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Use Rammed-Earth Walls

Tags: New construction, exterior walls/roofs, cold, dry, hot_humid, marine, mixed_humid, Structural Systems & Components

A traditional building method, rammed earth uses soil compressed into forms to make thick walls.

The soil must contain an appropriate mix of particle types and sizes to bond well and to avoid excessive shrinking. Occasionally, a small amount of stabilizing cement is added. A modern less labor-intensive variation on rammed earth uses gunite technology (similar to sprayed-in-place swimming pools) to shoot a soil mixture into the form.

Because the walls are so thick (12-in. to 16-in.), rammed-earth structures have good thermal mass—warming and cooling gradually to even swings in temperature variation. But, for the same reason, similar to concrete, rammed-earth walls also require insulation in cooler climates.

Again because of wall thickness, even a low proportion of cement stabilizer can result in using more cement than in a standard concrete wall. And, in seismically active areas, one of the main benefits of this low-impact process is overshadowed by the large amounts of cement and reinforcing steel required.

Green points

LEED for HomesLeadership in Energy and Environmental Design. LEED for Homes is the residential green building program from the United States Green Building Council (USGBC). While this program is primarily designed for and applicable to new home projects, major gut rehabs can qualify. : Wall system influences thermal performance, potentially affecting 3 to 5 points in EA1 (Energy & Atmosphere), EA2, and/or EA3. Alternative walls are not de facto environmentally preferable; a credit interpretation request (CIR) may be submitted under MR2.2 (Materials & Resources).

NGBSNational Green Building Standard Based on the NAHB Model Green Home Building Guidelines and passed through ANSI. This standard can be applied to both new homes, remodeling projects, and additions. /ICC-700: Under Chapter 7, "Energy Efficiency": High mass alternative wall systems contribute up to 4 points as part of passive solar design (704.3.1,.3-.4). Under Chapter 6, "Resource Efficiency": 2 points for each indigenous component, e.g., straw (608.1); up to 8 points for bio-based systems, such as bamboo, straw, and cob (606.1).