Thermal Bridging and Linear Thermal Transmittance Calculations for Balconies

The purpose of this work was to quantify the thermal bridge effect of vertical diagonal tie connectors in precast concrete sandwich panels (PCSPs). Special interest was in cases where the use of rigid insulation (e.g. PIR) would leave air gaps between insulation boards and diagonal ties, thus intensifying the thermal bridge. A climate chamber experiment using 5 different joint types was performed to gather reference data for CFD model validation. In the experiment, natural convection was observed in joints where no additional insulation was used, i.e. in air cavities. Significantly larger heat fluxes were measured in these cavities compared to insulated joints. The thermal bridging effect was evaluated for a typical PCSP (thermal transmittance without thermal bridges U = 0.11 W/(m²·K)) using CFD software taking into account 3D heat conduction and convection. Simulation results indicate that diagonal ties without adjacent air cavities increased the average thermal transmittance (U-value) of the envelope by 8%, diagonal ties with a 6 mm air cavity – 19...33% and diagonal ties with a 10 mm air cavity – 45...56%. In conclusion, it was found that the joints in insulation caused by diagonal ties affect the overall thermal performance of the building envelope significantly when efforts are not made to fill the air cavities around the connectors.

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Research on Amending the Energy Efficiency Provisions in the Building

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.568-570.1991 ◽

2014 ◽

Vol 568-570 ◽

pp. 1991-1994

Author(s):

Hai Hong Cui

Keyword(s):

Energy Performance ◽

Hot Water ◽

Building Regulations ◽

Thermal Transmittance ◽

Energy Performance Of Buildings ◽

Air Tightness ◽

Thermal Bridging ◽

Technical Basis ◽

Fuel Costs

The purpose of this paper is to identify the main requirements of the Building Regulations Part L1A for new dwellings. An explanation of the technical basis for energy rating is given including how they are calculated, how fuel costs are used, the role of the standard occupancy pattern, and an appreciation of the Building Research Establishment Domestic Energy Model (BREDEM). The aims and requirements of the European Directive on the Energy performance of Buildings and its implementation for new and existing domestic buildings is also considered. Design/methodology/approach – The requirements of Part L1A of the Building Regulations are developed. These relate to the thermal properties of the building fabric including insulation, thermal bridging, air tightness and glazing, the efficiency and responsiveness of heating and hot water systems, ventilation and lighting. The methodology for calculating thermal transmittance coefficients (U-values) is also demonstrated.

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Development of Psi Factors for Thermal Bypass Due to Insulation Gaps in Low-Slope Roofing Assemblies

Buildings ◽

10.3390/buildings12010068 ◽

2022 ◽

Vol 12 (1) ◽

pp. 68

Author(s):

Sudhakar Molleti ◽

David van Reenen

Keyword(s):

Research Study ◽

Measured Data ◽

Dimensional Changes ◽

Thermal Transmittance ◽

Average Decrease ◽

R Value ◽

Thermal Bridging ◽

Gap Height ◽

Roof Design ◽

Gap Width

In commercial roofs, the presence or formation of gaps could be due to improper installation, thermal expansion, and dimensional changes in the insulation boards. The heat loss from these gaps could lead to higher thermal transmittance in the roof assembly. The current research study conducted around 70 experiments to investigate the effect of gap height, gap width and gap offset on the thermal transmittance of the roofing assembly. The measured data showed that in a staggered insulation layout with a joint offset of 610 mm (24 in), formation of 6.4 mm (1/4 in) to 12.7 mm (1/2 in) gaps at the insulation joints could contribute to an average decrease of 2% to 9% in the effective R-value of the roof assembly. As the insulation thermal resistance increases or becomes thicker, the thermal losses in the roof assembly increase. Generalized gap impact curves were developed to provide the relation between gap parameters (i.e., gap widths and height) and the thermal performance of the roof assembly. The experimental data were further analyzed using the psi factor approach of linear thermal bridging generating thermal transmittance data to support the calculation of thermal bypass from gaps in the thermal roof design.

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