Free Renewable Energy Not Always Free

Being eco-friendly may be admirable, but it comes with a price, and it is not always as crystal-clear as one believes.

We rely heavily on non-grid energy, including wind and solar power.  However, renewal energy sources such as ours require energy storage, and, specifically, battery storage.  While there are advanced battery technologies on the market (e.g. batteries for hybrid vehicles), as well as large wet-cell storage batteries (such as those in forklifts and indoor industrial cleaning equipment), the most prevalent, and therefore, the lowest-priced units are conventional deep-cycle marine 12-volt batteries.  These typically cost from $80 to $200, with only modest storage and cranking amperage.

The primary advantage of marine batteries over vehicle batteries is their capacity to be discharged to low levels and recharged often.  However, “often” is subjective, with most of the commercially available units being rated for a few hundred charging cycles, at most.  These batteries also do not like to be frozen, but really detest excessive heat.

In order to supply minimal energy, such as the energy to light two compact fluorescent bulbs four hours each day and a small bar refrigerator (drawing 90 watts, with a surge of 800 watts), you will consume 2,280 (2.3 kw) watts each day.  Now consider that a small solar panel produces 13-18 watts (some of the single panel retail units produce 30w) under optimal conditions.  In northern latitudes, hours of summer daylight average 15 hours, but typically generate only about 60% of that in sunlight sufficient to “max out” the solar panel.  With three panels, you will produce 405 watts – less than 20% of what you need.  A small wind turbine may produce 40% of what you need, if you live in an environment where the wind is very frequent, and of sufficient strength to power the turbine. Typically, the marine batteries attached to your collectors are rated for 800-1000 CCA.  Obviously, unless you expand your generation and/or storage network, you will need to use a charging system on the batteries.

Because each of the batteries is being discharged the equivalent of 100%every eight hours, you will require a battery array of at least three batteries, just to produce your daily minimum energy requirement.  Ultimately, most of us will require electricity for television or sound equipment, charging cell phones and laptops, power for small fans, and so on. With minimal energy, though, your three-battery array will be fully discharged and recharged 100 times from June to September.  That is the normal lifespan of the battery!

This year, we experienced near-record heat and sunlight throughout our summer.  While that is great for our solar panels, heat is more damaging to the batteries than cold, and reduces their ability to be recharged (and hold a charge) significantly.

We used an eight-battery package.  However, almost weekly, we needed to refill the cells, as the electrolytic acid evaporated.  The sunlight did its damage, too, destroying one battery.  Of the eight, only one battery now holds a significant charge, even though I de-sulphated the batteries regularly.  Five of the batteries were three years old or less, with the other three being four years old.  Seven batteries will need to be replaced.

At a cost of $90 per battery, our outlay will be $630, plus taxes.  We used nearly $100 of generator fuel to supplement our renewable energy supply.  In four months, our lighting costs will be $700-800, factoring in the wear and tear on equipment.

Now, we have batteries that need to be recycled and spent fuel that polluted the air.  If we had relied on our hydro-electric grid for energy, at a cost of $0.08 per kwh, we would have spent less than $130!  Did we really do the environment and our pocketbook a favour?

Thermal Bridging Solution for Yurts

At the point where the roof rafters of a yurt meet the upright walls (particularly in a solid wall yurt design), there will be thermal bridging.  This leads to condensation and cold spots in cooler months.  Yurt design generally fails to compensate for this loss of heat.

In the solid wall yurt that I constructed, even though I used foil backed insulation and bubble foil insulation to minimize the extent of heat transfer, the results last year were largely inadequate.  However, this year, I believe I have found the solution, and it is, in part, due to the supplementary restraint system that I incorporated in the design.

In prior articles, I discussed how I had installed a dome tarpaulin that overhung the walls by about eight inches.  This reduced air infiltration during wind, allowed for a greater ability to shed “horizontal” rain, protected against pest intrusion, and allowed us to create a small overhang above the windows. 

I also installed another feature: ratchet strap tie downs around the upper perimeter of the walls.  While the ropes that tether the roof tarpaulin to the unit generally are adequate, and the sole restraint system in many conventional designs, the ratchet straps can be adjusted around the circumference to further resist the parachute tug of high winds.  At a cost of less than $40 for ninety feet of strapping, it is an inexpensive solution.  That strapping also allows me to install a flexible rain gutter (see prior articles).  However, its greatest benefit is in the ability that it provides to me to resolve the thermal bridging problem in the yurt.

Thermal bridging occurs, quite simply, where a harder surface that transmits hot or cold easily is exposed to the elements and to a conflicting heating or cooling source.  Think of that metal counter top, and how cold it seems to the touch in winter, how hot in summer.  Wood, although offering less transfer capacity, still acts as a bridge.  In houses, R-factor of insulating walls is lowered, if the studs meet the outside and inside walls with no insulative materials between them.  The same happens in the yurt.

To resolve the thermal dilemma, I cut pieces of two-foot wide by one inch thick rigid polystyrene insulation into five-inch lengths.  Sliding these under the ratchet strapping and to the apex of the walls, all around the circumference of the yurt, I provided an R-5 insulation barrier between the top plate of the walls and rafter joints and the outside air.

Although, to date, temperatures have remained moderate by late autumn standards in the region, I have experienced no condensation in these areas, where I did so last year when the temperature neared freezing.  Although an infrared thermometer shows a five-degree difference in temperatures at the bridge point versus the rest of the wall area, this differential is insignificant.  Accordingly, I completed installation of similar strips of rigid insulation along the bottom perimeter of the yurt, where wall meets floor.

Yurt Popular, Even With Flies

Flies: not the most attractive topic. But flies are an everyday part of our summer lives, and, in our yurt, we have discovered that flies can be particularly bothersome. The design of a yurt lends itself well to being a haven for these pests. The relatively loose fit of the tarpaulins allows these nuisances to squeeze themselves through crevices and cracks, while the permeability of the structure enables odours to waft outward. Combine these two factors with the tendency of the roof tarpaulin to trap the sun’s heat, and yurts become playgrounds for flying pests.
Last autumn, for example, I removed a portion of the dome insulation to install additional snow load braces, and found hundreds of dormant flies embedded in the top side of the fibreglass insulation layer. While part of the problem may have been that the eggs pre-existed in the insulation package, recent hot days have stimulated an invasion of black and bluebottle flies.
An additional contributor to the attraction of our yurt for flying insects is the presence of our grey water tanks and compost holding tank near the home. Whenever we drain or flush these systems, flies are drawn to the site.
The round design of the yurt, as well, means that there is less air turbulence, on windy or calm and hot days. This relative tranquility allows flies to gather and reproduce.
We have implemented and tested a variety of solutions. The conventional insect trap is a general failure, for flies, mosquitoes and wasps. Unfortunately, it does a terrific job on moths, which we prefer to allow to thrive.
In desperation, we resorted to commercial chemical sprays, without success, while also flooding the environment with toxins. These sprays included perimeter, spot and space sprays, all equally ineffective.
We grow such plants as tansy, lemon balm, sorrel and other natural insect repellents. They do work, but only within a very limited and defined area. We would need to plant these sentinels every few inches around the home, and even vertically on our yurt walls to have any hope of winning the insect war.
Inside the yurt, we have resealed all of the joints of the foil-backed bubble insulation that lines our yurt roof. This action has been significantly successful, as the flies that do hatch in the domed area must migrate outward, rather than inward.
Our walls have been difficult to seal completely, given the way they moor to the roofline and floor. However, taping all of these joints has been successful, as well.
A third successful solution has been to open the dome vent while closing all but two of our windows, and using our ceiling fan to draw the air upward, instead of forcing it downward. We have installed a floor vent that allows cool air from beneath the deck to be drawn upward. This continual air movement keeps the flies from settling. The round interior of the yurt maximizes air movement, which the flies dislike.
The last proven solution that we have employed is to install a small fume hood over our cook unit, and bent it outside. With less odour to attract the flies, they now prefer to congregate near the outside vent.
We are experimenting with one other solution: mustard paste. In past years, I have had great success in deterring bugs and crawling pests in the garden, by obtaining mustard seed and wild mustard screenings from a local seed cleaner. When crushed and applied near plants, insects shy away from this hotfoot compound. We have obtained mustard oil (crushed form these same seeds), and have applied a spray under the lip of the roof tarp where it meets the wall, around the base of the wall tarp and around the window and door cutouts. So far, in the areas where this oil has been applied, there is a huge reduction in fly accumulation. However, we need to observe how long this spray lasts, and whether it has a detrimental effect on the fabric. We will keep you posted!

Yurt Interior Walls

One of the great benefits of the yurt design is the open room concept. The lack of walls means that air moves freely. Combined with the round yurt structure, this means that a greater efficiency in both air movement and its contingent heating efficiency result. However, modesty demands that we build our homes with a private bathroom. Even in a yurt, this means walls, and a barrier to smooth air flow. Similarly, many of us want closets and wardrobes, whether they are built as standalone units or integrated into the bed enclosure. Again, the natural flow in the yurt is interrupted by such barriers.
In our yurt, we built a six by eight foot bathroom, but left the ceiling area open. While the walls do provide impediment to air movement, the open ceiling concept means that warm, moist air is able to move out of the enclosure, and reduce heat and vapour pooling. By combining our closet space into the rear, outer edge of the bathroom, we were able to reduce the number of structural breaks.
Still, these barriers created condensation problems within the yurt. In the late fall, cooler outside air and a lack of air movement in the corner areas where wall met outside wall, a severe moisture problem resulted, with development of mould. We solved that issue by implementing several strategies.
First, we installed small 12 volt fans in these vulnerable portions of the yurt. The fans were salvaged from desktop computers, yet are sufficiently powerful to move the air away from these stagnant areas.
Next, we doubled up on the insulation factor where floor, outside wall and inside wall met, installing a one inch thick segment of polystyrene rigid insulation, extending six inches above and below the floor level.
The third change that we implemented was to install two fans along the top plates of the bathroom and closet, forcing air to move from floor to ceiling.
By moving our furniture and small items away from the outside wall, we increased air flow.
Lastly, we bored two inch holes at the base of the wall, allowing the air to move freely between the main yurt floor space and the bathroom and closet.
It is imperative, if you are choosing to build a yurt for efficiency, that you consider what makes the yurt an efficient design. Vertical air movement, allowing hot air to rise in the summer and vent at the apex of the dome, as well as moving it downward with small fans in the winter, is a significant feature of the yurt design. It is more imperative, though, that you reduce barriers to air flow in dead spaces and “corners” of the yurt. Simple layout alternatives provide this free flow of air. Where possible, consider moving walls a few inches from the outside, and tie them together in a free-standing box system, so that there is a space along the entire height of the exterior yurt wall, keeping air flowing freely. Ensure that insulation is installed properly and evenly, with no cold spots to encourage dead air and condensation.
Built properly, the yurt design is a marvellous system. Done carelessly, and it loses its structural integrity and natural efficiency.

Solid Versus Flexible Wall Yurt Systems

Yurt purists will insist adamantly that its simply is not a true yurt if it has solid walls. Yet, the original yurts, from Turkey to the Himalayas, had neither tarpaulin skins or space-age bubble insulation and glass-domed vents. Yurts, indeed, are more about simplicity and function than any purist concept of how they should be designed, and from what materials.
It is true that the lattice/tarpaulin skin systems employed by manufacturers from Yurtco to Colorado Yurts have aesthetic appeal. Their flexible framing, bubble insulation and heavy-duty pvc tarps allow for an intimacy with the surrounding environment that a conventional house or cabin does not. The sound of rain on the exterior skins is magical, and the thick plastic windows create an aura of living in a tent. Even in relatively stiff winds, these yurts hold steady, yet react to the breezes. Yet, these same benefits also can be drawbacks.
Since windows are nothing more than thick, clear poly plastic, they transmit heat and cold easily. To cut down on sun infiltration, the exterior skin must be zipped shut. Similarly, in winter, those same windows almost always are zipped closed, creating a claustrophobic, tomb-like atmosphere. If the window is improperly installed and allowed to vibrate or shake, the plastic quickly breaks down, and, in a matter of a few years, the window must be replaced when it cracks.
The light lattice framing does withstand winds of 70-90 kph, but a wind/snow load supplementary support system must be installed in high wind/high snow regions. Of particular concern for many is the loose fit of the yurt wall skins at the base of these units. While tight enough to hold back the elements, many yurts with lattice wall design, according to owners, allow small rodents such as voles to work their way into the building during the colder months.
Due to the thinness of the exterior walls, R-factor levels for insulation are minimal, with only a few centimetres of space-age bubble insulation protecting against the elements.
A reasonable fear that some people have expressed is that the light construction is a poor impediment to a hungry bear, who may smell food through the fragile skeleton of the yurt. Whether the fear has ever materialized is irrelevant, as the fear may still exist even where the risk is minimal.
On the other hand, solid-wall yurts offer a great many advantages. Few bears, badgers or raccoons have the tenacity to force their way through 7/16 inch of wood, plus framing, making the structure seem considerably safer from these predators than flexible-wall yurts.
With the exterior tarpaulin covering those walls, wind and air infiltration is minimal. The framing allows for two to three times the insulative capacity than lattice walls.
Wind endurance is significantly greater in a properly designed solid wall yurt, as well. Using the interlocking top and bottom plate segments that has been created for these units, the structures have endured winds of over 115kph, without any sign of stress or strain. In one instance, a healthy tree, sixteen inches in diameter, was sheared off by the wind not more than forty yards from the yurt, yet the yurt suffered absolutely no ill effects from the wind force.
Window and door installation is easier and less expensive in solid wall yurts. Because of their framing, these buildings can be constructed using standard windows (double or triple pane) and doors, allowing for reduced cost, energy saving and better light infiltration. It is also a lot more difficult for a raccoon to claw through a pvc & glass window than a plastic one!
Along with the advantages of solid wall construction, these hybrid yurts maintain the tarpaulin roof structure, along with added truss strength to withstand heavier snow loads. The tarpaulin skin allows for the same magical enjoyment of a rainfall on the tent-like roof, the same intimacy with the outside environment and the same open atmosphere as more “traditional” yurt systems.
Yurt purists may decry the bastardization of their beloved structures, but they will have a hard time denying the advantages of solid-wall over flexible-wall yurts.

The Romance Of Yurt Life, Wildlife Included

When you choose to live with nature in a yurt, it is a marriage: you accept the good with the bad. But even the bad can be great in the springtime! We have only been back in the yurt for a few weeks now, but our encounters with the wildlife have been nothing short of enthralling and amusing.
Last autumn, we closed out our season in the backwoods with a visit from a family of four raccoons, who systematically destroyed every bird feeder we had put up while they scavenged for the last meals of the season. A couple of squirrels determinedly decided to winter in the insulation under the platform deck of the yurt, as well, but we were willing to tolerate them for the four bitter months that we were away from our home.
As spring broke this year, though, we found just what damage a couple of active nut-eaters can do to insulation! Our raccoons have returned, as well. What is unusual is that the family of four remains together, with no new litter of kits in evidence. They announced their return by using their can-opener teeth to puncture a Coleman cooler that I had left outside. For dessert, they gnawed their way into a plastic gas canister, filled with mixed fuel for my chainsaw, and dragged the leaking container across the grass. Given their “finger” dexterity, I am glad I did not leave a barbeque lighter around!
Thirty miles north of us, Hecla Island, in Lake Winnipeg, is the summer home of turkey vultures and a few bald eagles. Rarely has either been spotted away from that area, yet, just as the snow melted from our meadow, a bald eagle pursued a mouse, and landed in the field to finish his lunch. It is just one example of the changing patterns of wildlife in the area. We have two mallard couples nesting in the creek bed not fifty yards from the yurt, sand hill cranes that have relocated their annual nesting area from the adjacent farmland to our small meadow, a grouse sitting on eggs under a three-foot high spruce in a clearing only paces from our home and coyotes that have decided that it is safe to howl, nightly, thirty feet away from where we sleep.
Late in the winter, I encountered a lone black wolf (probably from the Hecla pack) that obviously had strayed form its traditional range twenty-five miles north of us.
My wife is less happy with our annual migrant bear, who has, each spring and fall, travelled along our old riverbed with her latest cub. Two weeks ago, she came up to our doorstep with her cub, demolished a sealed garbage container and dragged one of the bags two hundred yards through our garden before tearing into it. As bold as that action was, she showed that she is less wary of human contact than ever, when she returned, during a rainstorm, to the yurt and rooted around the deck. In the morning, her huge paw prints in the wet clay where I had been excavating provided more than ample evidence of her visit.
Fortunately, our resident skunks and badger have not opted to become emboldened, and move in under the yurt platform!
More humorous that dangerous are the romantic interjections of local wildlife. Our ducks and Canada geese have almost finished their courting, calling, dancing and preening, while the frogs continue to be in great serenading voice. There is nothing quite so mood-destroying, though, as the cooing, gurgling and raucous clucking of crows in love. Their grating calls have all the appeal of a screaming baby. On the other hand, who can turn a deaf ear to the Buddy Rich drumming of a male ruffed grouse at 3:00 a.m?
The best of the strutting males though, has to be one of the many sapsuckers in the woods. For six years, he has chosen to drum his mating song not in nearby trees, but on any metal that he can find. Six years ago, it was my old Cockshutt tractor. Then, he found a better sound with an empty 45-gallon steel drum. Last year, it was the tin bonnet on my old camper. This morning, though, he reached the apex of quality music when he found that the roof of our new Prius provided the melody that he wanted.
It is there that I draw the line at passive interaction with nature. Tomorrow morning, I expect to join him with a few well-directed tennis balls to divert his attention from his new $30,000 toy! I expect, however, that, with the abundance of empty containers and old iron in the yard, it will be only moments before our rock-star drummer finds a new beat with which to lure his mate.

Inexpensive Yurt Flooring Solution

In keeping with the minimal philosophy of living in a yurt, the ideal design will employ a minimum of materials, be as “green” as possible and will be both sustainable and durable.
In our yurt, we have chosen a very inexpensive, basic design and material for our flooring. There are several reasons for this.
Firstly, cost is a factor in the decision as to the type of flooring to use. We opted for materials with a cost of less than $0.45 per square foot, plus $0.10 per square foot for finishes.
Secondly, we wanted to ensure that the frequent traffic directly from outdoors to indoors did not track in excess dirt. Carpeting would have trapped that dirt.
Thirdly, the location of the yurt in a wooded area would have attracted insects such as ants. By constructing flooring with a hard surface, we eliminated nesting sites for those insects.
Fourthly, we wanted a floor that would remain cool in the summer and able to adapt to winter conditions. With the hard surface, we were able to lay down area carpets that we already owned in strategic locations, while keeping bare floor at entrances and frequently used work areas, such as the kitchen areas and washroom.
Lastly, we wanted to minimize weight of the flooring, since we built the yurt on pads and posts, rasther than embedding pillars into the ground.
To accomplish all four goals, we used ¾ inch oriented strand board as sub floor material, with 1/8 inch good one side plywood laid at a ninety degree angles to the subfloor as the main floor. The plywood was screwed to the underlay using three quarter inch wood screws with threads the full length of the screw. The use of full-length threads is essential, so that the screws can be countersunk into the thin plywood.
Lastly, we used a clear varnish to coat the surface of the flooring, making sure to pay special attention to the high traffic areas.
Since installing this flooring, we have found that it works remarkably well, and shows a sheen and grain similar to good-quality hardwood or laminate flooring, at one quarter of the cost.
However, some problems have arisen. On occasion, we stored 20 pound propane tanks on the floor, and, with changing temperatures, the tanks attracted condensation. This condensation accumulated in a ring on the floor. To remove it, we lightly scoured the area with a Javex and water mix, with modest success. The only other problem has been a slight separation, due to the thinness of the material, in spots where insufficient screws were used.
This flooring has answered all five of our criteria for the design, and is recommended for anyone contemplating an inexpensive flooring alternative, whether in a yurt or cabin.

Yurt Perimeter Drainage Solves Humidity Problems

Perimeter drainage
Spring has proven to be a real test for our yurt. To close out the late fall and early winter, we experienced exceptionally unusual rainfall and early snowfall. Because we have built our yurt on the slope of a hill, the deck on which the yurt rests is at ground level at the rear, and fifty-four inches off the ground in the front. This permits good air flow, but demanded that we hoard the perimeter to block cold air infiltration. Unfortunately, the hoarding also trapped humidity, and we experienced numerous condensation issues throughout November and the first week of December.
The interior of the yurt is lined with foil-backed bubble insulation, with all joints taped. This makes for a very air-tight unit, but any moisture inside is trapped, as well. Cooking, showering and even everyday living contributes to the high humidity. We experimented with a number of options to reduce this wet air, with limited success.
The major problem was that, because it was winter, we needed to seal and insulate our rooftop vent. This creates a dome where the heat rises and remains somewhat trapped at the apex. Although the yurt is quite warm and well insulated, there are many partial thermal bridges, at the headers, the window framing and even at the roof ring and rafters. As soon as we reduced interior temperature, the cooler outside air would condense humidity on the foil, which would accrue and run down the walls or drip from points of the roof.
Using a fan at the peak of the dome ameliorated the problem, to a degree. Similarly, by adding insulation between the tarp and the exterior wall framing, we were able to reduce the temperature differential. Lastly, we reduced our interior temperature by a couple of degrees and maintained that temperature day and night.
The major problem that remained was the moisture in the soil under the yurt. This spring, moisture levels have been exacerbated by heavy rainfall and a slow thaw that releases the moisture in the ice slowly.
This week, we believe we resolved that issue. By trenching around the perimeter of the yurt profile to a depth of six inches and six inches wide, we have created a mini-drainage ditch. This U-shaped trench catches the rainfall as it falls from the walls, and directs it along the perimeter of the yurt, then away. There is no opportunity for the water to pool under the yurt and contribute to the humidity issue.
Although it is early in the experiment, it seems to be working. We have experienced no condensation issues in the first three days. Yesterday, the spring rains hit again, but there is no water under the yurt, and our humidity inside the yurt is no higher than the outside.
As we move through each of the initial seasons in our yurt, we have discovered new challenges and issues that would be uncommon in conventional housing. However, in spite of the spate of concerns, both of us are thrilled with this innovative living accommodation and its two overwhelming benefits: a miniscule cost (with no mortgage to pay) and its roomy in-touch-with-nature atmosphere.

Yurt Flooring

In keeping with the minimal philosophy of living in a yurt, the ideal design will employ a minimum of materials, be as “green” as possible and will be both sustainable and durable.
In our yurt, we have chosen a very inexpensive, basic design and material for our flooring. There are several reasons for this.
Firstly, cost is a factor in the decision as to the type of flooring to use. We opted for materials with a cost of less than $0.45 per square foot, plus $0.10 per square foot for finishes.
Secondly, we wanted to ensure that the frequent traffic directly from outdoors to indoors did not track in excess dirt. Carpeting would have trapped that dirt.
Thirdly, the location of the yurt in a wooded area would have attracted insects such as ants. By constructing flooring with a hard surface, we eliminated nesting sites for those insects.
Fourthly, we wanted a floor that would remain cool in the summer and able to adapt to winter conditions. With the hard surface, we were able to lay down area carpets that we already owned in strategic locations, while keeping bare floor at entrances and frequently used work areas, such as the kitchen areas and washroom.
Lastly, we wanted to minimize weight of the flooring, since we built the yurt on pads and posts, rasther than embedding pillars into the ground.
To accomplish all four goals, we used ¾ inch oriented strand board as sub floor material, with 1/8 inch good one side plywood laid at a ninety degree angles to the subfloor as the main floor. The plywood was screwed to the underlay using three quarter inch wood screws with threads the full length of the screw. The use of full-length threads is essential, so that the screws can be countersunk into the thin plywood.
Lastly, we used a clear varnish to coat the surface of the flooring, making sure to pay special attention to the high traffic areas.
Since installing this flooring, we have found that it works remarkably well, and shows a sheen and grain similar to good-quality hardwood or laminate flooring, at one quarter of the cost.
However, some problems have arisen. On occasion, we stored 20 pound propane tanks on the floor, and, with changing temperatures, the tanks attracted condensation. This condensation accumulated in a ring on the floor. To remove it, we lightly scoured the area with a Javex and water mix, with modest success. The only other problem has been a slight separation, due to the thinness of the material, in spots where insufficient screws were used.
This flooring has answered all five of our criteria for the design, and is recommended for anyone contemplating an inexpensive flooring alternative, whether in a yurt or cabin.

Yurt Trusses Withstand Heavy Snow

One of the concerns that we had when we constructed our yurt was that the winter snow load might be too stressful for the design if the roof. In our part of the continent, we get a fair amount of snow and lake effect snow (120 cm per winter, or 47.5 inches). While this is less than the mountainous areas or the eastern seaboard often gets, our snow stays from November until late April.
The roof trusses are designed with two-by-fours installed 24 inches on centre at the wall top plate, merging to 1.5 inches at the apex of the yurt dome. Most of the conventional, commercial yurts have a similar truss distribution, and claim that they are sufficiently solid to withstand normal snow loads. However, those manufacturers also offer wind and heavy snow load reinforcement options. Our design has an additional drawback: it is designed with a 28 degree slope, instead of the 40-45 degree slope that is needed to ensure that snow slides off the roof.
In order to distribute the weight of the snow, we installed collar ties at the seven-foot point on each truss (our yurt has a 28-foot diameter), with hurricane ties at the wall plates. To ensure lateral and diagonal stability, we used a 3/8 inch aircraft cable, adjustable through use of a turnbuckle, looped through the ends of each truss. Three by six inch reinforcing plates are affixed within two inches of the top and bottom of each joined wall section.
During the fierce winds that we encountered in late October, there was absolutely no movement of the yurt, providing us with some sense of security that the structure was sound. However, lateral wind is not comparable to vertical pressure of weight, so we have had to wait until the snow arrived to test our design.
As of January 26, we have received 10 centimetres more than the entire seasonal average of snow for our area, so measuring the impact of the snow load for a typical season is possible.
Not only has the roof assembly withstood the entire load, but it has not sagged more than 1 centimetre (1/2 inch), yet the snow depth is almost 8 inches on the lower third of the roof. To further test the strength and stability of the trusses, I climbed on the roof and put my entire weight on the mid-point between collar tie and wall plates, and collar tie and dome. No sag was noticed.
Given the additional reinforcing measures that we incorporated into the design, this durability is to be expected. However, it is welcome to see that theory and practice meet, when it comes to the strength of our design. Consequently, I have no hesitation in recommending a similar layout if you are contemplating construction of your own yurt.