Condensation in Buildings - Australian Building Codes Board

More documents

Recommendations

Info

Information Handbook: Condensation in Buildings climate classifications. Any attempt at alignment quickly reveals significant mismatching on one criterion or another. Many US locations, for example, have a mean annual outdoor temperature substantially cooler than the average outdoor dew point temperature in one of more months (Lstiburek 2011). This situation is rare in Australian climates. A basic benchmark to note, however, is that one of Australia’s coldest climates, Thredbo, fits into the IECC Cold climate category (zone 6 in Figure 4.5) by having an annual heating requirement of about 4,900 Heating Degree Days (HDD to base 18°C). The qualifying range for IECC zone 6 is 3,000 to 5,000 HDD. Figure 4.6 – Australian land mass overlaid on the contiguous United States at equivalent latitudes (The side-to-side placement provides an approximate alignment of moist and dry regions.) DRAFT HANDBOOK Although latitude alone does not account for climatic similarities, the true-to-scale comparison of the Australian and US maps in Figure 4.6shows that the maps overlap mainly in regions designated in the United States as Hot or Mixed climates (Humid on the east and Dry on the west). Australia's greater latitude span (33° compared to 25° or a distance of about 900 km) and its closer proximity to the Equator (10° rather than 25°) tend to extend the meaning of the terms "Hot" and "Humid". In any case, systematic classification of climates needs to be matched by consensus on indoor and outdoor conditions to be applied in risk calculation methods. Current calculation methods and software tools are very sensitive to the assumed environmental conditions. For the US, Australian Building Codes Board Page 35
Information Handbook: Condensation in Buildings ASHRAE Standard 160-2009 (outlined in Chapter 6) offers, according to its title, “Criteria for Moisture-Control Design Analysis in Buildings”, to provide a consistent framework for design assumptions or assumed loads. Noting the lack of similar information for Australian conditions, Dr Richard Aynsley (2012a), Building Energetics Pty Ltd, suggests that “Australia needs a standard on moisture control in buildings that reflects the huge span of latitude of the country. Without an Australian standard for assessing condensation risk, there is no consensus on what are appropriate input data, hygrothermal analysis methods, or evaluation of results”. 4.3 Comparing Outdoor Condensation Potential across Australia Without an established consensus, Australian building practitioners may still find useful information in local resources. Figure 4.7, for example, uses some of the information available in monthly climate statistics provided online by the BOM to highlight the potential for condensation under outdoor conditions. The necessary information is available for numerous Australian locations. Figure 4.7 – Comparison of monthly mean minimum temperatures and average dew points (outdoor condensation potential) 35°C Mean Maximum Temperature 30°C 25°C 20°C 15°C Average Outdoor Dew Point 10°C 5°C Richmond (NSW) Mean Minimum Temperature falls below Average Dew Point from April to August Mean Minimum Temperature DRAFT HANDBOOK 0°C Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Outdoor Condensation Potential The BOM statistics provide (among other details) mean minimum and mean maximum temperatures for each month, averaged over the number of years available for each weather Australian Building Codes Board Page 36
Page 1 and 2: CONDENSATION IN BUILDINGS INFORMATI
Page 3 and 4: Information Handbook: Condensation
Page 41: Information Handbook: Condensation
Page 93 and 94:
Information Handbook: Condensation
Page 95 and 96:
Page 97 and 98:
Page 99 and 100:
Page 101 and 102:
Page 103 and 104:
Page 105 and 106:
Page 107 and 108:
Page 109 and 110:
Page 111 and 112:
Page 113 and 114:
show all

Condensation in Buildings - Australian Building Codes Board

Create successful ePaper yourself

Delete template?

Save as template?