Category Archives: Humidity

Nauhaus Prototype Gets Plastered

Exterior and interior plastering is underway on the carbon neutral Nauhaus prototype.

The interior surface of the hempcrete walls has a base coat of earthen plaster consisting of sub-soil harvested from the construction site and mixed with sand and water. The mix was chosen after testing sixteen different compositions, a process spearheaded by intern Shannon Levenson. Earth plaster serves the Nauhaus prototype mission because it requires almost no energy to make or transport, and therefore has very little carbon emissions associated with it. In addition, earth plastering is fairly easy to learn, requires few tools, and is instantly gratifying, both because it’s beautiful at any skill level and very similar to playing with mud pies, a therapeutic experience that many adults realize they have been neglecting for too long. Whatever the reason, the earth plastering process attracted volunteers and interns like flies to…well, compost.

The exterior wall surface has been covered with a base coat of lime-based plaster supplied by Lime Technology as part of the hempcrete wall system. Both interior and exterior plasters were applied directly to the hempcrete which proved to be an excellent plaster substrate. Fiberglass mesh, similar to mesh drywall tape, were embedded in plaster over any joints or cracks in the hempcrete. Together these plasters over hempcrete create a vapor permeable wall system, sometimes called a “breathable wall”. The idea is to create a wall that is open to taking on and giving off water vapor in response to humidity levels in the air inside or outside the building.

We believe vapor permeable walls will last much longer and help create better indoor air quality than cavity wall systems that dominate US residential construction. As any builder will tell you, it’s pretty much impossible to keep water out of walls. Permeable walls are designed with the idea that it’s okay if some water gets in as long as it can get out just as easily and won’t cause any damage in the process.

Gravel and Vapor Barrier

Today, another 20 mil. vapor barrier was spread over gravel, in preparation for the insulation and concrete slab.

Click here to view the entire Nauhaus Prototype Construction Chronology.

Drain and Insulation with Gravel
Drain and Insulation with Gravel
Finished Gravel
Finished Gravel

Vapor Barrier at CMU
Vapor Barrier at CMU
All penetrations through the vapor barrier are carefully sealed.
All penetrations through the vapor barrier are carefully sealed.

Finished Vapor Barrier
Finished Vapor Barrier



Vapor Barrier Under Footers

Today a 20 mil. vapor barrier was laid in the trenches.  The concrete footers will be poured on top.   Radon pipes were installed for future venting if necessary, and greywater pipes were stubbed-out in hopes that one day a legal greywater system will be possible.

Click here to view the entire Nauhaus Prototype Construction Chronology.

View of Completed Vapor Barrier from Southwest
View of Completed Vapor Barrier from Southwest

tim vapor barrier
Tim Callahan
Stubbed-out Radon and Greywater Pipes
Stubbed-out Radon and Greywater Pipes