Vapor Diffusion-Open Walls Study

Project Page

CCHRC monitored the performance of Fairbanks builder Thorsten Chlupp’s passive solar home over one year. The superinsulated house demonstrates innovative building and mechanical systems, with a super-insulated foundation, integrated heat storage system, and an open wall design that allows vapor to diffuse through. This home shows that buildings can perform well without traditional heating systems even in a subarctic climate, and provides a new option for high-efficiency construction. The goal is to learn how to optimize this integrated heating system to make it more cost-effective in the future. The wall design does not include a vapor barrier, allowing the wall todry to either the interior or the exterior, and places an air barrier between two dense-pack cellulose masses. Sensors placed in the wall recorded temperature, relative humidity, and moisture accumulation in the walls for 13 months.

Walls

The primary concern of the wall system is the potential for moisture buildup and, subsequently, mold growth.  A data analysis revealed that the humidity and moisture content in the wall do not experience the levels and duration required for mold growth. In addition, moisture does not appear to build up in the wall over time. Rather, moisture is transient, and the direction of moisture transport varies seasonally and diurnally, which supports the basis of the wall design.

Foundation

The R-60 rigid insulation around the foundation was intended to reduce energy loss from the building to the ground. This study looked at how well the insulation prevents heat loss and whether it causes frost heaving of the ground. Temperature sensors were located in the soils beneath and next to the house.

Monitoring showed that the insulation in the foundation was not enough to completely thermally isolate the house from the ground. However the soil temperatures down to 7 feet never froze, which mitigates potential for frost heaving.

PDF icon Subarctic Passive House Case Study

PDF icon Arctic Wall Performance 

 

Read more about the house on Thorsten Chlupp's website here.

Related Topics & Keywords: 

Projects

Slab-on-Grade Foundation Best Practices An evaluation of best practices for insulating under slab-on-grade foundations
Garage Wall Analysis CCHRC is looking at attached garages to see if they adequately prevent pollutants from entering the house.
Vacuum Insulated Panel Test CCHRC is testing how Vacuum Insulated Panels can be assembled to achieve extremely high R-values in cold climate homes.
Designs for Rural Alaska Walls Monitoring CCHRC demonstration homes for efficiency and moisture infiltration several years after construction.
Structural Insulated Panels Structural Insulated Panels (SIPs) are prefabricated building materials used in residential construction in Alaska. This project prepared resources for homeowners who want to learn about SIPs, where they are used in cold climates, and considerations for Alaska.