Achieving more climate-friendly concrete masonry involves reducing the amount of embodied carbon, as well as the amount of operational carbon in the buildings constructed with concrete block masonry. Embodied carbon is the carbon emissions resulting from the extraction, manufacturing, delivery, installation, and disposal of the product. Operational carbon creates emissions resulting from the use of the building, such as HVAC, lighting, and power. With concrete masonry, substituting Portland Limestone cement (GUL) for General Use Portland cement (GU) in the manufacture of concrete masonry products and accelerating carbon sequestration by pre-carbonation can reduce embodied carbon emissions. Operational carbon can be reduced by taking advantage of the thermal mass effects of concrete masonry. This improved thermal modeling creates concrete masonry assemblies that mitigate the loss of thermal energy and reduce the amount of heating or cooling a building requires during operation.
Concrete masonry can be used to create backup walls and claddings that can meet the requirements of net-zero energy building envelopes, eliminating operational carbon from heating. Their long service life requires little maintenance and offers an even better carbon footprint when the embodied carbon and operational carbon are amortized over the life of the building. These products are cradle-to-cradle rather than cradle-to-grave, as concrete masonry is 99 percent recyclable at the end of service.
This article will explore Environmental Product Declarations (EPDs) currently available for concrete masonry products and carbon sequestration of concrete masonry units in weathering carbonation and pre-carbonation of CMUs. The article will also explore achieving net-zero energy buildings (passive house) by introducing improved values to more accurately account for thermal bridging in concrete block-brick veneer walls. It will also explain the use of a low-rise concrete masonry building achieving the net-zero energy requirements for opaque and fenestration and doors of passive house.2 The article will conclude with the benefits of the thermal mass effects of concrete masonry on reducing operational carbon.
EPDs for concrete block
An EPD is a document that communicates the environmental impact of any product or material over its lifetime. In the construction industry, EPDs support carbon emission reduction by providing comparisons of the impact of different materials and products to select the most sustainable option. Architects, engineers, and designers can choose the most sustainable option for their project, while manufacturers can optimize the impact of their products and market their carbon transparency. An EPD is usually valid for five years and is generated according to ISO 14040/14044, ISO 14025, EN 15804, or ISO 21930 standards.3
