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Investigation of a simple approach to predict rainscreen wall ventilation rates for hygrothermal simulation purposes

Falk, Jörgen LU ; Molnar, Miklos LU and Larsson, Oskar LU (2014) In Building and Environment 73(March). p.88-96
Abstract
Hygrothermal simulation programs are commonly used by design engineers to analyse moisture performance of building envelopes. For ventilated assemblies, programs typically require the user to enter cavity ventilation rates. If such input data are not prepared on physical grounds, it can impair the quality of the simulation results. In earlier papers: (1) estimations of ventilation rates in experimental walls based on cavity air velocity measurements; (2) comparative calculations based on monthly and annual tabular climate data, a simple driving force model and models of cavity airflow and heat balance, have been presented. In this study, the models and hourly climate field data were used to perform calculations of transient cavity... (More)
Hygrothermal simulation programs are commonly used by design engineers to analyse moisture performance of building envelopes. For ventilated assemblies, programs typically require the user to enter cavity ventilation rates. If such input data are not prepared on physical grounds, it can impair the quality of the simulation results. In earlier papers: (1) estimations of ventilation rates in experimental walls based on cavity air velocity measurements; (2) comparative calculations based on monthly and annual tabular climate data, a simple driving force model and models of cavity airflow and heat balance, have been presented. In this study, the models and hourly climate field data were used to perform calculations of transient cavity ventilation rates for comparison with previous experimental results. For 13 different time periods extending from 24 to 91 hours, the calculated average ventilation rates were within or very close to the experimentally estimated limits for the ventilation rate. Additionally, the calculations captured the temporal variability and the physical cause of ventilation airflow in the cavities reasonably well. The applied calculation methodology can be developed into a user friendly approach to estimate realistic ventilation rate input data for hygrothermal purposes. Limitations and possible improvements of the methodology are discussed. The influence of the accuracy and resolution of the ventilation rate input data in simulations is demonstrated in a case study. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
rainscreen wall, ventilated cavity, air change rate, ventilation rate modelling, hygrothermal simulation
in
Building and Environment
volume
73
issue
March
pages
88 - 96
publisher
Elsevier
external identifiers
  • wos:000331991700009
  • scopus:84890885926
ISSN
1873-684X
DOI
10.1016/j.buildenv.2013.11.025
language
English
LU publication?
yes
id
8e2dc4c5-8b66-4b7b-9549-96e4f2dd731c (old id 4248968)
date added to LUP
2014-01-15 15:30:57
date last changed
2017-09-24 03:13:12
@article{8e2dc4c5-8b66-4b7b-9549-96e4f2dd731c,
  abstract     = {Hygrothermal simulation programs are commonly used by design engineers to analyse moisture performance of building envelopes. For ventilated assemblies, programs typically require the user to enter cavity ventilation rates. If such input data are not prepared on physical grounds, it can impair the quality of the simulation results. In earlier papers: (1) estimations of ventilation rates in experimental walls based on cavity air velocity measurements; (2) comparative calculations based on monthly and annual tabular climate data, a simple driving force model and models of cavity airflow and heat balance, have been presented. In this study, the models and hourly climate field data were used to perform calculations of transient cavity ventilation rates for comparison with previous experimental results. For 13 different time periods extending from 24 to 91 hours, the calculated average ventilation rates were within or very close to the experimentally estimated limits for the ventilation rate. Additionally, the calculations captured the temporal variability and the physical cause of ventilation airflow in the cavities reasonably well. The applied calculation methodology can be developed into a user friendly approach to estimate realistic ventilation rate input data for hygrothermal purposes. Limitations and possible improvements of the methodology are discussed. The influence of the accuracy and resolution of the ventilation rate input data in simulations is demonstrated in a case study.},
  author       = {Falk, Jörgen and Molnar, Miklos and Larsson, Oskar},
  issn         = {1873-684X},
  keyword      = {rainscreen wall,ventilated cavity,air change rate,ventilation rate modelling,hygrothermal simulation},
  language     = {eng},
  number       = {March},
  pages        = {88--96},
  publisher    = {Elsevier},
  series       = {Building and Environment},
  title        = {Investigation of a simple approach to predict rainscreen wall ventilation rates for hygrothermal simulation purposes},
  url          = {http://dx.doi.org/10.1016/j.buildenv.2013.11.025},
  volume       = {73},
  year         = {2014},
}