Comparison between Glaser Method and Heat, Air and Moisture Transient Model for Moisture Migration in Building Envelopes

2019 ◽  
Vol 887 ◽  
pp. 385-392 ◽  
Author(s):  
Michele Libralato ◽  
Onorio Saro ◽  
Alessandra de Angelis ◽  
Simone Spinazzè
Keyword(s):  
Moisture Content ◽  
Material Properties ◽  
Moisture Transfer ◽  
Building Envelope ◽  
Assessment Procedure ◽  
Moisture Migration ◽  
Building Envelopes ◽  
Transient Model ◽  
Percentage Difference ◽  
Real Phenomenon

The Glaser method is an assessment procedure for the risk of moisture accumulation in building mono-dimensional structures, that could be used to evaluate mould risk and interstitial condensation risk.It is based on a simplified model that does not represent the real phenomenon and its limitations are well-known qualitatively.This work provides a comparison in terms of moisture content between the Glaser method and WUFI Pro, an advanced heat, air and moisture transfer prediction tool. First the influence of material properties is evaluated on four fictitious materials walls, then six different building envelope typologies for six weather files from Central and Southern Europe are modelled to evaluate the Glaser method results.The effects of the Glaser method simplifications are quantified in terms of moisture content percentage difference.

Positive pressure effect on moisture performance in a school building

2019 ◽  
Vol 43 (2) ◽  
pp. 121-142
Author(s):  
Andrea Ferrantelli ◽  
Camilla Vornanen-Winqvist ◽  
Milla Mattila ◽  
Heidi Salonen ◽  
Jarek Kurnitski
Keyword(s):  
Air Quality ◽  
Moisture Content ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
Moisture Transfer ◽  
Building Envelope ◽  
Positive Pressure ◽  
School Building ◽  
Negative Effects ◽  
Moisture Performance

Moisture excess in buildings constitutes a complex problem affecting indoor air quality, energy consumption and the lifetime of the building envelope. We investigate the effect on moisture transfer in structures as a positive pressure is applied inside the enclosure. It is found that, contrary to established belief, the positive pressure does not induce any negative effects on the structures’ moisture content in normally ventilated classrooms, even with high occupancy. Our case study consists of a school building in Finland, subject to temperature and relative humidity measurements after a small (5–7 Pa) positive pressure was realized through ventilation control. We first address analytically the moisture excess generated inside the classrooms for 14 days, using dynamical balance equations that account for both ventilation effects and occupants’ moisture release in the environment. It is found that the average moisture excess is very small, largely below 1 g/m3, even for ventilation rates that are half the design value. We also examine the moisture performance of the envelope, by addressing the moisture migration at upper and lower joints of the external walls for both measured and design values of the indoor absolute humidity (AH). A coupled numerical model of diffusion and convection shows that moisture accumulation in the envelope and the according stresses are negligible for any realistic AH values. This result is in agreement with field measurements at the school. In conclusion, it seems that applying a small overpressure in a well-ventilated school building during a standard service period resulted in no accumulation inside the external walls, even at high occupancy and with low ventilation. Remarkably, it slightly dried out the moisture content in structures under actual occupancy conditions. The positive pressure has accordingly no negative effects on moisture performance, and is capable to guarantee a good indoor air quality as well.

scholarly journals Simulation Research on the Effect of Coupled Heat and Moisture Transfer on the Energy Consumption and Indoor Environment of Public Buildings

Energies ◽  
2019 ◽  
Vol 12 (1) ◽  
pp. 141 ◽  
Author(s):  
Shui Yu ◽  
Yumeng Cui ◽  
Yifei Shao ◽  
Fuhong Han
Keyword(s):  
Energy Consumption ◽  
Indoor Environment ◽  
Moisture Transfer ◽  
Building Envelope ◽  
Thermal Calculation ◽  
Heat And Moisture Transfer ◽  
Building Envelopes ◽  
Coupled Heat And Moisture ◽  
Heat And Moisture ◽  
Humidity Environment

A building envelope is a multi-layer porous structure. It transfers heat and moisture to balance the indoor and outdoor temperature difference and water vapor partial pressure difference. This is a typical coupled heat and moisture migration process. When the space is filled with moist air, water or ice, it will directly affect the thermal properties of the material. With respect to moisture coming through the wall into the indoor building, it will also affect the indoor environment and the energy consumption due to the formation of latent heat. However, the moisture transfer process in the building envelopes is not taken into account in the current conventional thermal calculation and energy consumption analysis. This paper analyzes the indoor thermal and humidity environment and building energy consumption of typical cities in Harbin, Shenyang, Beijing, Shanghai, and Guangzhou. The results show that it is obvious that the coupled heat and moisture transfer in the building envelopes has an impact on the annual cooling and heating energy consumption, the total energy consumption, and the indoor thermal and humidity environment. The geographical location of buildings ranging from north to south influences the effect of coupled heat and moisture transfer on the annual energy consumption of the building, moving from positive to negative. It is suggested that the additional coefficient of the coupled thermal and moisture method can effectively correct the existing energy consumption calculation results, which do not take the consumption from the coupled heat and moisture in the building envelopes into account.

scholarly journals Modeling of Coupled Heat and Mass Transfers in a Stabilized Earthen Building Envelope with Thatched Fibers

Fibers ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 75
Author(s):  
Madeleine Nitcheu ◽  
Donatien Njomo ◽  
Pierre Meukam ◽  
Cyrille Fotsing Talla
Keyword(s):  
Moisture Content ◽  
Building Materials ◽  
Numerical Solutions ◽  
Moisture Transfer ◽  
Building Envelope ◽  
One Dimensional ◽  
Composites Materials ◽  
Model Equations ◽  
Mass Transfers ◽  
Heat And Moisture

In order to reduce the heat and mass transfers in buildings, which increase energy bills, the development of composites materials such as earth bricks stabilized with thatch fibers is important for their construction. This paper aims to study a one-dimensional model of heat and moisture transfer through porous building materials. The coupled phenomena of heat and mass transfer are described by the Luikov model. Equations and boundary conditions are discretized using the finite difference method. The results obtained illustrate the temporal evolutions of the temperature and the moisture content, as well as the distributions of the temperature and moisture content inside the wall. The profile of the temperature and water content that are obtained are compared with the other numerical solutions that are available in the literature.

scholarly journals Application Method of a Simplified Heat and Moisture Transfer Model of Building Construction in Residential Buildings

Energies ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4180
Author(s):  
Joowook Kim ◽  
Michael Brandemuehl
Keyword(s):  
Latent Heat ◽  
Moisture Transfer ◽  
Residential Buildings ◽  
Building Energy ◽  
The United States ◽  
Building Envelope ◽  
Outdoor Environment ◽  
Transfer Model ◽  
Heat And Moisture Transfer ◽  
Heat And Moisture

Several building energy simulation programs have been developed to evaluate the indoor conditions and energy performance of buildings. As a fundamental component of heating, ventilating, and air conditioning loads, each building energy modeling tool calculates the heat and moisture exchange among the outdoor environment, building envelope, and indoor environments. This paper presents a simplified heat and moisture transfer model of the building envelope, and case studies for building performance obtained by different heat and moisture transfer models are conducted to investigate the contribution of the proposed steady-state moisture flux (SSMF) method. For the analysis, three representative humid locations in the United States are considered: Miami, Atlanta, and Chicago. The results show that the SSMF model effectively complements the latent heat transfer calculation in conduction transfer function (CTF) and effective moisture penetration depth (EMPD) models during the cooling season. In addition, it is found that the ceiling part of a building largely constitutes the latent heat generated by the SSMF model.

scholarly journals Identification of heat and mass transfer processes in bread during baking

2005 ◽  
Vol 9 (2) ◽  
pp. 73-86 ◽  
Author(s):  
Ivanka Zheleva ◽  
Vesselka Kambourova
Keyword(s):  
Partial Differential Equations ◽  
Moisture Content ◽  
Differential Equations ◽  
Moisture Transfer ◽  
Partial Differential ◽  
Linear Partial Differential Equations ◽  
Mass Transfer Processes ◽  
Model Equations ◽  
Heat And Moisture ◽  
Simultaneous Heat

A mathematical model representing temperature and moisture content in bread during baking is developed. The model employs the coupled partial differential equations proposed by Luikov. Dependences of mass and thermal properties of dough on temperature and moisture content are included in the model. Resulting system of non-linear partial differential equations in time and one space dimension is reduced to algebraic system by applying a finite difference numerical method. A numerical solution of the model equations is obtained and simultaneous heat and moisture transfer in dough during baking is predicted. The changes of temperature and moisture content during the time of the process are graphically presented and commented.

scholarly journals A Comparison Of Building Envelope Performance Levels Between Ontario, Denmark, Germany And The Passive House Standard, In The Low-Rise, Residential Context

2021 ◽  
Author(s):  
Blaine Attwood
Keyword(s):  
Energy Use ◽  
Building Envelope ◽  
Passive House ◽  
Building Envelopes ◽  
Residential Sector ◽  
Greater Toronto Area ◽  
Residential Context ◽  
Minimum Requirements ◽  
Other World ◽  
House Standard

This research compared and analyzed where the Ontario Building Code rates in the low-rise, residential sector in terms of its: in comparison to Denmark, Germany and the Passive House Standard. This was analyzed to see how Ontario compared against other world renowned energy efficient regulations and where or if there was room for improvement. For this, HOT2000 and THERM were utilized on all four of the reference standards, where both of these programs were managed in a way to compare the results of ‘typical’ building envelopes and the current regulation from each of the standards. These results were then able to provide a whole home’s heating and air conditioning energy use in the Greater Toronto Area climate. Overall, the results illustrated Ontario homes consume the most energy for both typically constructed homes and homes utilizing the minimum requirements. In addition to this, Ontario also had the least performing building envelope connection details. In total, the Passive House performed at the highest level followed by Germany, Denmark and then Ontario.

scholarly journals Influence of airtightness of steel sandwich panel joints on heat losses

2020 ◽  
Vol 172 ◽  
pp. 05008
Author(s):  
Markus Kuhnhenne ◽  
Vitali Reger ◽  
Dominik Pyschny ◽  
Bernd Döring
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Building Envelope ◽  
The Finite Element Method ◽  
Transmission Losses ◽  
Building Envelopes ◽  
Metal Building ◽  
Effective Heat Transfer Coefficient ◽  
The Heat Transfer Coefficient

Energy saving ordinances requires that buildings must be designed in such a way that the heat transfer surface including the joints is permanently air impermeable. The prefabricated roof and wall panels in lightweight steel constructions are airtight in the area of the steel covering layers. The sealing of the panel joints contributes to fulfil the comprehensive requirements for an airtight building envelope. To improve the airtightness of steel sandwich panels, additional sealing tapes can be installed in the panel joint. The influence of these sealing tapes was evaluated by measurements carried out by the RWTH Aachen University - Sustainable Metal Building Envelopes. Different installation situations were evaluated by carrying out airtightness tests for different joint distances. In addition, the influence on the heat transfer coefficient was also evaluated using the Finite Element Method (FEM). The combination of obtained air volume flow and transmission losses enables to create an "effective heat transfer coefficient" due to transmission and infiltration. This summarizes both effects in one value and is particularly helpful for approximate calculations on energy efficiency.

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