Masonry—bricks and blocks—can be structural or a cladding veneer. They provide a durable wall system at the hands of skilled local labor, and a time-honored, traditional look.
Manufacturing causes high energy use, pollution
The bricks and blocks that comprise masonry are typically either cement-based, or fired, as with brick or terra cotta products. Mortar is also usually cement-based. Whether it’s the blocks themselves or the cement used to make them that come out of a kiln, they are relatively energy-intensive and polluting to produce.
Lower-impact bricks, blocks, and even faux stone veneers are available made from pozzolans or alternative cementitious materials, such as coal fly ash or ground-granulated blast furnace slag.
Thermal and moisture protection
Most masonry products don’t offer much thermal insulation value, so we need to look to other parts of the assembly for that. Some products are designed to accommodate those insulating layers and provide for thermal breaks between the masonry elements. Integrated appropriately into an assembly, many masonry assemblies can serve as rain screens, with an air cavity behind. That type of assembly works well to prevent rain penetration into wall cavities, as long as joints and opening are detailed appropriately.
Concrete masonry units (CMUs) made from autoclaved aerated concrete (AAC) are lighter than conventional CMUs, generally have no cores, and provide higher insulation levels. They have R-values of up to 1.25 per inch, which are an order of magnitude higher than standard concrete, but still not sufficient to meet some energy goes without resorting to extremely thick walls.
Traditional alternatives to brick and block
Made from soil that has suitable sand and clay content and then air-dried in the sun, adobe bricks typically have extremely low greenhouse gas emissions and embodied energy.
Stone remnants from quarries are typically discarded but they can be used to provide a durable masonry cladding, sometimes called “sculpings,” that substitutes for more energy-intensive materials.
Heating with wood, in a masonry fireplace
When wood is locally available and can be harvested sustainably, it has no net impact on global warming—because the carbon emissions from combustion are more than compensated for by growing trees. Masonry fireplaces are designed to hold quick-burning, hot fires that minimize pollutant emissions, while holding and distributing heat over a long period of time.
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