Research on Envionmental Resistance Performance of Disaster TemporaryHousing Modular Houses using Large-Scale Environmental Testing Chamber

1.1. Research Background and Purpose

Escalating climate change increases natural disaster damage in South Korea. The Korean government has utilized tents or mats in large indoor spaces, such as village halls, gyms, and school playgrounds, or provided prefabricated, apartment, and container houses for disaster victims. Gyms or school playgrounds can rapidly accommodate many people in response to sudden disasters; however, they often cause inconvenience owing to the outdoor locations or absence of personal living space, sanitation, heating, and cooking facilities. Open spaces also cause such problems as invasion of privacy and exposure to noise [1].

Temporary houses (prefabricated and container houses) involve the inconvenience of moving to residential spaces several times owing to their prolonged setup times, and their low performance (e.g., insulation, heating, and the impacts of external weather conditions) causes other problems [2].

For modular houses, main structures, electric/water equipment, and finishing materials that are produced in advance in factories are assembled at the site. Since 70%–80% of major members and components that constitute housing can be produced in standardized module units, pleasant temporary living spaces can be prepared at a low cost within a short period of time. This study aims to analyze the applicability of modular houses as temporary residential facilities by measuring their insulation and waterproof performance to address problems with conventional temporary residential facilities.

1.2. Research Scope and Methods

The research scope was limited to modular houses constructed and used for residential purposes to examine their applicability as temporary residential facilities. The research methods of this study are as follows.

First, the direction of research is set by analyzing previous studies related to conventional temporary residential facilities.

Second, based on the analysis of previous studies, heat and waterproof experiments are performed, and the results are analyzed.

Third, conclusions and future directions on the applicability of modular houses as disaster temporary housing are presented based on the analysis results.

2.1. Status of Temporary Residential Facilities

K. H. Kim et al. conducted a satisfaction survey with the victims of the Pohang Earthquake who stayed in indoor gyms. They raised complaints about the unsanitary conditions caused by the outdoor locations of convenience facilities (e.g., bathrooms, kitchens, and laundry) and the difficulty in protecting privacy owing to the lack of sleeping and personal spaces [1].

S. H. Lee et al. investigated resident satisfaction by conducting a field investigation and a survey of disaster victims who were supported with temporary housing. They found that most disaster victims had evacuation experiences for approximately four months (or more), during which temporary housing was provided after the occurrence of the disaster; moreover, when temporary housing is provided, the first requirement is to improve indoor ventilation, the number of rooms, and the support period. The survey results show that the living area, insulation performance, and safety under external weather conditions (e.g., rain and strong winds) must be improved [2].

Y. R. Seo et al. also conducted a survey with disaster victims on satisfaction with conventional temporary residential facilities. They presented the status of conventional temporary residential facilities based on the survey results, including insufficient sanitation facilities, low comfort caused by high indoor humidity and noise, and inconvenience caused by privacy exposure [3].

This study aims to analyze the applicability of modular houses to address the problems with conventional temporary residential facilities derived from the results of previous studies. Experiments were performed to measure thermal and waterproof performance, which is closely related to residential comfort.

3.1. Target Modular House

In this study, a residential modular house that meets the thermal transmittance standards and equipment for buildings by region specified in the Temporary Housing Prefabricated Housing Operation Guidelines [4] was selected as a target (Fig. 1. and Table 1.). It is a unit-type modular house, and the main materials of the outer wall are steel frames, mineral wool, and synthetic resin finishing materials.

Fig. 1.

Modular house

Table 1.

Detailed specifications of modular homes

3.2. Experimental Facility

The large-scale environmental testing chamber used is a large-scale experimental facility in which various environmental conditions can be set, including temperature, rain, snow, and sunlight. To measure the modular house’s environmental resistance performance, experiments were performed by simulating temperature, rain, and strong wind environmental conditions (Fig. 2. and Table 2.).

Fig. 2.

Large-scale environmental testing chamber

Table 2.

Large-scale environmental testing chamber detailed specifications

3.3. Thermal Performance Experiment

In the survey on satisfaction with temporary housing, the problem of poor insulation performance was raised [3]. Accordingly, the thermal performance (insulation and condensation) of the modular house was measured to analyze whether the problem could be improved.

To measure the insulation performance of the modular house, the Building heat Loss Coefficient (BLC) was calculated after setting high-temperature and low-temperature environmental conditions. The environmental conditions of the testing chamber were set to 50℃ for summer considering the maximum temperature and the roof surface temperature caused by sunlight in Korea and –20℃ for winter considering the minimum temperature, roof surface freezing, and snow. Indoor environmental conditions were set based on the seasonal comfort range of ASHRAE Standard 55-2017 [5] (Table 3.).

Table 3.

Environmental conditions of insulation performance experiment

The experimental procedure for high-temperature environmental conditions is shown in Fig. 3. and that for low-temperature environmental conditions in Fig. 4.

Fig. 3.

High temperature environmental conditions profile

Fig. 4.

Low temperature environmental conditions profile

• [Step-①] Place the target modular house in the testing chamber and set the environmental condition of the chamber to 50℃.
• [Step-②] Set the indoor environmental condition to 24℃ and check whether chamber and indoor environmental conditions remain constant.
• [Step-③] Measure the data required to obtain BLC.
• [Step-④] Calculate BLC after setting chamber and indoor environmental conditions to standard atmospheric conditions.

• [Step-①] Place the target modular house in the testing chamber and set the environmental condition of the chamber to -20℃.
• [Step-②] After reaching -20℃, check whether the set environmental condition remains constant.
• [Step-③] Maintain the indoor environmental condition at 22℃ by operating indoor air conditioning.
• [Step-④] Measure data and calculate BLC when chamber and indoor environmental conditions remain constant.

To analyze the modular house’s thermal performance, the theoretical BLC value that used the thermal transmittance of each part (BLC_KAT) was compared with the values calculated by measuring the electrical energy of cooling/heating devices and the air-conditioning flow rate (BLC_COP, BLC_mcdt).

First, BLC for each part (BLC_n) of the building (ceiling, floor, walls, windows, and doors) was calculated by multiplying its area (A) and thermal transmittance (U) (Eq. 1)

The theoretical BLC value (BLC_KAT) was obtained by adding the calculated BLC value of each part (BLC_n) (Eq. 2).

(BLC_1~5 : In order of ceiling, floor, walls, windows, and doors)

The cooling/heating load (Q) was calculated by multiplying the electrical energy (W) of cooling/heating devices measured at [step-③] by COP (Eq. 3), and the BLC measurement (BLC_COP) was calculated by dividing it by the indoor and outdoor temperature difference (ΔT) (Eq. 4).

The mass flow rate ($$ \dot{m}$$) was calculated using the discharge temperature, intake temperature, and wind speed of cooling/heating devices measured at [step-③]. The total heat loss/heat acquisition (Q) was calculated using the mass flow rate, specific heat of the air (C_p), and difference between the discharge and intake temperatures (ΔT_i-o), and the BLC measurement in consideration of the air-conditioning flow rate (BLC_mcdt) was calculated by dividing it by the indoor and outdoor temperature difference (Eq. 7 and Eq. 8).

Equipment was arranged to measure the modular house’s condensation performance, as shown in Fig. 5. Chamber and indoor environmental conditions were set based on KS F 2295 [6] and design standards for condensation prevention in multi-family housing [7] (Table 4).

Fig. 5.

Deployment of condensation performance experimental equipment

Table 4.

Condensation performance experiment environmental conditions

The experiment was conducted in stages, as shown in Fig. 6.

Fig. 6.

Condensation performance experimental profile

• [Step-①] Set the chamber environmental condition to a temperature of -20℃ and indoor environmental conditions to a temperature of 20℃ and a relative humidity of 40%.
• [Step-②] Check whether chamber and indoor environmental conditions remain constant when the chamber temperature reaches –20℃ (stabilization).
• [Step-③] Increase the indoor relative humidity from 40% to 50%.
• [Step-④] Maintain the environmental conditions for a certain period of time when the indoor relative humidity reaches 50%.
• [Step-⑤] Visually inspect the occurrence of indoor surface condensation.
• [Step-⑥] Calculate results after adjusting chamber and indoor environmental conditions to standard atmospheric conditions.

The dew point temperature (T_dc) was calculated through the measured indoor temperature (T) and humidity (RH) (Eq. 9). When the measured surface temperature of each indoor part (ceiling, floor, walls, windows, and doors) was high, no condensation occurred.

b, c : a constant(b = 17.62, c = 243.12)

3.4. Waterproof Performance Experiment

To measure the waterproof performance of the modular house, the house and equipment were arranged as shown in Fig. 7.

Fig. 7.

Layout of waterproof performance test equipment

For storm environment simulation conditions, the maximum precipitation per hour and maximum wind speed in the summer over the last 10 years were investigated. Precipitation was found to range from 90 to 110mm/h, and wind speed ranged from 17 to 30m/s. Environmental conditions were set considering weather information and the performance of equipment (Table 5.).

Table 5.

Waterproof performance test environmental conditions

Fig. 8.

Waterproof performance experimental procedure(Front, right, left, back in that order)

4.1. Thermal Performance Evaluation

To analyze the modular house’s thermal performance, the theoretical BLC value (BLC_KAT) and measurements (BLC_COP, BLC_mcdt) calculated using each equation were compared and analyzed (Table 6.).

Table 6.

Experimental results of insulation performance

The results in Table 6. show that the theoretical value (BLC_KAT) was approximately 56% lower than the measurements (BLC_mcdt, BLC_COP), and the measurements (BLC_mcdt and BLC_COP) were similar with a relative error of 23%.

Substantial differences existed between the theoretical value and measurements because the theoretical value (BLC_KAT) represents ideal performance as it is the value calculated by considering only the thermal transmittance of each part of the modular house, while the measurements (BLC_mcdt, BLC_COP) include the heat loss caused by infiltration through envelop angle, joint, window, and door gaps. Since considerable differences were observed between the theoretical value and measurements, preparing methods and standards for evaluating the performance of temporary housing modular houses through experiments with various samples of modular houses will be necessary in the future.

4.2. Condensation Performance Evaluation

When indoor walls and windows were visually inspected, no condensation was found, as shown in Fig. 9. A comparison between the calculated dew point temperature and each surface temperature (Fig. 10.) revealed that all surface temperatures were higher than the dew point temperature, which indicates that no condensation occurred indoors, and wintertime insulation performance was secured.

Fig. 9.

Checking for condesation in a modular house(Order of windows, doors, and walls)

Fig. 10.

Comparison graph of dew point temperature and each surface temperature

4.3. Waterproof Performance Evaluation

Indoor leakage was visually inspected after stopping environmental conditions at [step-③]. The parts inspected were the angles and corners of each wall as well as window and door gaps, which are considered vulnerable to leakage.

No leakage was found in the parts as shown in Fig. 11.–13. If the modular house is used as a temporary residential facility, no leakage problem will arise even in strong wind and rainfall environments during summertime.

Fig. 11.

Checking for window waterproofing performance

Fig. 12.

Checking for corner and angle waterproofing performance

Fig. 13.

Checking for door waterproofing performance