How to build a Passive House off-grid, and without foam

The <a href="http://inhabitat.com/tag/passive-house/">Passive House</a> Institute is known to have one of the strictest energy-efficient building standards in the world. What does it take to build your own Passive House, and how can you do it with healthy, high-performance materials? This is the second of a <a href="http://inhabitat.com/tag/martak-passive-house/"> three-part series</a> on the challenge of building a certified Passive House without foam or other harmful materials. The challenges are numerous—from sourcing materials to making it as airtight as possible, and keeping an unseasoned team (and myself) on task. For <a href="http://inhabitat.com/green-building-labels-101-an-inhabitat-guide-to-third%C2%AD-party-environmental-certifications/">healthy materials</a>, simple substitutes for traditional products are not only typically easy but also cost effective. Take a look at what it takes to build a Passive House in the Colorado Rockies.

In the <a href="http://inhabitat.com/how-to-design-a-passive-house-off-grid-and-without-foam/">last article, </a>we started to build the house even though the energy model was not completed. The modeling took some dips and turns as we progressed (more on that later) but that didn't not slow us down. We were able to <a href="http://inhabitat.com/boeing-plant-hidden-beneath-a-fake-neighborhood-tapped-as-salvaged-lumber-source/">deconstruct </a>the original shop and keep the tire wall foundation, and reuse most of the materials to boot.

Carefully keeping the surrounding Ponderosa Pines safe, which provide critical shading in the summer, we dug out a foundation stem wall and crawl space, a design that is critical to the foamless flooring insulation system. Not only does this minimize the concrete use but 20 percent of the cement was replaced with <a href="http://inhabitat.com/fly-ash-pollution-could-be-used-as-a-construction-material/">fly ash</a>.

The framing is very conventional: 2x4 studs with I-joists spanning the floor and roof. For air sealing we primarily used plywood and tape.

Much of the airtight layer is simply plywood or OSB which has seams that are taped using <a href="http://foursevenfive.com/manufacturers/pro-clima/">Pro Clima</a> Vana, which is also non-toxic. To do air sealing right you have to find religion about making sure that every place where two building elements come together is properly sealed well before they are covered.

At the foundation we applied a plywood "seat" for the I-joist to sit on and a similar detail happened at the wall to ceiling connection. Because the walls will be very well insulated, we used vapor open materials for airtightness so moisture does not build up in the wall over time.

The air barrier is closer to the living space so water will not condense on it if it gets really cold outside. The ceiling and north wall are wrapped with Intello, a "smart" membrane that changes its vapor profile depending on the relative humidity.

Why is air tightness such a big deal? Passive House requires a leakage test of .60 ACH at 50 Pascals or less because leakage is a fundamental way a building loses energy and to introduce opportunities for mold and rot-inducing moisture in a wall.

Now that the building's airtight layer is done, we can test it before we install windows, insulation, and all the other stuff that can cover a potential problem. We hit a respectable .45 ACH at 50 Pascals, or roughly the equivalent of 8 square inches of total opening in the entire building envelope.

Now that we know we are on the right track, it's time to make the insulation layer. The primary insulation material is <a href="http://www.applegateinsulation.com/Product-Info/Insulation-Products/Loose-Fill-Insulation/default.aspx">Applegate cellulose</a>, sandwiched with Roxul mineral wool batt on the inside and <a href="http://www.roxul.com/products/commercial/products/roxul+drainboard">drainboard </a>on the exterior. We start with<a href="http://www.greenbuildingadvisor.com/blogs/dept/musings/all-about-larsen-trusses"> Larsen Trusses</a>, basically a ladder like frame made from 2x3 supported by plywood scraps and wrapped in weed fabric to hold the insulation.

The Larson Trusses are screwed to the exterior wall to make large bays, and a 2.3/8" layer of drainboard is then screwed to that.

After not finding a competent contractor to insulate the bays with cellulose I purchase a machine and get dirty, learning the ins and outs of properly filling a 24" wall cavity so the insulation will not settle over time. Overall we installed 1100 25 lbs bags of the stuff, which is just about an entire semi-load. The best part is the insulation is all recycled from nearby Denver and produced only 100 miles south. The mineral wool board on the other hand had to be specially made and shipped from a factory in Canada.

The Intus windows came from Lithuania, in their own container. While less than ideal, the cost and performance are untouched by any American window manufacturer. They swing inwards and can be placed so the exterior frame can be over insulated to reduce heat loss through the frame. The PVC windows also are the largest compromise by far from my unhealthy materials list because it <a href="http://www.healthybuilding.net/news/2007/03/09/usgbc-pvc-is-not-a-healthy-building-material"> is highly toxic </a>to manufacture and very hard to recycle.

Another vital Passive House technology is the Heat Recovery Ventilator. This technology uses two fans, one to extract bad air, and one to provide fresh air. The unit I selected was the first in the US from a Czech Republic manufacture <a href="http://www.airpohoda.eu/en">Air Pohoda</a>. It uses an a stingy 32 watts in regular mode (important for being off grid) and is over 90% effective at reclaiming waste heat.

A heat exchanger keeps the energy in the building, and when hooked up to an earth tube, the house can be naturally cooled in the summer.

I also install a Phase Change material <a href="http://www.phasechange.com/index.php/en/">Bio PCM </a>which uses a soy wax to store or release excess solar heat at 74 degrees Fahrenheit.

In the meantime, the energy model seems to go haywire when new climate data is entered. I found some interesting issues when I went sleuthing for what happened. We are also now ready to put up finishes: siding, drywall, finish plumbing and electrical. The punch list never seems to end.

In the last installment of my three-part series, I'll discover whether it's possible to stay in a house in Colorado with no working heat in winter, and after doing the Passive House Planning Package software modeling for myself, I get a huge surprise.

We do the final blower door test with fingers crossed, and I decide to submit to the<a href="http://www.passivehouseacademy.com/"> Passive House Academy</a> for the German certification and forgo the <a href="http://www.phius.org/home-page">Passive House Institute US</a> certification. Ironically, I was the<a href="http://inhabitat.com/passivhaus-institute-ends-relationship-with-passive-house-institute-us/"> first to report on the US-German split</a> in 2011, and that news came to be a very personal journey.

Some of the low-impact products: <a href="https://foursevenfive.com/product/intello-plus/">Intello Membrane</a> made from 100 percent recyclable nylon, <a href="https://foursevenfive.com/product/eco-coll/">Eco Coll</a> natural latex caulk, <a href="http://www.ecobondadhesives.com/store/index.php/specials/eco-bond-multi-purpose-mp25.html">Eco Bond </a>non-toxic caulk, <a href="http://foursevenfive.com/product/tescon-vana/">Tescon Vana</a> air sealing tape zero VOC solid acrylic, ABS Pipe to replace PVC, <a href="http://www.roxul.com/products/commercial/products/roxul+drainboard">Roxul Drainboard</a> reclaimed steel slag and rock, <a href="http://www.applegateinsulation.com/Product-Info/Insulation-Products/Loose-Fill-Insulation/default.aspx">Applegate Cellulose </a>locally-sourced and made from waste paper, <a href="https://us.fsc.org/">FSC certified</a> plywood and lumber.

We use organic felt paper and twine under the steel roof.