the replacement cost of the materials, implicitly enters through the annual presentation of results. We recommend an assessment period of 40 years. While this is much shorter than the expected lifetime of a building, it represents a timeframe that can still be meaningfully assessed according to MEET’s method.

The embodied carbon of wood is a much-debated topic. Based on the current state of scientific literature, we apply a reduction of 60% to the biogenic CO2 credits usually attributed to wood products, thus counting only 40% of the credit. This adjustment ensures more realistic results while still considering the positive benefits of the material. For other fast-growing biogenic materials, such as straw, the full credit is retained, as these would otherwise release nearly all of their stored CO2e if not used as construction products.

MEET already includes a comprehensive material database. Values have been initially tailored to the German region (with the ÖKOBAUDAT as a main source), but compared to GWP, manufacturing energy shows far less variation between countries. Therefore, the manufacturing energy figures can also serve as a good-enough approximation for other regions.

Still, users can choose to manually add their own data. Standard databases such as ÖKOBAUDAT and third-party EPDs can be used, with manual recalculation where necessary to align with MEET’s method.

Want to dive deeper? See this Passipedia article about the method, which is available to iPHA members.

Practical Guidance

Here is a step-by-step guide to getting started with MEET.

• Start by modelling your project in PHPP and then link it with MEET via the interface worksheet to transfer the data. The interface worksheet can be requested as described here. In MEET, complete the inputs, check the BALANCE sheet to see what drives the results, and refine the design where it has the greatest impact.

• Use PHPP to reduce the energy demand; use MEET to compare envelope and component options; then revisit PHPP to refine your choices.

• Compare assemblies systematically: in heating-dominated climates, transmission losses strongly correlate with total demand. Thus, create several possible options of thermal envelope components (walls, roofs, windows...) in PHPP, even if you don’t apply them in your PHPP project. In MEET, you can then evaluate how the manufacturing energy and resulting GWP relate to the theoretical transmission losses per m² of the component. You can find the comparison charts in the input sheets “Opaque assemblies” and “Windows&Doors” to the right. For cooling-dominated climates, it is better to create PHPP variants and track the resulting outcomes of each variant.

Focus Where It Counts

Three takeaway lessons have been drawn from the use of PHPP and MEET. These takeaways highlight the main levers for climate impact in our projects, starting with the strongest lever. But don’t forget: outcomes will always depend on the specific project and region, especially when it comes to GWP.

1. An efficient building envelope and ventilation with heat recovery significantly reduces operational energy demand—and with it, the project’s overall greenhouse gas emissions. As a side effect, this also allows for smaller technical systems with lower manufacturing energy.

2. The use of renewable energy and an efficient source of heat generation, such as a heat pump, is critical.

3. Once operational energy is genuinely low, optimizing materials and building components becomes the next effective step. Here, durability is just as important as manufacturing values: the longer a material lasts without replacement, the more favorable its overall contribution becomes over the building’s lifetime.

Two Case Studies--New Construction and Retrofit

The three takeaways the PHI outlined aren’t just theory; they can be demonstrated through real projects. Here we show two examples: a new school building and the retrofit of a multi-family home (see Figure 1).

Further Links

The toolkit also includes two free web tools:

• MEETonline Building Assembly Comparison – for comparing two opaque building envelope components.

• MEETonline Building LCA Calculator – for generating a quick concept of a predefined single-family home.

You are welcome to try them out. They offer an easy way to familiarize yourself with lifecycle thinking.