Thanks to everyone who has pushed me for an update on the carbon neutral prototype house project. I’ve had my hands full and blogging just hasn’t risen to the top of the list. Stay tuned because I have six months of great research results on a number of fronts including compressed earth block floors and walls, site made earthplasters, and a simple purchased clay and sand earth plaster.

What everyone asks first, however, is “when are you gonna be done”? Let’s put that baby to bed once and for all: we’re done. We’ve received our Certificate of Occupancy from the city and are jumping through a few hoops for the bank (don’t get me started, gawd!). Our test family, Jeff/Jeanine/Jackson (JJJ), are moving in upstairs next week. We’re looking for someone to live in the downstairs apartment, and the Nauhaus think tank/office/lab will be moved to the downstairs office.

So from a real estate, taxes, and bank perspective, we’re done. However, the point of this research project wasn’t just to build a house, but to create a living lab and opportunity for study, so there is still lots of work that we’ll do. High on the list will be to complete the final blower door test to see if we will receive Passive House certification. In the next month or two, we’ll be completing a collaboration with Tom Rioux of Earthpaint to test a number of finish solutions for the earthen materials in the building. This is exciting work because in the end we’ll be able to specify commericially available products from Earthpaint to finish and seal compressed earth blocks and earthen plasters.

If you want to help us with our ongoing research, we still need support to realize our:

– Clarke

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.

A quadruple pane window from Serious installed in a hempcrete wall in the Nauhaus Prototype

Well, we finally got the windows and doors installed. Okay, let me vent for a sec: prototypes are a bitch. We had to do a lot of head scratching and trial and error to figure out the best way to insure airtightness in our installation. The hempcrete is awesome, but it create its own set of challenges, especially since our truly wonderful Serious windows aren’t really designed to be installed in the middle of thick walls. (Serious is a partner with us on this project and we’re working with them to make things easier when you decide to replicate what we’re doing.)

First, let’s sing the praises of these windows. Though a number of German companies make windows in this category, Serious Materials is the only US company that can meet the required specs for a Passive House. All window and door units on the project have fiberglass frames and quadruple pane glazing. Southern glazing has a center of glass insulation value of R-7 with an impressive solar heat gain coefficient (the percentage of solar heat that passes through the glass, 1.0 would be 100%) of about 0.7. This allows for heat gain from the low southern winter sun, a strategy integral to the Passive House integrated design system.

North, east, and west glazings weigh in at an amazing center of glass rating of R-11, a rating equal to the fiberglass insulation in some conventional stick frame walls! This is compared to R-2 for a typical double pane window found on most US projects. Unlike the heavier European windows, Serious reaches this performance level with two pieces of glass and two pieces of plastic allowing for a thinner profile more like conventional windows typically available in the US.

Why all the fuss? Well, I’ll tell you. In a Passive House in our climate region, walls need to be about R-40.  Sticking an R-2 hole in an R-40 wall just doesn’t make sense.  In a Passive House, the idea is to spend money on passive elements, extra insulation and really good windows for example, that don’t require energy inputs to do their job once installed, unlike heating, cooling, and ventilation equipment. In the right configuration, these passive elements combine to allow for a much simpler and less expensive mechanical system, thus saving money in construction and afterwards with much lower energy bills.

Anyway, we’ve got video footage that we’ll eventually compile into a bunch of great educational how-to videos on the ins and outs of all this nifty construction detailing. If anyone out there is getting antsy for the goods, getting us a grant to fund collation of the documentation footage would really speed things up. Until then, wet your chops on these few photos:

Here you see our custom plastic lumber sill piece with groove for backer rod and space for spray foam, the edge of the bituthane sill pan (green stuff), and the poured in place concrete exterior sill.

All windows had to be pre-drilled through the fiberglass frames...

...then screwed to the stud framing in the middle of the hempcrete wall.

Jeff puts his engineering degree to work installing a backer rod as part of a multi-step installation process to insure maximum airtightness

The plastic lumber sills were filled with foam after installation through a series of pre-drilled holes...ingenious!

Southwest view showing windows installed. Doesn't look like any big deal, does it?

Master carpenter and benevolent genius Tim working on a door. Installing the doors was a whole different story...don't get me started!

Anyway, we’re behind on the blogging and I surely don’t have time to bring things up to date right this minute. The quick synopsis is that the hempcrete installation is complete (yeah, baby!) and we’re moving into “Phase II” of the build in which the design team will be on site a lot more working with interns. Right now we have four great interns, Christopher, Shannon, Francoise, and Bertrand. (Fun fact: F&B rode their bikes from Montreal by way of Florida and Texas!? Those crazy Canucks.)

Here are a few picks. I hope to get more up soon….or convince Jen to quit school.

Southwest view of finished hempcrete installation. Looks a lot like rammed earth, eh?

Shannon, Bertrand, and Christopher.

Francois working on a mortise and tenon roof bracket.

Tim teaching joinery as part of bracket production.

Tim and Bertrand installing the front porch deck framing.

Shannon working on the earth plaster test wall.

Jeff raising a window header in a hempcrete wall... it's easier than it sounds.

Jeff starting air tight installation of a window frame.

Christopher predrilling a window frame.

Tim giving a tour to a class from Warren Wilson College.

Bert dreaming of poutine.

Click here to view the entire Nauhaus Prototype Construction Chronology.

If you’re interested in volunteering for the Nauhaus Prototype Project, please contact Billy.

Nauhaus Prototype Project from jennifer bennett on Vimeo.

If you’re interested in volunteering for the Nauhaus Prototype Project, please contact Billy.

Click here to view the entire Nauhaus Prototype Construction Chronology.

Current View of Southeast

Current View of Southwest

Hemp Stacked and Waiting

The Trusty Mixer

Adam is the fastest Hemcrete installer in the West!

Support for Upper Forms over CMU Wall

Closeup of Form Attachment

Scaffolding

The forms are built up almost ot the overhangs, and are stuffed by hand.

Completed Window Opening

Thermally broken mounting bracket for roof supports. The pink is foam insulation.

Closeup of Hemcrete in Form

A combination of custom and pre-made forms is used on the 2nd floor.

If you’re interested in volunteering for the Nauhaus Prototype Project, please contact Billy.

Click here to view the entire Nauhaus Prototype Construction Chronology.

Wall with Custom Hemcrete Forms

Wall after Hemcrete Forms are Removed

Serious Materials Windows Have Arrived

Serious Materials Windows Waiting for Installation

Head and Jamb of Hemcrete Window Opening

Jamb and Sill of Hemcrete Window Opening

Sustainably Harvested Hemlock Fascia

Closeup of Future Patio Connection at West Wall

Nauhaus Prototype as of December 31, 2009

If you’re interested in volunteering for the Nauhaus Prototype Project, please contact Billy.

Click here to view the entire Nauhaus Prototype Construction Chronology.

Ian Snider and Jeff Buscher

House with forms on the South side.

Elisha measures.

Shutter being attached.

Elisha

Sarah tamps the Hemcrete.

Hemcrete in Mixer

Nauhaus Building Systems mixes Hemcrete.

Shutters line the interior South wall.

Interior of West and North walls without forms.

Electrical Box in Hemcrete

Click here to view the entire Nauhaus Prototype Construction Chronology.

Buckets of Hemp

Custom forms on Completed Framing

Exterior Bracing at Plywood Forms

Custom window forms were built so that the jambs could flare out and let in more light.

Horizontal form supports are painted orange, as they will be removed after the the Hemcrete is packed in.

Matt pours hemp into the mixer.

Nauhaus Team and Volunteers Installing Hemcrete

A volunteer tamps down Hemcrete around the studs to ensure a tight seal.

Sarah tamps Hemcrete. At this point, the forms are 4' high because the first 2' layer is completed.

Today, as the Hemcrete installation continued, Amy Musser of Vandemusser Design came out to give us a LEED consultation.  The Prototype is still on track to receive LEED Platinum certification.

Amy Musser, Luly Gonzalez and Chris Cashman discuss LEED.