Benefits of Investigating the Thermal Component for Moisture Safety in Ventilated Attics

Forskningsoutput: Kapitel i bok/rapport/Conference proceedingKonferenspaper i proceeding

Standard

Benefits of Investigating the Thermal Component for Moisture Safety in Ventilated Attics. / Claesson, Johan; Wallentén, Petter.

12th Nordic Symposium on Building Physics (NSB 2020). Vol. 172 2020. 23001 (E3S Web of Conferences).

Forskningsoutput: Kapitel i bok/rapport/Conference proceedingKonferenspaper i proceeding

Harvard

Claesson, J & Wallentén, P 2020, Benefits of Investigating the Thermal Component for Moisture Safety in Ventilated Attics. i 12th Nordic Symposium on Building Physics (NSB 2020). vol. 172, 23001, E3S Web of Conferences, 12th Nordic Symposium on Building Physics, NSB 2020, Tallinn, Estland, 2020/09/06. https://doi.org/10.1051/e3sconf/202017223001

APA

Claesson, J., & Wallentén, P. (2020). Benefits of Investigating the Thermal Component for Moisture Safety in Ventilated Attics. I 12th Nordic Symposium on Building Physics (NSB 2020) (Vol. 172). [23001] (E3S Web of Conferences). https://doi.org/10.1051/e3sconf/202017223001

CBE

Claesson J, Wallentén P. 2020. Benefits of Investigating the Thermal Component for Moisture Safety in Ventilated Attics. I 12th Nordic Symposium on Building Physics (NSB 2020). Article 23001. (E3S Web of Conferences). https://doi.org/10.1051/e3sconf/202017223001

MLA

Vancouver

Claesson J, Wallentén P. Benefits of Investigating the Thermal Component for Moisture Safety in Ventilated Attics. I 12th Nordic Symposium on Building Physics (NSB 2020). Vol. 172. 2020. 23001. (E3S Web of Conferences). https://doi.org/10.1051/e3sconf/202017223001

Author

Claesson, Johan ; Wallentén, Petter. / Benefits of Investigating the Thermal Component for Moisture Safety in Ventilated Attics. 12th Nordic Symposium on Building Physics (NSB 2020). Vol. 172 2020. (E3S Web of Conferences).

RIS

TY - GEN

T1 - Benefits of Investigating the Thermal Component for Moisture Safety in Ventilated Attics

AU - Claesson, Johan

AU - Wallentén, Petter

PY - 2020

Y1 - 2020

N2 - 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.

AB - 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.

U2 - 10.1051/e3sconf/202017223001

DO - 10.1051/e3sconf/202017223001

M3 - Paper in conference proceeding

AN - SCOPUS:85088456730

VL - 172

T3 - E3S Web of Conferences

BT - 12th Nordic Symposium on Building Physics (NSB 2020)

T2 - 12th Nordic Symposium on Building Physics, NSB 2020

Y2 - 6 September 2020 through 9 September 2020

ER -