scholarly journals In-situ measurements of the U-value of a ventilated wall assembly

2021 ◽  
Vol 2069 (1) ◽  
pp. 012212
Author(s):  
M Rahiminejad ◽  
D Khovalyg
Keyword(s):  
National Level ◽  
Performance Standards ◽  
Energy Performance ◽  
Building Envelope ◽  
Wall Structure ◽  
Thermal Transmittance ◽  
Ventilated Cavity ◽  
Air Space ◽  
U Value ◽  
Wall Assembly

Abstract The walls in a building envelope have the largest contact area with the exterior environment, and, therefore, a considerable portion of the thermal energy can be lost through the walls compared to the other parts of the building envelope. For energy-saving purposes, the thermal transmittance of walls is typically limited by building energy performance standards at the national level. However, the presence of a ventilated air-space behind the external cladding, which has variable hydro-dynamic behavior, can differently affect the total thermal transmittance of the entire structure. This paper aims to provide an experimental analysis of the total U-value of a ventilated wall assembly measured in a building prototype following the average and dynamic methods defined by ISO 9869-1. Differences between the calculated theoretical U-value and the measured U-value are compared. The contribution of the thermal resistance of the ventilated air-space in the total thermal transmittance of the wall assembly is also analyzed. The results show that the air movement and the enthalpy change in the ventilated cavity can affect the thermal performance of the wall structure to a certain extent.

Analysis of Building Envelope Performance Effects of an Insulating Semi-Transparent Photovoltaic (STPV) Glazing Unit

2014 ◽  
Author(s):  
Dirk V. P. McLaughlin ◽  
Konstantinos Kapsis ◽  
Andreas K. Athienitis ◽  
Sam Siassi ◽  
Livio Nichilo
Keyword(s):  
Performance Standards ◽  
Energy Performance ◽  
Building Envelope ◽  
Commercial Building ◽  
Heating And Cooling ◽  
Performance Effects ◽  
Gas Consumption ◽  
U Value ◽  
And Performance ◽  
Cooling Loads

This paper presents characterization results for the electrical and thermal properties of a unique insulating semi-transparent photovoltaic (STPV) glazing unit using calorimetry hot box methods finding a U-value of 1.09 W/m2·°C and a SHGC of 0.11. These properties are then applied to an energy model of a case study commercial building in a continental climate region to examine the effects of utilizing STPV in the building envelope on the electricity and natural gas consumption levels and peak demands. The results indicate that such a building envelope can significantly reduce heating and cooling loads compared to standard glazing which would help architects maintain the desirable properties of highly glazed façades while avoiding the drop in building energy performance that could make adhering to increasingly stringent building codes and performance standards difficult. The paper also presents simulation results for the photovoltaic energy generation of the vertical STPV façades at two building orientations.

Impact of roof shading on building energy performance in warm & humid climatic places of India

2020 ◽  
pp. 50-64
Author(s):  
Kuladeep Kumar Sadevi ◽  
Avlokita Agrawal
Keyword(s):  
Energy Consumption ◽  
Energy Conservation ◽  
Energy Performance ◽  
General Assumption ◽  
Climatic Conditions ◽  
Building Envelope ◽  
Passive Cooling ◽  
Base Case ◽  
U Value ◽  
The Impact

With the rise in awareness of energy efficient buildings and adoption of mandatory energy conservation codes across the globe, significant change is being observed in the way the buildings are designed. With the launch of Energy Conservation Building Code (ECBC) in India, climate responsive designs and passive cooling techniques are being explored increasingly in building designs. Of all the building envelope components, roof surface has been identified as the most significant with respect to the heat gain due to the incident solar radiation on buildings, especially in tropical climatic conditions. Since ECBC specifies stringent U-Values for roof assembly, use of insulating materials is becoming popular. Along with insulation, the shading of the roof is also observed to be an important strategy for improving thermal performance of the building, especially in Warm and humid climatic conditions. This study intends to assess the impact of roof shading on building’s energy performance in comparison to that of exposed roof with insulation. A typical office building with specific geometry and schedules has been identified as base case model for this study. This building is simulated using energy modelling software ‘Design Builder’ with base case parameters as prescribed in ECBC. Further, the same building has been simulated parametrically adjusting the amount of roof insulation and roof shading simultaneously. The overall energy consumption and the envelope performance of the top floor are extracted for analysis. The results indicate that the roof shading is an effective passive cooling strategy for both naturally ventilated and air conditioned buildings in Warm and humid climates of India. It is also observed that a fully shaded roof outperforms the insulated roof as per ECBC prescription. Provision of shading over roof reduces the annual energy consumption of building in case of both insulated and uninsulated roofs. However, the impact is higher for uninsulated roofs (U-Value of 3.933 W/m2K), being 4.18% as compared to 0.59% for insulated roofs (U-Value of 0.33 W/m2K).While the general assumption is that roof insulation helps in reducing the energy consumption in tropical buildings, it is observed to be the other way when insulation is provided with roof shading. It is due to restricted heat loss during night.

scholarly journals A Fundamental Study on the Development of New Energy Performance Index in Office Buildings

Energies ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2064
Author(s):  
Jin-Hee Kim ◽  
Seong-Koo Son ◽  
Gyeong-Seok Choi ◽  
Young-Tag Kim ◽  
Sung-Bum Kim ◽  
...  
Keyword(s):  
Energy Consumption ◽  
Energy Requirement ◽  
Energy Performance ◽  
Office Buildings ◽  
Light Transmittance ◽  
Wall Structure ◽  
Fundamental Study ◽  
Future Studies ◽  
U Value ◽  
The Impact

Recently, there have been significant concerns regarding excessive energy use in office buildings with a large window-to-wall ratio (WWR) because of the curtain wall structure. However, prior research has confirmed that the impact of the window area on energy consumption varies depending on building size. A newly proposed window-to-floor ratio (WFR) correlates better with energy consumption in the building. In this paper, we derived the correlation by analyzing a simulation using EnergyPlus, and the results are as follows. In the case of small buildings, the results of this study showed that the WWR and energy requirement increase proportionally, and the smaller the size is, the higher the energy sensitivity will be. However, results also confirmed that this correlation was not established for buildings approximately 3600 m2 or larger. Nevertheless, from analyzing the correlation between the WFR and the energy requirements, it could be deduced that energy required increased proportionally when the WFR was 0.1 or higher. On the other hand, the correlation between WWR, U-value, solar heat gain coefficient (SHGC), and material property values of windows had little effect on energy when the WWR was 20%, and the highest effect was seen at a WWR of 100%. Further, with an SHGC below 0.3, the energy requirement decreased with an increasing WWR, regardless of U-value. In addition, we confirmed the need for in-depth research on the impact of the windows’ U-value, SHGC, and WWR, and this will be verified through future studies. In future studies on window performance, U-value, SHGC, visible light transmittance (VLT), wall U-value as sensitivity variables, and correlation between WFR and building size will be examined.

scholarly journals Circularity concepts for offsite prefabricated energy renovation of apartment buildings

2021 ◽  
Vol 2069 (1) ◽  
pp. 012074
Author(s):  
Kalle Kuusk ◽  
Kristel Kullerkupp ◽  
Peep Pihelo ◽  
Michiel Ritzen ◽  
Ana Tisov ◽  
...  
Keyword(s):  
Window Glass ◽  
Energy Performance ◽  
Building Envelope ◽  
Full Potential ◽  
Careful Selection ◽  
Thermal Transmittance ◽  
Building Component ◽  
Materials Used ◽  
Good Possibility ◽  
Selection Of

Abstract Deep energy renovation includes the realisation of the full potential of energy performance. A circular deep renovation, which contributes to a circular built environment, is based on 100% life cycle renewable energy, and all materials used within the system boundaries are part of infinite technical or biological cycles with the lowest quality loss as possible. In the current study, the circularity potential was assessed for deep energy renovation from different aspects: circularity of materials, building component and building structure. Careful selection of materials as well as connection, position and disassembly possibilities are needed to increase the degree of circularity. This shows a good possibility to increase energy performance by using circularity principles. The window glass circularity analyse showed that, at best, the thermal transmittance of a new circular product can be more than three times lower than the original. The circular use of materials, components, and structures pose new challenges for the building physic design of building envelope structures.

scholarly journals Special Issue “Building Thermal Envelope”

Energies ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1061 ◽  
Author(s):  
Jorge de Brito ◽  
M. Glória Gomes
Keyword(s):  
Performance Standards ◽  
Energy Performance ◽  
Building Envelope ◽  
Special Issue ◽  
Zero Energy ◽  
Indoor Comfort ◽  
Zero Energy Buildings

The increasing requirements in building thermal and energy performance standards and the need to design nearly zero-energy buildings, while still enhancing the indoor comfort conditions, have led to a demand for more efficient thermal building envelope solutions [...]

scholarly journals New Equation for Optimal Insulation Dependency on the Climate for Office Buildings

Energies ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 321
Author(s):  
Kaiser Ahmed ◽  
Jarek Kurnitski
Keyword(s):  
Energy Performance ◽  
Building Envelope ◽  
Cold Climate ◽  
Office Buildings ◽  
Sensitivity Analyses ◽  
Base Temperature ◽  
Optimal Solutions ◽  
U Value ◽  
New Equation ◽  
Different Climates

The comparison of building energy efficiency in different climates is a growing issue. Unique structural solutions will not ensure the same energy use, but the differences also remain if cost-optimal solutions are applied. This study developed a new equation for the assessment of building envelope optimal insulation in different climates for office buildings. The developed method suggests determining actual degree days from simulated heating energy need and the thermal conductance of a building, avoiding in such a way the use of a base temperature. The method was tested in four climates and validated against cost-optimal solutions solved with optimization. The accuracy of the method was assessed with sensitivity analyses of key parameters such as window-to-wall ratios (WWRs), window g-values, costs of heating, and electricity. These results showed that the existing square root equation overestimated the climate difference effect so that the calculation from the cold climate U-value resulted in less insulation than cost-optimal in warmer climates. Parametric analyses revealed that the power value of 0.2 remarkably improved the accuracy as well as performance worked well in all cases and can be recommended as a default value. Sensitivity analyses with a broad range of energy costs and window parameters revealed that the developed equation resulted in maximum 5% underestimation and maximum 7% overestimation of an average area-weighted optimal U-value of building envelope in another climate. The developed method allows objectively to compare optimal insulation of the building envelope in different climates. The method is easy to apply for energy performance comparison of similar buildings in different climates and also for energy performance requirements comparison.

scholarly journals Analytical Methods to Estimate the Thermal Transmittance of LSF Walls: Calculation Procedures Review and Accuracy Comparison

Energies ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 840 ◽  
Author(s):  
Paulo Santos ◽  
Gabriela Lemes ◽  
Diogo Mateus
Keyword(s):  
Numerical Simulations ◽  
Analytical Methods ◽  
Numerical Models ◽  
Building Envelope ◽  
Zone Method ◽  
Thermal Transmittance ◽  
Accuracy Comparison ◽  
Reliable Assessment ◽  
U Value ◽  
Calculation Procedures

An accurate evaluation of the thermal transmittance ( U -value) of building envelope elements is fundamental for a reliable assessment of their thermal behaviour and energy efficiency. Simplified analytical methods to estimate the U -value of building elements could be very useful to designers. However, the analytical methods applied to lightweight steel framed (LSF) elements have some specific features, being more challenging to use and to obtain a reliable accurate U -value with. In this work, the main analytical methods available in the literature were identified, the calculation procedures were reviewed and their accuracy was evaluated and compared. With this goal, six analytical methods were used to estimate the U -values of 80 different LSF wall models. The obtained analytical U -values were compared with those provided by numerical simulations, which were used as reference U -values. The numerical simulations were performed using a 2D steady-state finite element method (FEM)-based software, THERM. The reliability of these numerical models was ensured by comparison with benchmark values and by an experimental validation. All the evaluated analytical methods showed a quite good accuracy performance, the worst accuracy being found in cold frame walls. The best and worst precisions were found in the Modified Zone Method and in the Gorgolewski Method 2, respectively. Very surprisingly, the ISO 6946 Combined Method showed a better average precision than other two methods, which were specifically developed for LSF elements.

scholarly journals Investigation of the envelope’s thermal transmittance influence on the energy efficiency of residential buildings under various Mediterranean region climates

2021 ◽  
Vol 899 (1) ◽  
pp. 012009
Author(s):  
A C Karanafti ◽  
T G Theodosiou
Keyword(s):  
Energy Efficiency ◽  
Residential Buildings ◽  
Residential Building ◽  
Energy Performance ◽  
Building Envelope ◽  
Ambient Conditions ◽  
Cooling Period ◽  
Thermal Transmittance ◽  
System A ◽  
Mediterranean Regions

Abstract Improving the energy efficiency of residential buildings is of outmost importance for reducing their environmental footprint. Recent studies demonstrate that a highly insulated building envelope may burden the building’s performance during the cooling period, especially in regions with hot summers. In this study, the energy performance of a residential building in different Mediterranean regions (Jordan, Greece, Iraq, Egypt, Syria, Morocco, Cyprus, Saudi Arabia, Libya, and Spain) is investigated. Two thermal transmittance values are applied to the building shell, a scenario with a very low one and a scenario with a higher one, to examine under which conditions the cooling performance is improved. A dynamic insulation configuration is also implemented, and its operation is studied for the cooling period of each city. It is concluded that in Southern European and Northern African regions building envelopes with lower thermal resistances perform better, while in even Southern regions an increased thermal resistance may prevent the heat from entering the building more effectively. With the switching insulation system, a great reduction in the cooling demands was reported, which reached up to 50% in Spain, and it was shown that in the southern regions the configuration’s operation should be customized to the ambient conditions to optimize its performance.

scholarly journals Residential Energy Efficiency: Benefits of Minimum Energy Performance Standard (MEPS) Implementation for Television in Malaysia

2018 ◽  
Vol 7 (4.35) ◽  
pp. 835
Author(s):  
Aishah Mohd Isa ◽  
Mohd Eqwan Mohd Roslan ◽  
Siti Fatihah Salleh
Keyword(s):  
Energy Efficiency ◽  
Performance Test ◽  
Minimum Energy ◽  
National Level ◽  
Performance Standards ◽  
Energy Performance ◽  
Performance Standard ◽  
Residential Energy ◽  
Air Conditioners ◽  
Residential Energy Efficiency

A popular strategy for promoting energy efficiency at the national level is through the minimum energy performance standards (MEPS). Malaysia implemented MEPS in 2013 for five common household appliances; air conditioners, refrigerators, fans, televisions, and lamps. These products must undergo a performance test. Only products that meet the minimum standards are allowed to enter the Malaysian market. Based on their performance, ratings are awarded ranging from 2-star up to 5-star. A survey the authors conducted in 2017 found that about 98% of televisions sold in Malaysia have already achieved 5-star rating. This paper explores the implications of this finding and quantifies the possible savings that can be achieved in terms of electricity savings and emission reductions. 

scholarly journals Thermal Transmittance of Internal Partition and External Facade LSF Walls: A Parametric Study

Energies ◽  
2019 ◽  
Vol 12 (14) ◽  
pp. 2671 ◽  
Author(s):  
Santos ◽  
Lemes ◽  
Mateus
Keyword(s):  
Composite System ◽  
Expanded Polystyrene ◽  
Wall Structure ◽  
Reference Case ◽  
Partition Wall ◽  
Thermal Transmittance ◽  
Steel Material ◽  
Internal Partition ◽  
U Value ◽  
Reduce Energy Consumption

Light steel framed (LSF) construction is becoming widespread as a quick, clean and flexible construction system. However, these LSF elements need to be well designed and protected against undesired thermal bridges caused by the steel high thermal conductivity. To reduce energy consumption in buildings it is necessary to understand how heat transfer happens in all kinds of walls and their configurations, and to adequately reduce the heat loss through them by decreasing its thermal transmittance (U-value). In this work, numerical simulations are performed to assess different setups for two kinds of LSF walls: an interior partition wall and an exterior facade wall. Several parameters were evaluated separately to measure their influence on the wall U-value, and the addition of other elements was tested (e.g., thermal break strips) with the aim of achieving better thermal performances. The simulation modeling of a LSF interior partition with thermal break strips indicated a 24% U-value reduction in comparison with the reference case of using the LSF alone (U = 0.449 W/(m2.K)). However, when the clearance between the steel studs was simulated with only 300 mm there was a 29% increase, due to the increase of steel material within the wall structure. For exterior facade walls (U = 0.276 W/(m2.K)), the model with 80 mm of expanded polystyrene (EPS) in the exterior thermal insulation composite system (ETICS) reduced the thermal transmittance by 19%. Moreover, when the EPS was removed the U-value increased by 79%.

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