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Year-round in a yurt

June 1st, 2014 / By: / Projects

Design meets New Zealand building code standards.

Yurts have been around for more than 3,000 years, yet they have a very modern appeal. The natural dwelling of the nomadic peoples of Central Asia, the circular, domed structure is a light-filled and airy living space. In Mongolia, the word is ger, which, translated into English, means “home.”

Origin Tents Ltd., in Motueka, New Zealand, has been making yurts for more than a decade, for camping, park buildings, summer residences, retreats and other uses that require temporary but stable structures. Recently the company developed a design for a yurt that is a permanent dwelling—taking yurts to a new level for simple, economical and environmentally friendly living. The design met New Zealand’s thermal efficiency standards and won an Award of Excellence from the Industrial Fabrics Association International (IFAI) in 2013.

“The impetus for the design came when a client, who had seen gers in Mongolia, approached us to build a yurt that their family could live in year round,” says Rowan Boot, Origin Tents co-owner and co-director. “That meant it would need to comply with New Zealand building codes, something that our other yurts don’t do. The structure also had to be suitable for connecting to service utilities like electricity.”

Up to this point, permanent dwellings had not been Origin Tents’ bailiwick. Rowan Boot began his career as a general tailor and tent maker. He made teepees and other types of historical tents from around the world for festivals and events, and founded Origin Tents in 2000. In 2010, Boot and Monique Patterson, co-owner and co-director, expanded Origin Tents into a full-fledged commercial canvas business.

Meeting building codes

Boot sees tents as a form of architecture, and he and Patterson were intrigued by the challenge their client presented. They consulted with a compliance professional to understand the different clauses in the building code that needed to be addressed to construct a
permanent yurt. The code detailed standards for structure, durability, external moisture, internal moisture and thermal efficiency.

Ultimately, the Origin Tents team hired a structural engineer and an architect to provide detailed drawings from which to work. Origin Tents designed and built the entire yurt—the internal frame, rafters, supporting lattice work and the fabric covering. All structural components were approved by the structural engineer, satisfying that clause of the building code.

The frame, comprised of stress-rated timber, was the first thing that went up when construction started. The rafters that make up the frame come together in a hub at the top center. That hub has to be strong but lightweight. “Designing the hub was the most exacting piece of what we wanted to achieve,” says Boot. “We had to make sure the components were the right size.”

At the center of the hub is a skylight: a clear dome that can be open to the sky or closed with a screw mechanism.

The roof membrane is also a structural component. It is secured with a series of tie-down points on the roof perimeter that are tied to the foundation. The fabric covering is tied onto the frame.

Beating the weather

Designing the proper outer covering with the durability to protect against the elements year-round was a key part of the construction. The walls of the yurt are 12-oz. poly cotton canvas, and the roof is covered with 670 PVC to provide a watertight membrane. The entire roof area is hot-air welded, and all the windows and awnings over the doors have generous overlaps to ensure external moisture cannot seep through.

Mitigating for internal moisture proved to be a bigger challenge. The layers are lined with Bubble Wrap® beneath the PVC cover and wool batting insulation between that and a cotton lining, which generally provides suitable protection. However, Boot and his team realized they needed more. “We could see moisture was getting inside the insulation but we couldn’t tell why,” says Boot. “We determined that internal air was condensing on the underside of the PVC roof because it was more humid inside.”

The Origin team addressed the condensation with a vapor-control barrier between the cotton lining and the wool batting insulation. This air barrier stops air cycles within the insulation, preventing condensation and moisture. Ventilation is also provided with windows that open and the skylight, which can also be opened.

Complying with New Zealand’s stringent thermal efficiency standards was the toughest challenge. “The building code in New Zealand requires double-glazed windows for permanent buildings,” says Boot. “We had to prove that we met those same standards for the vinyl windows we used.”

His crew installed over-shutters over the clear vinyl windows that are insulated with a Bubble Wrap that features an aluminum foil on both sides of a closed air cell that rates to R1.8. The wool batting insulation on the walls rates to R2.6 and on the ceiling to R3.2. All of these elements meet the timber-frame house R-value requirements for the district in which the yurt was built. In addition, the skylight is twin-layer acrylic. The completed home is eight meters in diameter, or 50 square meters, and is wired and plumbed conventionally.

Custom comfort

Each yurt can be customized for the client. A few of the options include adding a fireplace, and custom colors for the fabric covering and windows. Ensuring that the home is sited in its environment properly is also an important consideration. “We take care to customize the yurt to the site where we are building to take advantage of the views and light,” says Boot. Homes range from seven to nine meters in diameter, and the cost ranges from 30 to 50 thousand New Zealand dollars. From order to supply, it takes six to eight weeks to build a permanent yurt. Construction time on-site is just three to four days once the floor is installed—a standard timber structure with tongue-and-groove timber floorboards.

Maintenance of the yurt is fairly simple. The outer fabrics need to be replaced after about 10 years. The acrylic layer on the PVC roof has to be replaced every five to seven years due to the harsh effects of the sun. The frame components can last 50 years or longer.

Currently, all of Origin Tents’ work is in New Zealand, although they have exported one yurt to Chile. For the future, they see Australia as a potential market for these structures.

Julie Swiler is a freelance writer, editor and publicist in St. Paul, Minn.

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