scholarly journals Thermal Performance Assessment of a Wall Made of Lightweight Concrete Blocks with Recycled Brick and Ground Polystyrene

Buildings ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 584
Author(s):  
Hrvoje Krstić ◽  
Ivana Miličević ◽  
Damir Markulak ◽  
Mihaela Domazetović
Keyword(s):  
Heat Flow ◽  
Thermal Performance ◽  
Lightweight Concrete ◽  
Thermal Transmittance ◽  
Building Technology ◽  
Concrete Masonry ◽  
Concrete Blocks ◽  
U Value ◽  
Building Walls

Hollow concrete masonry blocks made of low strength self-compacting concrete with recycled crushed brick and ground polystyrene as an aggregate (RBC-EP blocks), and their expected structural role as masonry infill in steel frames, has been confirmed in previous research studies, thus the extensive investigation of thermal properties is presented in this paper to fully approve their potential application in practice. The Heat Flow and Temperature Based Method was used to conduct in-situ measurements of the wall thermal transmittance (U-value). The experimental U-values of the wall without insulation varied from 1.363 to 1.782 W/m2·K, and the theoretical value was calculated to be 2.01 W/m2·K. Thermal conductivity of the material used for making RBC-EP blocks was measured in a laboratory by using a heat flow meter instrument. To better understand the thermal performance characteristics of a wall constructed from RBC-EP blocks, a comparison with standard materials currently used and found on the market was performed. Walls constructed from RBC-EP blocks show an improvement of building technology and environmentally based enhancement of concrete blocks, since they use recycled materials. They can replace standard lightweight concrete blocks due to their desired mechanical properties, as well as the better thermal performance properties compared to commonly used materials for building walls.

scholarly journals Analysis of Convergence Characteristics of Average Method Regulated by ISO 9869-1 for Evaluating In Situ Thermal Resistance and Thermal Transmittance of Opaque Exterior Walls

Energies ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1989 ◽  
Author(s):  
Doo Sung Choi ◽  
Myeong Jin Ko
Keyword(s):  
Thermal Resistance ◽  
Average Method ◽  
Test Duration ◽  
Test Environment ◽  
Building Envelopes ◽  
Thermal Transmittance ◽  
The Third ◽  
U Value ◽  
R Value

In the last few decades, an average method which is regulated by ISO 9869-1 has been used to evaluate the in situ thermal transmittance (U-value) and thermal resistance (R-value) of building envelopes obtained from onsite measurements and to verify the validity of newly proposed methods. Nevertheless, only a few studies have investigated the test duration required to obtain reliable results using this method and the convergence characteristics of the results. This study aims to evaluate the convergence characteristics of the in situ values analyzed using the average method. The criteria for determining convergence (i.e., end of the test) using the average method are very strict, mainly because of the third condition, which compares the deviation of two values derived from the first and last periods of the same duration. To shorten the test duration, environmental variables should be kept constant throughout the test or an appropriate period should be selected. The convergence of the in situ U-value and R-value is affected more by the length of the test duration than by the temperature difference if the test environment meets literature-recommended conditions. Furthermore, there is no difference between the use of the U-value and R-value in determining the end of the test.

scholarly journals Thermal analysis and post construction verification

2019 ◽  
Vol 38 (1) ◽  
pp. 51-67
Author(s):  
Cormac Flood ◽  
Lloyd Scott
Keyword(s):  
Case Studies ◽  
Thermal Performance ◽  
Building Materials ◽  
Energy Performance ◽  
Research Project ◽  
Content Type ◽  
Thermal Transmittance ◽  
Standard Calculation

Purpose The residential sector in Ireland accounted for 25 per cent of energy related CO2 emissions in 2016 through burning fossil fuels, a major contributor to climate change. In support of Ireland’s CO2 reduction targets, the existing housing stock could contribute greatly to the reduction of space-heating energy demand through retrofit. Approximately 50 per cent of Ireland’s 2m dwellings pre-date building regulations and are predominantly of cavity and solid wall construction, the performance of which has not been extensively investigated at present. Although commitment to thermal upgrade/retrofit of existing buildings may increase under future government policies, the poor characterisation of actual thermal performance of external walls may hinder the realisation of these targets. Thermal transmittance (U-values) of exterior walls represents a source of uncertainty when estimating the energy performance of dwellings. It has been noted in research that the standard calculation methodology for thermal transmittance should be improved. Implementing current U-value calculation methods may result in misguided retrofit strategies due to the considerable discrepancies between in situ measurements and calculated wall U-values as documented in the case studies carried out in this research. If the method of hygrothermal analysis were to be employed as a replacement for the current standard calculation, it could have significant implications for policy and retrofit decision making. The paper aims to discuss this issue. Design/methodology/approach This research project analysed a case study situated in Dublin, Ireland. The case studies offer an account of the in situ thermal transmittance of exterior walls and link these to hygrothermally simulated comparisons along with more traditional design U-values. Findings The findings of this research identify discrepancies between in situ and design U-values, using measurement, hygrothermal simulation and standard method U-value calculations. The outcomes of the research serve as an introduction to issues emanating from a larger research project in order to encourage researchers to understand and further explore the topic. Originality/value It has previously been highlighted that moisture content is linked to the increase in thermal conductivity of building materials, thus reducing the thermal effectiveness and increasing the elemental U-value. Therefore, it is vital to implement reliable prediction tools to assess potential thermal performance values. This paper presents the findings of a critical instance case study in Dublin, Ireland in which an existing west facing external wall in a semi-detached dwelling was analysed, simulated and measured to verify the elemental wall assembly and quantify thermal transmittance (U-value) incorporating the major criteria required for building performance simulation.

scholarly journals Thermal Performance and Comfort Conditions Analysis of a Vernacular Palafitic Timber Building in Portuguese Coastline Context

2020 ◽  
Vol 12 (24) ◽  
pp. 10484
Author(s):  
Jorge Fernandes ◽  
Ricardo Mateus ◽  
Helena Gervásio ◽  
Sandra Monteiro Silva ◽  
Jorge Branco ◽  
...  
Keyword(s):  
Thermal Performance ◽  
Energy Demand ◽  
Energy Performance ◽  
Subjective Analysis ◽  
Heating And Cooling ◽  
Condition Evaluation ◽  
Timber Constructions ◽  
U Value ◽  
The Difference

The palafitic timber constructions of the central Portuguese coastline are an example of the adaptation to site-specific conditions (climate and sand landscape morphodynamics) using the available endogenous resources. Thus, in a context of environmental awareness and climate change, it is relevant to understand their features/strategies and how they perform. This work analyses the energy performance and thermal condition evaluation of a vernacular timber building–palheiro–from Praia de Mira, through in situ measurements, subjective analysis and energy simulation provided by DesignBuilder/EnergyPlus. The results show a good or satisfactory thermal performance during most of the seasons by passive means only. Despite, it was not possible to guarantee thermal comfort conditions for the occupants during winter. In the energy performance analysis, five scenarios, with different external walls, were compared. In the two scenarios that satisfy the maximum U-value for the climate zone, the current conventional building had a slightly better performance on heating and cooling (less 1.1 and 1.4 kWh/m2, respectively) than the timber building. However, the difference between the two construction solutions is not substantial in the annual energy demand (2.5 kWh/m2, 7.3%), indicating that timber structures are suitable in this mild climate area.

scholarly journals Comparison of Infrared Thermography and Heat Flux Method for Dynamic Thermal Transmittance Determination

Buildings ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 132 ◽  
Author(s):  
Mergim Gaši ◽  
Bojan Milovanović ◽  
Sanjin Gumbarević
Keyword(s):  
Heat Flux ◽  
Infrared Thermography ◽  
Dynamic Method ◽  
Flux Method ◽  
Microsoft Excel ◽  
Experimental Procedure ◽  
Thermal Transmittance ◽  
U Value ◽  
Stationary Heat Transfer

This paper proposes an alternative experimental procedure that uses infrared thermography (IRT) for measuring the surface temperature of building elements, through which it is possible to approximate the thermal transmittance or the U-value. The literature review showed that all authors used similar procedures that require semi-stationary heat transfer conditions, which, in most cases, could not be achieved. The dynamic and the average methods that are given in ISO 9869 were also used with the IRT and the heat flux method (HFM). The dynamic method (DYNM) shows a higher level of accuracy compared to the average method (AVGM). Since the algorithm of the DYNM is more complicated than that of the AVGM, Microsoft Excel VBA was used to implement the algorithm of the DYNM. Using the procedure given in this paper, the U-value could be approximated within 0–30% of the design U-value. The use of IRT, in combination with the DYNM, could be used in-situ since the DYNM does not require stable boundary conditions. Furthermore, the procedure given in this paper could be used for relatively fast and inexpensive U-value approximation without the use of expensive equipment (e.g., heat flux sensors).

scholarly journals Influence of HFM Thermal Contact on the Accuracy of In Situ Measurements of Façades’ U-Value in Operational Stage

2021 ◽  
Vol 11 (3) ◽  
pp. 979
Author(s):  
Katia Gaspar ◽  
Miquel Casals ◽  
Marta Gangolells
Keyword(s):  
Heat Flow ◽  
Thermal Contact ◽  
Accurate Information ◽  
Wall Surface ◽  
Flow Meter ◽  
Usual Procedure ◽  
Pvc Film ◽  
U Value ◽  
Heat Flow Meter

Accurate information on the actual thermal transmittance of walls is vital to select appropriate energy-saving measures in existing buildings to meet the commitments of the European Green Deal. To obtain accurate results using the heat flow meter (HFM) method, good thermal contact must be made between the heat flow meter plate and the wall surface. This paper aimed to assess the influence of the non-perfect thermal contact of heat flow meter plates on the accuracy of in situ measurement of the façades’ U-value when a film was applied to avoid damage to the wall surface. Given the fact that to avoid harm to the wall surface, the laying of a film is a usual procedure in the installation of equipment during the building’s operational stage. The findings show that deviations between measured U-values when an HFM was installed directly on the wall surface and when an HFM was installed with a PVC film were found to differ significantly from the theoretical effect of including a PVC film during the monitoring process.

scholarly journals Properties of lightweight concrete blocks with waste zeolitic tuff

2020 ◽  
Vol 26 (4) ◽  
pp. 463-470
Author(s):  
Ilker TEKIN ◽  
Turkay KOTAN ◽  
Allison T. OSMANSON ◽  
Witold BROSTOW ◽  
Osman GENCEL ◽  
...  
Keyword(s):  
Water Absorption ◽  
Lightweight Concrete ◽  
Unit Weight ◽  
Zeolitic Tuff ◽  
Capillary Water ◽  
Chemical Additive ◽  
Concrete Masonry ◽  
Different Types ◽  
Concrete Blocks ◽  
Aerated Concrete

In general, three different types of wall products commonly used in the building sector, namely traditional clay brick, lightweight concrete blocks and aerated concrete, are produced with pumice and perlite. We have created alternative block walls with Bayburt stone (BS) containing zeolite, namely lightweight concrete masonry blocks (LCMBs). BS was an aggregate, cement dosages ranging from 150 to 250 kg/m3 were a binder, 3 different type of superplasticizers were selected as a chemical additive. Compressive strength, water absorption, unit weight, elevated heat effect, freeze-thaw resistance, capillary water absorption and thermal conductivity tests were performed.

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