Passive Ger : Energy & Moisture Performance

Energy and Moisture Assessment

The driving force behind the Passive Ger is the challenge of adapting a Mongolian ger to meet that the Passive House criteria to reduce the ger’s heat loss, energy consumption, and moisture damage. Because the Passive House Standard is one of the highest construction standards for energy efficient buildings (and can often be fairly expensive) - the goal is to use the standard as a guideline in order for the building performance of Ger to leapfrog into a significantly more energy efficient assembly - ultimately adapting the Ger through a simple application of 21st century building technology. 

To meet the Passive House Standard, the total energy consumption should not exceed 120 kWh/M2/year. A large portion of this energy is dedicated to heating water for household appliances and domestic use. The energy efficient construction standard is particularly appealing for Ulaanbaatar’s climate because the strategic application of building materials enables the home conserve energy - reducing the heating and cooling load on the space ( typically requiring an annual demand to be less than 15kWh/M2/year). Using this design strategy, therefore could significantly improve the performance of the ger by: adapting the Ger’s assembly to be highly insulated, have no thermal conduction of the building materials between the interior and exterior of the home, and reduce the amount of air filtration that escapes the building envelope through poorly designed and installed construction details. 

The building science assessments of the Passive Ger were conducted by three parties.

1. Building Technology’s Engineering Company (BTEC): is a Mongolian building science engineering firm. BTEC used a German modeling tool to assess the total energy loads on the building, however their assessment did not include the vapor and air barrier specified in the drawings as the organization believed these materials to not be important when calculating the heat loss and energy load on the building. 

2. Saint-Gobain: CertainTeed: is a North American manufacturer of building materials for both commercial and residential construction. The Energy and Moisture Group within the CertainTeed Platforms based in Northboro Massachusetts. The group evaluated the heating degree days, energy needs, solar gain, surface and heat losses of the design, and finally simulated moisture condensation within the wall/roof assembly for the Passive ger prototype.

3. Nomadic Synergetic Partners: The third and final energy and moisture assessment was conducted by NSP Architects, based on the final construction documents their firm developed.

Climate Assessment

Buildtech’s climate research indicates that the average temperature range in Ulaanbaatar has a typical annual range of -25°C – 18°C.

The three graphs in Figure 2 on the left demonstrate a three part assessment of the Passive Ger Design throughout the year. The first graph determines the external air temperature throughout the year in Ulaanbaatar.  The second graph outlines the overall heating load for the Passive Ger throughout the year; measuring how much heat is needed to reach comfort temperatures of 19°C - which is a good general approximation of climate. The third graph summarizes all other energy and environmental loads on the Passive Ger including the amount or air filtration, the solar, lighting, persons, and devices energy loads on the housing system.

What makes Ulaanbaatar’s climate especially challenging to design for are the most extreme winter days where the temperatures can drop as low as -40°C . The heating system has to be accurately dimensioned for the heating load of the coldest day of the year, even though outside the average annual demand. For example on February 15, the coldest day of the year, BTEC estimates this heating load would approximately be 2,701kWh, thus demonstrating the required heating load dimension of the final selected heating system.

Heating Distribution Summary

To calculate the energy efficiency of a building, the total energy load must be accounted for. BTEC generated a comprehensive study of the total energy gains and losses of the Passive Ger. Their simulations accounted for a total energy consumption of 8167.3 kWh (221.7 kWh/M2/year). When calculating the average yearly heating energy consumption per M2, from the total of 6133.1kWh, the final result was 166.66 kWh/M2/year. (See figure 3)

The Heat Inflow Chart, demonstrates the total amount of added heating loads to the building, including the; heating, passive solar gains, persons, electronic devices, lighting, and ventilation loads. The total Heat Inflow according to BTEC’s calculations amounts to approximately 9,847.9 kWh. 

A Heat Outflow Chart was also developed to demonstrates the amount of heat loss throughout the year through the ventilation systems and general passive transmissions. The calculations do not account for a cooling system as to reduce the Passive Ger’s material, building, and operational costs. The total Heat Outflow’s calculation is therefore 9,849.1 kWh. 

Lastly, as the Passive Ger’s assembly is an open floor plan a majority of the heat distribution generally evenly dispersed within the living room, kitchen, bedroom, and loft area. However as the bathroom area is separate from the central heating system, a small additional heater may be required to achieve thermal comfort.

Heating and Energy Load Assessment

Due to the project’s overarching goal to create an energy efficient ger that is to be permanently adapted for the ger areas, Saint-Gobain’s calculations primarily focused on included; the heating degree days, energy needs, solar gain, surface and heat losses of the design, and to conclude moisture simulations for the Passive Ger Design. *

Average Heating Degree Days

Heating degree day (HDD) is a measurement designed to quantify the demand for energy needed to heat a building, deriving measurements from the outside air temperature of the local site . In this case, CertainTeed’s Energy and Moisture group has calculated the total number of heating degree days in Ulaanbaatar from 1998 to 2016. The heating degree days for each year are the total number of days that have an average temperature that is below 18.3 °C. In order to maintain an internal thermal comfort, the Passive Ger therefore has to be heated - which is calculated in conjunction with the R-values of the Passive Ger’s building envelope (See table below for CertainTeed’s total R-Values accounted per each component of the Passive Ger Assembly).  

Based in the Energy and Moisture’s team’s results the team has calculated an Average Net Energy Required (represented in the graph as a blue dotted line) of 7823 kWh/yr and an average 95% Net Max Energy Required (represented in the graph as a orange dotted line) of 8707 kWh/yr - in the worst case scenario. 

If the total area of the Passive Ger is 48.92 M2, than the Average Net Energy Required is approximately 159.9 kWh/M2/year (not including energy gained through Passive Solar heating gains).  Based off the 95% confidence band of the Net Max Energy Required, the Passive Ger will consume 177.9 kWh/M2/year (not including energy gained through Passive Solar heating gains). As a result, even in the worst case scenario - the Passive Ger is meeting the energy requirements of the Mongolian Green Finance Corporation. 

Furthermore, because of the energy efficient changes in the Passive Ger design, families would reduce their energy consumption - no longer burning an averaging of 939 kg to 1,045 kg of coal each year - assuming that the energy density of coal is 8.33 kWh/kg. In comparison to a traditional 5 khana ger, families would be burning an average of 3 and ½ less tons of coal.

Solar Heat Gain

Due to the Passive Ger’s South facing triple glazed window a significant amount of passive solar gain is produced.  Of the number of 4,380 hours of possible sunshine in Ulaanbaatar; there is an average 2,791.5 hours of sunshine per year. And if the area of the window is 2.6 M2, including the amount of diffusion of energy that is radiated and transmitted through the South Facing window is 1,465 kWh. (See figure 6)

Moisture Assessment: Saint-Gobain

While thermal insulation is critical in order to enable the Ger’s building envelope to conserve heat, proper moisture management is essential in order to refrain from condensation and eventually mold growth causing serious long term damage inside the building envelope. 

In a traditional Mongolian Ger, families have to take down their Ger a minimum of twice a year - once in the fall and another in the spring - to prevent the felt from mold growth by exposing it to UV rays and airing out the felt below the cotton exterior fabric. However, as families are moving to the Ger Areas of Ulaanbaatar and looking to install themselves permanently around the City, they are no longer interested in conserving the mobile qualities of the Traditional Mongolian Ger - especially as the mobile properties of the Ger were only essential for nomadic herders - moving throughout the seasons for their herd to find fuller pastures. 

As a result, in the Passive Ger enclosure is developed to have a permanent and proper application of both an air barrier and a vapor barrier. Based on Saint-Gobain: CertainTeed’s recommendations, moving from inside to out, the placement of the building materials are defined within the following order; the vapor barrier is between and inner set of Khana and Uni and the insulation, followed by the air barrier and an outer Khana and Uni on top - which simultaneously holds in the 4 layers of insulation and air barrier down through compressive strength, as well as creating a 3 centimeter gap between the air barrier and exterior PVC membrane to allow for proper airflow and reduce the risk of condensation. Base on the condensation analysis in Figure 8, the WUFI model demonstrates that this assembly has a relative humidity that is less than 90% - a passing criteria. Traditional passing criteria requirers humidity levels that are less than 95% anywhere in the assembly. 95% humidity levels could present itself as condensed liquid water, ultimately creating a moisture peak that is greater than 20% which would stimulate mold growth over time.

Energy Efficiency Gains

A traditional ger is a housing system that has an exorbitant amount of heat loss. Building Technology’s Engineering Company conducted a study in 2012 to calculation a traditional 5 Khana Ger’s annual heat loss. In their calculations they accounted for 2 layers of felt on the wall and roof, a floor, skylight, and door in the assembly. According to BTEC calculations, a traditional ger losses approximately 13,028 Q, BT (see figure 9).   

In comparison, the Passive Ger is assembled to be highly insulated, airtight, and vapor resistant - reducing thermal conduction and air filtration between the inside and outside temperatures of the Passive Ger. As a result, the final heating load calculations of the Passive Ger are between 159.9 - 177.9 kWh/M2/year - which is approximately 8 times more energy efficient than a traditional ger.

Although the Passive Ger will not meet the final metrics for the assembly to be a certified Passive House, the significant reduction in energy consumption is a huge improvement in comparison to a traditional Ger.

Clean Energy Source

One of the most important advantages of developing an energy efficient Ger is its ability to reduce the running cost of an alternative electric heating system, such that the price of the alternative heating system could be as cost efficient as a coal burning stove. This is a major challenge as coal is the most cost effective heating source for families in the Ger Areas today; where approximately 1 months worth of coal consumption in the winter (1.3 tons of coal) is approximately 160,000 MNT(1). 

Currently, families who have electrical heating mats in their traditional Gers spend an average total of 130,000 MNT per month on their electrical bill in comparison to families who only use their electrical supply for household appliances - which is on average approximately 20,000 MNT per month. If an electrical heating system is used, it is often used in addition to the coal burning stove, making this approach to heating a traditional ger costly and often unsustainable for most middle income families. As a result, coupling a clean energy efficient source with an energy efficient building envelope is the optimum approach to significantly bring down the cost of the alternative heating system while reducing air pollution. 

For the Passive Ger, a Chinese made air-to-air heat pump system has been selected based on a recent study that was conducted by Kirk Smith. The model has an “enhanced capacity in cold ambient conditions, COP is up to 2.0+ at the outdoor temperature of -20C, it can run normally at the outdoor temperature of -35C, includes automatic defrost, and has a working fluid of R-32”. More importantly, the running cost of the air-to-air heat pump in a traditional 5 Khana Ger was a total of 257 USD in comparison to 335 USD for the total heating season from 2017-2018 for a same sized, same square footage household.

Click here for more information on the air to air heat pump.

Modern Plumbing System

Soil and water contamination from the pit latrine system in the Ger Areas of Ulaanbaatar is also a major pollution challenge Ulaanbaatar faces. As these peri-urban communities are approximately one-fourth of country’s population, the “inadequate disposal of human fecal waste, sanitation-related diseases “ create increasing risks for soil and water contamination”(2). This considerable human health challenge requires for an sustainable housing proposal for the Ger Areas to include an engineered plumbing system that provides an “on-site (de-centralized) fecal waste management system” that is sustainable without adequate urban infrastructure and can compost waste and water treatment independently from local government support.

The Passive Ger therefore uses a 3 part septic tank system with Brocadia anammoxidans, or anammox bacteria, which effectively eat human waste(3). The system filtrates 90 percent of the solid waste for approximately 1.5 million MNT, making the sanitation system more affordable in comparison to traditional sanitation products that can cost as much as 7 million MNT. The application of this plumbing system could have a significant social and environmental impact in reducing the soil and water contamination of the Ger Areas, while also allowing families to begin improving the state of their hasha (there plot of land) through modern plumbing and water management systems,

Estimate of CO2 Emission

In no longer using a coal burning stove, the CO2 emission produced by the Passive Ger’s building’s operation is close to zero. The alternative heating solution is powered by electricity that stems from one of Ulaanbaatar’s local coal burning power plants, there coal is burned to generate mechanical power which is then converted into electricity energy. (4)

Conclusion

In conclusion the final heating load calculations of the Passive Ger is between 159.9 - 177.9 kWh/M2/year according to Buildtech’s and CertainTeed’s calculations. These results vary slightly due to each party’s modeling methods. Ultimately , however, the results meet the heating load requirements of the Mongolian Green Finance Corporation. And furthermore, in comparison to a traditional Mongolian Ger, the Passive Ger is now significantly more energy efficient and moisture resistant.

In the future more extensive modeling and testing should be conducted on the physical prototype in order to ensure the airtightness of the assembly, in addition to conducting more accurate assessments using passive house design tools such as PHPP and other dynamic energy, thermal bridge analysis tools.