STUDY ON HYGROTHERMAL BEHAVIOR OF WALL ASSEMBLY WITH VENTED CAVITY IN CONSIDERATION OF DRIVING RAIN (PART1): IMPACT OF RAIN PENETRATION AND WATER ABSORPTION OF EXTERIOR SYSTEM ON HYGROTHERMAL BEHAVIOR WITHIN WALL ASSEMBLY

The wall assembly with vented cavity using the siding is installed for durable improvement in many wooden houses. The houses with less projected eaves built on very narrow and small properties are increasing in recent years. According to an investigation of moisture damage by authors, many of houses...

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Veröffentlicht in:Journal of Environmental Engineering (Transactions of AIJ) 2020, Vol.85(767), pp.19-28
Hauptverfasser: OSAMURA, Sadaharu, SAITO, Hiroaki, NAKAJIMA, Masao
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Sprache:jpn
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Zusammenfassung:The wall assembly with vented cavity using the siding is installed for durable improvement in many wooden houses. The houses with less projected eaves built on very narrow and small properties are increasing in recent years. According to an investigation of moisture damage by authors, many of houses which internal condensation occurs were built in less than ten years. Deteriorated siding and joints in these houses have potential for water absorption and rain penetration. It is considered that these accumulated moisture have significant impact to cause the internal condensation within stud cavity, when surface temperature on the siding raises by solar radiation. However there are few studies regarding hygrothermal behavior in consideration of these impacts such as water absorption and rain penetration at outside finishings. To unravel mechanism of the internal condensation due to moisture cause the rain water, lab-experiments and field measurements were conducted. In the lab-experiments, water penetration rate and water absorption coefficient of sidings were quantitated. In the field measurement, the internal condensation was reproduced by intermittent injection of rain water into the vented cavity. Additionally, the drying performance of different ventilation configurations were compared by humidity and moisture content variations within wall assemblies in field measurements. The findings of the study are as follows; (1) Quantity of rain penetration form siding joints : Quantity of rain penetration from siding joints of four installation methods were measured by water spray test. It was confirmed that there were significant differences in the amount of water penetration between the installation methods. In the cases which condensation occurred, the water penetration rate was 5 to 12 % at low wind speed. From the result, it is considered that intermittent rain penetration occurs with high frequency in rainy day. (2) Water absorption test from siding surfaces : Quantity of water absorption of siding with chalking and sound one just after the testing are 0.62 kg/m2 and 0.06 kg/m2 respectively. This result is suggested that the quantity of absorption water increased with deterioration of the surface coating due to aging. In addition, since water was absorbed just after water absorption, it is considered that water is absorbed and retained every time it rains. (3) Impact of rain penetration and water absorption of exterior system on hygrothermal behavior within
ISSN:1348-0685
1881-817X
DOI:10.3130/aije.85.19