The IPCC (Intergovernmental Panel on Climate Change) estimates that 21% of greenhouse gas emissions are linked to the construction sector. As many new buildings continue to be constructed, concrete blocks masonry should be considered: it is a low-carbon construction solution. Impact of masonry on climate change can be assessed by the already published Environmental Product Declarations based on EN15804 as well as the “Product Category Rules for concrete and concrete elements” EN16757. To illustrate the necessary distinction to be done between direct, indirect emissions and embodied emissions in buildings, a quantification of the impact on climate change related to the energy consumed during the building operation on the one hand, and construction products and building equipment and their implementation on the other, is presented for a single-family house as well as the specific contribution of infrastructure and superstructure to its total Global Warming Potential (GWP). Calculated GWP for different types of masonry walls are then given. They show how important it is to base a declaration on a functional unit rather than a declared unit for the eco-design of a building. By analyzing the relative contribution of each life-cycle stage to the Global Warming Potential of different types of masonry, levers for reducing and optimizing the design, manufacture and installation are quantified for different concrete masonry units. To support innovation, technical certification has been set up to guarantee safe use and durability of concrete blocks manufactured with low carbon binders as well as for concrete blocks incorporating aggregates recovered during manufacturing or recycled from deconstruction.