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.