CARB Home

The Department of Energy’s (DOE) Building America Program is a partnership between researchers and the various facets of the residential building industry with the intent to improve the quality and energy efficiency of homes. The goal is to develop cost effective solutions that reduce the average energy use of housing by 40% to 100%. Ultimately, Building America research will lead to net zero energy homes, which produce as much energy as they use over the course of a year.

The Consortium for Advanced Residential Buildings (CARB) is one of six residential research teams that are funded through this program, with Steven Winter Associates, Inc. (SWA) as the lead team member. The primary focus of SWA’s research is systems-integration and new technologies, all with the ultimate goal of achieving net-zero energy homes. We invite you to take a look at our case studies and newsletters to learn more about our homes and projects that have been a part of this research program.

It is evident that there is a steady increase in the use of High-R walls in cold climate residences. Reduced utility bills, increased indoor thermal comfort and a growing interest in energy efficient homes are some of thereasons why builders and homeowners are moving towards incorporating high performance wall systems in their homes. Although various such wall systems are available, CARB researchers, based on their experience working with builders in cold climates, discuss three well established wall systems – double walls, foam sheathed frame walls and Structurally Insulated Panels (SIPs) in this paper.

Increased levels of insulation in the walls come with a set of challenges which is the focus of this research. It highlights the pros and cons of each wall system including material choices, structural stability, moisture issues, code concerns, cost considerations and implications for builders and related trades. This paper titled “Residential wall Systems: R-30 and beyond” is being presented at the BEST2 conference (Building Energy Science and Technology) in Portland, OR in April 2010.

A condensed version of this paper can be accessed here.

CARB partnered with Green Builder Media and Building Media Inc. on a deep retrofit house in Las Vegas. This ranch home built in 1963 is a single story 1800 sq.ft home with low pitched roofs, post and beam construction, vaulted ceilings and huge windows. CARB’s responsibilities ranged from initial inspections, testing, performance analysis, recommendations and data monitoring. Recommendations included exposing the walls from the outside to swap out the old fiberglass batt insulation in the 2x4 walls with 3-1/2” foam yielding an R value of 13.62 (at R-3.9 per inch) and introduce structural sheathing along with 2” of expanded polystyrene (EPS) insulation resulting in a total R-value of 21.65. Read more about the various recommendations, products and systems that make this house a success by clicking on the links below. CARB calculated the home’s HERS score from its pre-retrofit high of 123 to a -2 (with a 5.67kW rooftop PV installed), making this a net-zero energy home. Without the PV, the home achieves a very respectable HERS score of 44.

Through Building America, many innovative strategies have been developed to achieve whole‐house energy efficiency. Though case studies, lab testing, and field monitoring have demonstrated the viability of these strategies, it seems that comprehensive documentation is still lacking on details for architects and builders to utilize during the design stage. Details may focus on the thermal barrier or the air barrier or the water barrier, but often these are not spelled out in a concise document that details the sequencing of these three key elements. Through various current builder projects, CARB is amassing various details (advanced framing, air sealing, thermal bypass prevention, wall assembly sequencing, foundation insulating, etc.) that we intend to add to our website. Below are a few details on advanced framing and air sealing.

Air Sealing Part I

Air Sealing Part II

Advanced Framing Part II