Practical Residential Wall Systems: R-30 and Beyond
With uncertainty of energy prices and an increased interest in sustainability, more builders and designers are striving for dramatic levels of home energy efficiency. Performance of the home’s envelope is clearly critical in this endeavor. In colder climates, several builders are moving towards whole-wall thermal resistances above 30 ft2hr°F/Btu (4.9 m2°C/W). While there are numerous high-performance wall systems, the authors focus here on three of the most practical methods to achieve whole-wall performance of R-30 or above. Working with builders in cold climates, the authors have found that these three approaches are often the most well-established, use readily available materials, and are buildable by contractors without substantial additional equipment or sub-contractors: Double framed walls with blown or sprayed insulation; 2x4 or 2x6 insulated, framed walls with exterior rigid foam insulation; and structural insulated panels (SIPs).
This paper documents key components, advantages, and challenges for each wall system including: material choices and options; structural issues, durability, and moisture management; requirements of builders and trades (framing, insulation, plumbing, electrical, and siding; etc.); and cost considerations.
The “best” choice for a wall system will vary with region, with fluctuating material prices, with building design and type, and with builder experience and preference. From experience working with builders using these techniques, the authors have prepared this paper to provide key considerations and guidelines for designing and building homes using these wall systems and achieving at least R-30 performance.