Interstitial Condensation Risk Report. MASONRY WALL WITH POLASTIC Queanbeyan

Transcription

1 Interstitial Condensation Risk Report Prepared by: Gradwell Consulting ABN Sustainability Consultants PO Box 4 Pymble NSW 2073 t: e: info@gradwellconsulting.com w:

2 Table of Contents 1 Background Disclaimer Construction Scenario Results of Risk Analysis Summary...4 Appendix File: Condensation Risk Report PT1 Masonry Wall Page 2 of 5

3 1 Background The increased focus on energy efficiency has resulting in better insulated and sealed buildings. However these improvements can also increase the risk of condensate forming in walls, roofs and ceilings. The risk of interstitial condensation forming at the interfaces of layers within an element can be assessed by software that calculates the internal surface temperatures and moisture content. The likelihood of condensation forming within a building element depends upon the hygrothermic properties of the materials (thermal conductivity or resistance and vapour resistivities or resistance) and the environmental conditions (internal and external temperatures and relative humidities). The method of analysis is as set out in EN ISO 13788: This method assumes that the temperature distribution in each layer is linear (steady state conditions). 2 Disclaimer This report assesses the likelihood of condensation occurring based on the method outlined in EN ISO The assumptions used in the analysis are stated in this report. Factors such as the actual installation of the materials, variation in the material properties, actual climatic conditions, internal temperatures and humidity and limitations in the method mean that no guarantee can be made that condensate will not form. 3 Construction Scenario This report assesses the risk of interstitial condensation in a masonry wall with 16 mm Polastic insulation and 13 mm plasterboard on studs located in the Canberra climate zone for an "average" year. No analysis is included for a "worse case" year. The internal humidity class is a dwelling with low occupancy (class 3). The internal temperature is 20 o C. The material properties of the 200 mm concrete wall and 13 mm gypsum plasterboard are based on the standard library. The thermal conductivity and vapour resistance of 16 mm Polastic are based on AWTA test results provided by Proactive Technology Australia. The thermal resistance of the reflective airspace is based on BCA2012 Specification J1.2 Material Properties 2(c) and verified using the R-Gap calculator in BERS Pro Plus. 1 EN ISO 13788:2002 Hygrothermic performance of building components and building elements - Internal surface temperature to avoid critical surface humidity and interstitial condensation - Calculation methods. File: Condensation Risk Report PT1 Masonry Wall Page 3 of 5

4 4 Results of Risk Analysis With "average" climate, the analysis predicts that no interstitial condensation will occur. Refer to Appendix 1 for a detailed report and dew point graph for the "average" climate conditions. 5 Summary No interstitial condensation is predicted in an average year. File: Condensation Risk Report PT1 Masonry Wall Page 4 of 5

5 Appendix 1 This report summarises the results for an "average" climate. The table summarises the dew point and dry bulb interface temperatures and the ISO prediction of monthly and accumulated condensation. The graph shows the dew point (blue broken line) and interface (red solid line) temperatures. Condensation is predicted to occur when the lines converge. File: Condensation Risk Report PT1 Masonry Wall Page 5 of 5