Description
This paper draws key points of hygrothermal simulation and modeling from a recently commissioned study by Historic Scotland to evaluate insulation retrofit strategies for their traditional building stock. Insulation retrofits on walls can help conserve energy and make the building more sustainable and comfortable for occupants. However, if done without proper assessment and care, the works may result in moisture accumulation, interstitial condensation, deterioration and dangerous mold growth. Heavy solid masonry walls, common in historic buildings, pose a particular challenge to safely retrofit. The hygroscopic nature of these walls requires complex analysis to properly assess the performance impact of the retrofit. The paper compares two hygrothermal assessment methods: dew-point assessment and numerical simulation. These methods both have governing international standards in effect, ISO 13788:2012 and BS EN 15026:2007 respectively. Unfortunately, there is a lack of industry understanding on the limitations of the dew-point method and its ease of use continues to make it a popular and accepted method of assessment. This paper first outlines the limitations of the dew-point method and shows how the inappropriate use of this assessment tool can give distinctly misleading results when assessing hygrothermal performance and risk. The paper then focuses on guidance for modeling techniques to more accurately evaluate performance by numerical simulation. Topics include (i) the challenges of unknown material properties; (ii) establishing the baseline time-dependent, non-homogeneous and non-linear initial conditions within the existing structure, and (iii) reasonable simplifications for modelling the non-homogeneous stone and mortar composition of historic solid walls. The complete report for this study, including a much more in-depth discussion of the building physics, hygrothermal performance and a case study hygrothermal evaluation of 13 different retrofit options has been published by Historic Scotland as Technical Paper 15.
Citation: ASHRAE Papers: 2015 ASHRAE Annual Conference, Atlanta, GA
Product Details
- Published:
- 2015
- Number of Pages:
- 8
- Units of Measure:
- Dual
- File Size:
- 1 file , 2.6 MB
- Product Code(s):
- D-AT-15-C012
