Best House Wrap to Prevent Condensation Issues in Yurts
Because the cotton-based outer canvas of a yurt is water resistant and not waterproof, we add a layer of house wrap between the felt insulation and the canvas – this will help prevent condensation issues in yurts.
The house wrap acts as an additional barrier to block any humidity that manages to get past the canvas, while still allowing the yurt to breathe. This dynamic created by the outer layers is what makes the yurt so efficient, comfortable, and healthy (in a way). However, it should be noted that the house wrap is a compromise and does reduce the breathability.
This solution can reach its limit in the freezing temperatures of winter, when the humid air inside the yurt runs through the felt, hits the cold layer of wrap and freezes, disabling the wrap’s breathability.
If too much condensation accumulates in the felt, it may drip down the yurt or leave humidity stains in the inner liner.
The same process can occur in above freezing temperatures when humidity builds within the yurt and is quickly followed by rainfall. This causes the yurt’s roof to cool much faster than the air does. In this situation, yurt dwellers are often confused and think that rainwater is coming through the roof.
The best strategy to continuously monitor humidity production and ventilate when cooking or producing extra vapour (ex. using propane).
Heating with a wood stove to dry the yurt inside (keeping an opening in the toono) is another options when the yurt was left unattended for a while or if water had found its way in.
A Better Wrap for Yurts to Prevent Condensation Build-Up
But what if there was a better wrap?
Over the years, we’ve tried a few different brands.
In the beginning, we were using Novawrap Aspire, however, due to the fragility of the product, quick diminution of quality, and poor response from the company, we made the easy decision to turn back to Mento 1000.
We recently began evaluating other wraps and just did a comparative test on a 3-wall (14’ diameter) yurt. To do this, we made a roof wrap out of 4 different brands and installed it on a double layer of felts. Over the next few days, we boiled over 100 litres (over 25 gallons) of water inside the yurt alongside outdoor temperatures of -24C (-11F). We let the yurt cool down occasionally, but always kept it closed and tight.
The simple experiment showed interesting results.
On the bright side, one of the wraps was clearly superior and trapped significantly less frost under its surface. It remained relatively dry. Most of the vapour had escaped, following the path of least resistance, as the felts were mildly moist and showed few water stains in the ceiling. It seemed to prove the necessity for ventilation (vapor will follow the path of least resistance) and allowed us to identify a better option to use as a roof underlayer from now on.
What’s to Come for Yurt Humidity Control in the Future?
We wish to keep the Mongolian ger’s original characteristics, as we have so much respect for this timeless dwelling and want it to remain as simple as possible. However, now that they are used in other climates and have purposes aside from nomadic life, we must understand how the dwellings react to new variables and relay this information to our customers.
The best first precaution: Monitor humidity and ventilate. Humidity stains can be removed by spraying a solution of bleach or vinegar.
The article mainly applies to Authentic Mongolian yurts. Modern yurts experience similar condensation issues, however the process is quite different.