Facade System Design for Insulation and Prevention of Condensation in Apartment Housing with Expanded Balcony

Transcription

1 Facade System Design for Insulation and Prevention of Condensation in Apartment Housing with Expanded Balcony Seonyong Yoo 1,a, Sang-jin Kim 1,b, Chungkeun Lee 2,c, SukWon Jee 2,d, Doosam Song 3e, Taeyeon Kim 4,f, Seung-Bok Leigh 4,g 1 Graduate Student, Department of Architecture, Yonsei University, Korea, Doosan Bldg., -7, Nonhyun-Dong, Kangnam-Gu, Seoul, , Korea 3 Professor, Sungkyunkwan Univ., 3 Chunchun-dong, Suwon, Korea, Professor, Department of Architecture, Yonsei University, Korea, a seonyong@yonsei.ac.kr, b 9981@yonsei.ac.kr, c yckeun@doosan.com, d jswon@doosan.com e dssong@skku.edu, f tkim@yonsei.ac.kr, g sbleigh@yonsei.ac.kr ABSTRACT According to the legalization of balcony expansions in apartment since January 6, most of the apartment houses now are built with expanded balcony space. The existing balcony space was physically a buffer space of between the outside environment and the inside environment. In addition, it was a space that functioned to minimize the indoor environmental changes in relation to external weather changes. However, as apartment houses with extended balconies have become more common recently, the possibility of dew condensation increased due to the weakening of the insulation capacity as the space that can carry out these environmental buffer roles have disappeared. Also, the indoor thermal environment has been weakened. Thus, this paper seeks to resolve problems related to the expansion of balconies by recognizing these problems and presenting a new method that improves the insulation and condensation capacity in the façade system designs that an apartment house with an extended balcony should have. KEYWORDS: Extended balcony, Insulation, Condensation, Ventilation 1. INTRODUCTION As the number of requests to widen the balcony space given in apartment houses for service spaces and use it as a living space has increased recently, the Ministry of Construction and Transportation have legalized the expansion of balconies in apartment houses in January 6. Most of the apartment houses built in 7 are constructed with extended balcony space according to the demands of the consumers who want larger indoor space. In terms of environment control, the balcony is a connecting space that physically links the outdoor environment and the indoor environment. In addition, the balcony functions as a buffer space that minimizes the indoor environmental changes in relation to the external weather changes. Therefore, the expansion of the balcony space can cause problems such as the weakening of the insulation capacity, condensation, the diminishing of perceived thermal comfort, and increase of energy costs due to the weakened control of the indoor environment for dealing with the outdoor environment. Numerous researches on the expandedsion of balconies and condensation have been carried out in the past. However, most of the researchesthem were restricted within researches limited on the capacity of the actual window fittings such as researches devoted only to expansion, investigation of the actual conditions in the generation of condensation, investigation of the temperature and the humidity of 183

2 indoors and outdoors and surface temperature of the region in which condensation was produced through experiments, the evaluation of the condensation preventing mechanism materials through experiments, an estimation of whether condensation will generate or not, and presenting the optimum thickness of insulation rather than indicating an overall solution. Therefore, constructing a rational façade system design method that reflects the actual living conditions andor environmental condition is urgently needed to prevent condensation in households. Moreover, things that were not much of a problem in existing apartment houses with balconies have been raised as issues that must be solved. This research recognizes these problems and attempts to solve the insulation and condensation issues caused by extending balconies by presenting a new method in the façade system design that an apartment house with expanded balcony must have. For this, an investigation on the actual condition where condensation is generated waswill be carried out through a field study and a comparison of the capacity of the extant method and the improved method is to bewas carried out through a mock-up test. 2. PROPOSAL OF A NATURAL VENTILATION DOUBLE-SKIN FAÇADE TO PREVENT CONDENSATION 2.1 The concept of condensation and its cause Condensation refers to the phenomenon in which water drops are formed when air that includes vapour comes in contact with a cold surface that has a temperature lower than the dew point of that air. Condensation is ultimately produced by air of a relatively high humidity and a cold surface temperature when various factors such as the temperature difference of indoors and outdoors, excess production of humidity indoors, thermal characteristics of or defects in constructing building materials, lack of ventilation due to living styles, and moving in before the apartment has become completely dry right after construction all act together. Physically, the problem can be solved easily when the balance between humidity and temperature is adjusted since it is influenced by humidity indoors and temperature. Thus, this research proposes a natural ventilation double-skin façade that has an insulation capacity of the outer face along with a ventilation function to discharge vapour. 2.2 The concept of the natural ventilation double-skin façade The characteristics of the double-skin façade used in this research are as follows. The façade protects the inside from the influence of the outside weather and forms a wider midaircavity layerspace than the extant double-fittingswindow. Furthermore, not only is natural ventilation possible as an opening is installed at the top and bottom on the outside and at the top inside, but it also reduces thermal heating loads by importing air from the midair cavity spacelayer that has been ascended by solar radiation. Moreover, it is designed to decrease the production of condensation on window surfaces by discharging the vapour produced indoors from cooking and the laundry to outside. In addition, the rate of the overall heat transmission was reduced by strengthening the insulation capacity of the overall façade by using a Low-e glass in the inner fittingswindow. Furthermore, it is advantageous in soundproofing and was designed to cope actively against outside weather. Although it is not prevalent in South Korea yet, it was designed so the midair cavity space is divided to allow the installation of blinds within the layer the midair layer for the blinds to use the absorbed solar radiation energy to increase the ventilating power of the midaircavity layer and discharge thermal energyheat smoothly. 3. APPLICATION EXPERIMENT OF THE NATURAL VENTILATION DOUBLE-SKIN FAÇADE SYSTEM 3.1 Abstract of the case study building The subject for the application, evaluation, and comparison experiment of the natural ventilation double-skin façade system is the apartment built in Gyeonggi-do Namyangju-si by D construction company (16~22 levels, 7 buildings, 32 pyeong single area type). Presently, 1.8% of the construction 184

3 has been completed while the moving in date is expected to be sometime in February 8. The case study households units are house number 2 and 2 inside 7-dong. They are in the same building and are vertically connected householdunits. Except for the fact that they are on different floors, the house umber units are same condition inin terms of their location and direction. The indoor temperature and humidity according to each outer facefacade system applied was measured and whether or not condensation is produced, as well as insulation capacity, changes in the indoor thermal environment, and ventilation capacity according to the changes in the operation mode of the vent slot were measured in the expansion comparison household house umber houses number 2 and 2. For the case study householdunit plane and indoor finishing conditions, house number 2 on the first floor is a model house that was built ahead of the overall building schedule as the construction in expanding the living room, bedroom #2, bedroom #3, and the kitchen, and the indoor finishing construction are already complete, and basic furniture are set up. House number 2 on the second floor is in a state where the construction to expand have not been completed as it is a unithousehold that is following the construction schedule of the apartmenthouse umber complex. To maintain the testing conditions most identically to the comparing household unit 2, the inner window between the balcony space and the living room was removed, a heat insulator was installed in the balcony floor and the walls, and a simple construction like installing a light-weight partition in the opening between the living room balcony and the inner room balcony was carried out. Figure 1. Location and floor plan of the experimenting households units within the house umber apartment complex 3.2 Composition status of the outer face for the experiment - The composition of the outer facefacade system that is installed when expanding by the D construction company (installed in house number 2): composed of an inner ㆍ outer window 16mm[glass+air+glass(+6+)], 89mm cavity space, total width 228mm including the midair layer 89mm frame Vent Slot TH 9 range [inside inside] Sloding [inside inside] Sliding Sliding Sliding Casement Casement [outside outside] 228mm [outside outside] 38mm House number 2 House number 2 Figure 2. Location of application and elevation form of window fittings for each unit 18

4 - The composition of the outer facefacade system of the natural ventilation double-skin façade system formed as an alternative(installed in house number 2): composed of an outer window 22mm[glass+air+glass(6++6)], an inner window 22mm[low-e glass+air+glass(6++6)], 24mm cavity space, total width 38 mm including the midair layer 24mm frame 3.3 Contents of the experiment -Investigation period: ~12(comparing ed/experiment:ed house number umber s 2 and 2 for four 3 days) ~1(ventilation mode experiment:ed after changing the mode of house umbernumber 2 for seven6 days) -Space for investigation: living room, window fittingsfittings of living room -Time zone for survey: 2~9: The living room space at night time in winter was the main subject for measurement to examine the present status of condensation production on the outer facefacade and changes in the insulation capacity and the indoor thermal environment according to the application of extant outer facefacade system and the natural ventilation double-skin façade when extending balconies. 3.4 Experimental methods The indoor environment conditions of each household unit during the experimental period set the indoor temperature to 2 by using a domestic gas boilerheater that is generally installed in apartmenthouse umber s. After that, continuous heating was carried out and the indoor humidity was maintained at 4~6% by using the humidifier found in markets to measure the occurrence of condensation on House number 2 House number 2 inner windowdoor fittings, insulation capacity, Figure 3. Measuring location of each fittings and the changes in the thermal environment according to the external conditions during the experiment. To compare and judge the production of condensation on each fittingswindow of the unithousehold with D construction company s outer facefacade system installation (house umbernumber natural ventilation double-skin façade system, each of the temperature and humidity of the inner surface of the inner and outer window and indoor humidity indoors/outdoors fittings was measured and thermocouple and a humidity sensor(sk-sato) were used. A vertical temperature distribution of.1m, 2.m from the balcony window was measured to compare and evaluate the indoor thermal environment changes according to the outer House umber 2 House umber 2 facefacade system installed by the extant D Figure 3. Measuring location of each fittings company and the natural ventilation double-skin façade system. 2) and The measuring heights were the living room floor,.1m (the height of the breathing line when lying on the floor),.6m (the height of the breathing line when lying on the bed), 1.1m (the height of the breathing line when sitting), 1.7 (the height of the breathing line when a person stands) and a globe thermometer and a humidity sensor were installed at 1.1m each. To measure the surface temperature of each of the outer facefacade system, it was installed in in the outer face of house umber 2 and the window frame, fittings frame,glass frame, glass (edge,.6m, 186

5 .1m, center), and the center of the midair layercavity of the fittings of the top and bottom part of the indoor/outdoor window of house umber 2 and measured every five minutes. 4. ANALYSIS AND STUDY OF EXPERIMENTAL RESULTS 4.1 Analysis of comparison experiment results of the applied façade systemouter face of each household 1) Indoor/outdoor temperature changes of each household As presented in Figure 4 and, the outside air shows a temperature change range of -.2 ~6.1 while the average temperature shows a temperature change of.9 throughout the experiment period. The measured results of the indoor temperature show that house umbernumber 2 is 1.2 higher as the average indoor temperature of house umbernumber 2 and 2 are 2.3 and The reason for this is judged that since house umbernumber 2 has a larger overall heating area of radiating heat by 6.2 m2 as heating is impossible in the expanded region of the household in house umbernumber 2 as explained above in the experimental conditions. The average temperature of the surface temperature of the center of the window were. and.7 in each unit, which has a small difference of.2. Yet, the lowest temperature were 17.7 and 18.9 with a difference of 1.2 that is much larger than the average value of.2. When assuming the indoor temperature and humidity are 26 and 6%, the dew point temperature is The surface temperature of the window fittings of in house umbernumber 2 becomes lower than the dew point temperature while it is higher than the dew point temperature in house umbernumber 2, which can produce condensation in house umbernumber 2. Furthermore, it is judged that house umbernumber 2 is advantageous in the elevation of pleasantness indoor comforts as the surface temperature of the glass in house umbernumber 2 is maintained consistently compared to the surface temperature of the glass in house umbernumber 2. Temp( ) Temp( ) : 9: 1 1 1: 1 19: 2 : 9: 1 1 1: 1 19: 2 : - : 9: 1 1 1: 1 19: 2 : 9: 1 1 1: 1 19: 2 : outdoor_t Center_T indoor_t Dew.P_T Cavity_T Figure 4. House umbernumber 2(Temperature) outdoor_t Center_T indoor_t Dew.P_T Cavity_T Figure. House umbernumber 2(Temperature) 2) Comparison of temperature declining rate and possibility of condensation production in house umber s 2 and 2 By using Equation (1) based on the measured data, the possibility of condensation production is estimated during the heating period (December ~ February: 276 hours). The temperature declining rate of window fittings is defined as follows. Here, TDR: temperature declining rate of fittingswindow Tin Tswin TDR = (1) Tin: indoor temperature, Tin Tout Tswin: surface temperature of indoor fittingsinner window Tout: outdoor temperature 187

6 R - R When observing the temperature declining rate graph in Figure 6, it is predicted that condensation will be generated on the glass surface in house umbernumber 2 when the dew point temperature falls to 1.3 and the outside air temperature falls below because the dew point temperature is 1.3 from the designed standard indoor standard temperaturecondition (2, %). Moreover, when the relative indoor humidity increases by 7%, it is predicted that condensation will be produceoccurd on the extant outer facefacade of house umbernumber 2 from outside temperature - 2 with the dew point temperature at 19., while the alternative outer facefacade of house umbernumber 2, condensation will be generated under -1. 2, 9% 2, 8% 2, 7% 2, 6% 2, % 2, 4% Out Temp.( ) Surface Temp.( ) House umber 2 House umber 2 Dew point temperature Figure 6. Comparison graph of temperature declining rates Table 1. Temperature declining rates of each household Classification #House umber 2 #House umber 2 Maximum. value Minimum. value.1.81 Ave.rage value Standard deviation Façade systemouter face capacity to prevent condensation To set the designed standard temperature Envelope ASHRAE U-value PSYCHROMETRIC productionchart NO.1 Ti: Indoor temperaturenormal TEMPERATURE To: Outdoor temperature BAROMETRIC PRESSURE: kpa and humidity for the standard calculation Copyright 1992 Ts: Indoor surface temperature AMERICAN SOCIETY OF HEATING, REFRIGERATING AND AIR-CONDITIONING ENGINEERS, INC. (Using the experiment data) METERS Ri : Convective heat transfer resistance(indoor surface) Dew point temperature of the outer facefacade system capacity, 2 (A building energy economy standard the temperature and humidity of the Dew point temperature heating period in winter (December ~.16.4 U-value 1.2 An estimated surface temperature February: 276 hours) were analyzed. (House umber 2).14 Relative humidity Condensation The average temperature changed from - An estimated surface temperature 17.4 U-value 2. % rising (House umber 2).12 1 The designed indoor 1.6 to 11.2, and the temperature that Minimun standard condition. The designed outdoor U-value 2 6% standard condition 1.6 satisfied 9% was -9.7 while 8% was - 9% -9.7 Maximum.8 U-value The U-value of windows was calculated.4 by using measured data With -9.7 that satisfies outdoor air of Outdoor temperature in winter (12월 ~2월 ) 9% as the design standarded outdoor air standard temperature and at the indoor Figure 7. U-value of the applied outer face condensation designing standard condition 2 and 6%, the façade systemouter face applied by D construction company in house umbernumber 2 had a U-value of 2.W/ m2 and an estimated surface temperature of Furthermore, the outer face applied by a natural ventilation double-skin façade system in house umbernumber 2 had a U-value of 1.2W/ m2 and an estimated surface temperature of.4. For the outer face used as an alternative, the rate of heat transmission of glass was smaller by.8w/ m2 and the surface temperature is estimated to be 3 higher. As shown in Figure 7, at -9.7 of outdoor temperaturethe designed outdoor air condition 9%, temperature range -9.7, and the designed indoor standard condition of 2 and 6%, the minimum U-value to maintain the indoor surface temperature higher than a dew point temperature higher than 16.6 is 2.2W/ m2. When the relative humidity exceeds 7%, the minimum U-value must be smaller than 1.2W/ m2 to maintain the dew point surface temperature above % 8% 7% 6% % 4% 3% % % RELATIVE HUMIDITY DRY BULB TEMPERATURE - C.88 VOLUME - CUBIC METER PER KG DRY AIR 2.9 HUMIDITY RATIO - KILOGRAMS MOISTURE PER KILOGRAM DRY AIR 2 WET BULB TEMPERA 3 188

7 When the relative humidity is larger than 7%, it is judged that discharging vapor by ventilation rather than increasing the U-value is profitable economically and in the aspect of the amount of ventilation of.7 times/h.ach 4.3 Analysis of each operating mode of ventilation During the experimenting period of February 9, 7 ~ February 1, the present status of the indoor and outdoor temperature and humidity of each ventilation mode was observed. The mode operating time was from :~8:, 12 hours at night, and the operating methods of each mode are shown in Figure 8. When the indoor vent-slot was not openclosed as in mode and mode1, the dew point temperature was around. However, in mode3 where the indoor vent-slot was adequately opened, the dew point temperature dropped around as the absolute humidity indoors reduced. In addition, when the vent- slot was closed to an extent where the difference between the absolute humidity of indoors and outdoors was.2, it decreased to half of. in mode. Figure 8. Temperature measuring mode of the alternative facade system The direction of the air flowcurrents can be predicted according to the ccavity temperature when observing the written average temperature data of the testing period of February ~1 ~: in Table 2. As a method to predict air of which direction came inflow direction according to the ccavity temperature and the difference between cavity air and outdoor air andor indoor air temperature, mode has no flow in the air current, mode1 has flows from the outside airdoor to the ccavity direction, mode2 has flows from both sides, and mode3 has flows from the indoorside to ccavity. For mode3, as the air currentflow slips out from indoor midair layercavity outside airdoor, it can be confirmed through Table 3 that the indoor absolute humidity have reduced by half compared to the other modes.. CONCLUSIONS This research attempted to present a solution to the problem caused by the loss of the environmental buffer space when expanding the balcony and verify it through a Mock-up experiment. 1) As a result of using the midair layercavity layer and low-e glass in the window fittings, it appeared that the insulation and condensation preventing capacity is excellent. 2) The possibility of preventing condensation indoors by lowering the absolute humidity indoors through ventilation by using the vent-slot was verified. Hereafter, an improved, rational U-value that satisfies about 9% of the outside air during the heating period (December~ February) shall be deduced by verifying the capacity of mixtures of various types of frames and fittings glasses through a simulation examination using experimental data. In addition, a plan for an outer facefacade system shall be presented for decreasing condensation and improving the insulation capacity. 189

8 Table 2. Temperature comparison of the alternative façade system (house number 2) Mode Outdoor_T Cavity_T Indoor_T Air Flow Direction Mode T Mode T Mode T Mode T Outdoor Cavity Outdoor Cavity Cavity Indoor Indoor Cavity Table 3. Comparison of absolute humidity (house number 2) Mode Outdoor_AH Cavity_AH Indoor_AH Mode Mode Mode Mode ACKNOWLEDGEMENT This research was supported by a grant(6constructioncoreb2) from Construction Core Technology Program funded by Ministry of Construction & Transportation of Korean government and was partially supported by Doosan construction & engineering Co., Ltd. REFERENCES The Ministry of Construction and Transportation Architectural division enforcement ordinance Item 1 of Para. 1 of Art. 2 and Item 4 of Para. 4 of Art. 46 provisions Jung-Min Seo, Doo-Sam Song, Sang-Ho Kim(6), Effect of the Balcony Space on Thermal Environment and Heating/Cooling Load in an House umberapartment House, The Society of Air-Conditioning and Refrigerating Engineers of Korea, pp847~83 Sang-Ho Kim, Doo-Sam Song, Effect of the Balcony on Indoor Thermal Environment and Heating/cooling Load in an House umberapartment House, Architectural Institute of Korea, KS F 2278:3, Insulation tests of fittings, 3 Hyo-Soon Park. Sung-Hee Hong, Ji-Yeon Kim, Seung-Jik, Suh, The Effect of Building Energy Rating on Balcony Remodeling in House umberapartment. Journal of the Architectural Institute of Korea, Vol. 22, No. 3, Keon-HO Lee, Hyeon-Soo Kim, Yung-Woo Ko, Young-Joo Son, Experimental Study on Natural Ventilation Performance of Double Façade System in Heating Period. Journal of the Korea Institute of Ecological Architecture and Environment, Vol. 6, No. 2,