Evaluating R-40 Above Grade Walls for a Production Built Zero

As part of Building America research for developing and implementing zero energy houses on a widespread basis, IBACOS conducted research on what constitutes a high performance exterior wall assembly for this level of energy-efficient construction.

Our research focused on exterior walls in a cold climate zone and considered their constructability, installation, cost, durability, and thermal performance. Our research included an examination of wall design considerations including: drying potential, thermal bridging, flashing details, and structural details. We used a variety of modeling software to obtain information, including TRNSYS, WUFI®, EnergyGauge USA, and THERM. We built some of the wall systems in a laboratory setting to better evaluate their constructability.

Here, we look at the best wall assemblies that emerged from our research and why they were chosen. This paper also covers the evaluation process used in the research, design challenges encountered, the construction details researched, the detailed costing information developed. The goal is to offer lessons learned for builders and designers who strive to achieve exceptional energy efficiency in houses.