Benefits of Investigating the Thermal Component for Moisture Safety in Ventilated Attics
Claesson, Johan LU and Wallentén, Petter LU
(2020)
12th Nordic Symposium on Building Physics, NSB 2020
In E3S Web of Conferences
172.
- Abstract
Cold ventilated attics often have mould problems in Sweden. This is valid both for old and sometimes newly built attics. Increased insulation on the attic floor is assumed to increase the problem. To investigate this, numerical 1D models like WUFI or WUFI+ are typically used. These models give results but the physical processes are not so transparent for the user due to the complex numerical techniques involved and takes a long time to simulate. The problem is mainly related to the temperature in the attic, the ventilation rate and possible of leaks from the living space. All exposed surfaces in the attic will buffer moisture variations. But if this buffering is neglected and the leakage is treated as a constant the moisture content in... (More)
Cold ventilated attics often have mould problems in Sweden. This is valid both for old and sometimes newly built attics. Increased insulation on the attic floor is assumed to increase the problem. To investigate this, numerical 1D models like WUFI or WUFI+ are typically used. These models give results but the physical processes are not so transparent for the user due to the complex numerical techniques involved and takes a long time to simulate. The problem is mainly related to the temperature in the attic, the ventilation rate and possible of leaks from the living space. All exposed surfaces in the attic will buffer moisture variations. But if this buffering is neglected and the leakage is treated as a constant the moisture content in the attic is only dependent on the ventilation with outside air and the assumed leakage. This would make a pure thermal investigation meaningful. An analytical model for the thermal problem was developed that took into account radiation between the interior surfaces and the different boundary conditions at the outside and inside surfaces. Using this model a parameter study of exterior roofing insulation was done using a moisture transport model that only took into account convection exchange. The results were compared with WUFI Pro and WUFI+ simulations which included the moisture exchange between air and internal surfaces. The comparison showed that the pure thermal model gave, as expected, larger variations in relative humidity, but that the results were qualitatively very similar. This indicates that analytical solutions of thermal problems can be used as a base in qualitative investigations of certain combined heat and moisture problems.
(Less)
- author
- Claesson, Johan
LU
and Wallentén, Petter
LU
- organization
- publishing date
- 2020
- type
- Chapter in Book/Report/Conference proceeding
- publication status
- published
- subject
- host publication
- 12th Nordic Symposium on Building Physics (NSB 2020)
- series title
- E3S Web of Conferences
- volume
- 172
- article number
- 23001
- conference name
- 12th Nordic Symposium on Building Physics, NSB 2020
- conference location
- Tallinn, Estonia
- conference dates
- 2020-09-06 - 2020-09-09
- external identifiers
-
- scopus:85088456730
- ISSN
- 2555-0403
- DOI
- 10.1051/e3sconf/202017223001
- language
- English
- LU publication?
- yes
- id
- d857a266-9e75-48ba-85f8-0c9e656f8972
- date added to LUP
- 2020-08-05 07:52:56
- date last changed
- 2022-04-19 00:07:51
@inproceedings{d857a266-9e75-48ba-85f8-0c9e656f8972,
abstract = {{<p>Cold ventilated attics often have mould problems in Sweden. This is valid both for old and sometimes newly built attics. Increased insulation on the attic floor is assumed to increase the problem. To investigate this, numerical 1D models like WUFI or WUFI+ are typically used. These models give results but the physical processes are not so transparent for the user due to the complex numerical techniques involved and takes a long time to simulate. The problem is mainly related to the temperature in the attic, the ventilation rate and possible of leaks from the living space. All exposed surfaces in the attic will buffer moisture variations. But if this buffering is neglected and the leakage is treated as a constant the moisture content in the attic is only dependent on the ventilation with outside air and the assumed leakage. This would make a pure thermal investigation meaningful. An analytical model for the thermal problem was developed that took into account radiation between the interior surfaces and the different boundary conditions at the outside and inside surfaces. Using this model a parameter study of exterior roofing insulation was done using a moisture transport model that only took into account convection exchange. The results were compared with WUFI Pro and WUFI+ simulations which included the moisture exchange between air and internal surfaces. The comparison showed that the pure thermal model gave, as expected, larger variations in relative humidity, but that the results were qualitatively very similar. This indicates that analytical solutions of thermal problems can be used as a base in qualitative investigations of certain combined heat and moisture problems.</p>}},
author = {{Claesson, Johan and Wallentén, Petter}},
booktitle = {{12th Nordic Symposium on Building Physics (NSB 2020)}},
issn = {{2555-0403}},
language = {{eng}},
series = {{E3S Web of Conferences}},
title = {{Benefits of Investigating the Thermal Component for Moisture Safety in Ventilated Attics}},
url = {{http://dx.doi.org/10.1051/e3sconf/202017223001}},
doi = {{10.1051/e3sconf/202017223001}},
volume = {{172}},
year = {{2020}},
}