Global Warming Potential (GWP) is the unit used to measure how much a material, process or building contributes to the greenhouse effect. It’s expressed in kg CO₂-equivalents (kg CO₂-eq), which allows different greenhouse gases to be compared on a single scale.
Why does it matter to you?
When choosing building materials for a renovation or new build, the GWP value tells you the real climate impact. It’s not enough to trust marketing claims about “sustainable” products — the GWP reveals whether a material is genuinely better for the climate than the alternative.
Danish building regulations (BR18) require new buildings over 1,000 m² to document their total GWP through a life cycle assessment. The current limit is 12 kg CO₂-eq/m²/year.
How it works
GWP is calculated for each individual material via an EPD (Environmental Product Declaration). The sum of all materials’ GWP values feeds into the building’s overall LCA calculation.
Typical GWP values for common building materials:
- Concrete (1 m³): approx. 200–350 kg CO₂-eq
- Steel (1 kg): approx. 1.5–2.5 kg CO₂-eq
- Structural timber (1 m³): approx. -300 to 0 kg CO₂-eq (stores carbon)
- Mineral wool (1 m²): approx. 3–7 kg CO₂-eq
Frequently asked questions
Is GWP the same as CO₂ emissions?
Almost. CO₂-equivalents include all greenhouse gases (CO₂, methane, nitrous oxide etc.) converted to a single unit. It’s more accurate than measuring pure CO₂.
Where can I find a material’s GWP?
In the product’s EPD, typically available from the manufacturer or in open databases such as ECO Platform or OEKOBAUDAT.
Does timber have a negative GWP?
Often yes, in the production phase — timber stores CO₂ absorbed during tree growth. However, this benefit diminishes or reverses when the timber eventually decays or burns. Full LCA accounting considers the entire lifecycle.