Assessing the potential of ventilated façades on reducing a buildings’ thermal load using decoupled COMSOL simulations

Solar radiation is a prominent contributor of energy in buildings, and can be transmitted directly into a building through opaque surfaces, but it can also be absorbed by building components (i.e. walls, roofs etc.). Both cause heat addition to the building interior. The application of ventilated facades can help reduce thermal loads during high temperatures and solar radiation, which in effect reduces the energy consumption due to air-conditioning systems. This is a passive cooling technique that could be developed to a greater extent in order to improve indoor climatic conditions and the microclimate around buildings. This study discusses the use and effect of ventilated facades, with an external facade cladding, a sub-structure anchored to the wall surface of the building under solar radiation, while designing facade elements numerically using COMSOL, to create the highest achievable velocity inside the air cavity. The mass air flow inside the cavity, due to buoyancy effects (natural convection) and wind (forced convection), can carry away heat load passively. Results show that energy saving is increased with a ventilated facade over a conventional facade, and is more effective for higher solar radiation and higher air velocity inside the cavity. In the second part of the study it becomes clear that facade elements can be designed in such a way that they increase the air velocity inside the cavity to remove more heat efficiently. An improvement of up to 75% of the air velocity is reached in some parts of the cavity for the implemented design in comparison to the reference case

Ondergronds als alternatief voor bovengronds bouwen

Ondergrondse gebouwen worden gezien als alternatief voor bovengrondse gebouwen, omdat het totale energiegebruik ervan lager ligt. Verschillende aspecten bepalen het energiegebruik door warmte- en koudevraag van deze gebouwen, zoals de gebouwfunctie, gebouwmaterialen, gebouwgrootte en -vorm en het klimaat. Slechts enkele onderzoeken naar warmteoverdracht in ondergrondse gebouwen richten zich op het energiegebruik ten opzichte van bovengrondse gebouwen. Onderzoek naar de relatie tussen het energiegebruik en de verschillende ontwerpaspecten in verschillende klimaten bestaat er niet. Het in dit artikel beschreven onderzoek [1] bevat een vergelijkende analyse van het berekende jaarlijkse energiegebruik van bovengrondse en ondergrondse gebouwen, gericht op de evaluatie van de potentie in energiebesparing door het gebruik van ondergrondse gebouwen

Quantifying the Underlying Causes of a Discrepancy Between Predicted and Measured Energy Use

Simulation is commonly utilized as a best practice approach to assess building performance in the building industry. However, the built environment is complex and influenced by a large number of independent and interdependent variables, making it difficult to achieve an accurate representation of real-world building energy in-use. This gives rise to significant discrepancies between simulation results and actual measured energy consumption, termed “the performance gap.” The research presented in this paper quantified the impact of underlying causes of this gap, by developing building simulation models of four existing non-domestic buildings, and then calibrating them toward their measured energy use at a high level of data granularity. It was found that discrepancies were primarily related to night-time use and seasonality in universities is not being captured correctly, in addition to equipment and server power density being underestimated (indirectly impacting heating and cooling loads). Less impactful parameters were among others; material properties, system efficiencies, and air infiltration assumptions

THE IMPACT OF DIETARY PROTEIN OR AMINO ACID SUPPLEMENTATION ON MUSCLE MASS AND STRENGTH IN ELDERLY PEOPLE: INDIVIDUAL PARTICIPANT DATA AND META-ANALYSIS OF RCT’S

Objectives Increasing protein or amino acid intake has been promoted as a promising strategy to increase muscle mass and strength in elderly people, however, long-term intervention studies show inconsistent findings. Therefore, we aim to determine the impact of protein or amino acid supplementation compared to placebo on muscle mass and strength in older adults by combining the results from published trials in a metaanalysis and pooled individual participant data analysis. Design We searched Medline and Cochrane databases and performed a meta-analysis on eight available trials on the effect of protein or amino acid supplementation on muscle mass and strength in older adults. Furthermore, we pooled individual data of six of these randomized double-blind placebo-controlled trials. The main outcomes were change in lean body mass and change in muscle strength for both the meta-analysis and the pooled analysis. Results The meta-analysis of eight studies (n=557) showed no significant positive effects of protein or amino acid supplementation on lean body mass (mean difference: 0.014 kg: 95% CI -0.152; 0.18), leg press strength (mean difference: 2.26 kg: 95% CI -0.56; 5.08), leg extension strength (mean difference: 0.75 kg: 95% CI: -1.96, 3.47) or handgrip strength (mean difference: -0.002 kg: 95% CI -0.182; 0.179). Likewise, the pooled analysis showed no significant difference between protein and placebo treatment on lean body mass (n=412: p=0.78), leg press strength (n=121: p=0.50), leg extension strength (n=121: p=0.16) and handgrip strength (n=318: p=0.37). Conclusions There is currently no evidence to suggest that protein or amino acid supplementation without concomitant nutritional or exercise interventions increases muscle mass or strength in predominantly healthy elderly people

Heating and cooling energy demand in underground buildings: Potential for saving in various climates and functions

Underground buildings are pointed out as alternatives to conventional aboveground buildings for reducing total energy requirements, while alleviating land use and location problems. This paper investigates the potential in reducing the heating and cooling energy demand of underground buildings compared to aboveground buildings. Monthly calculations based on EN-ISO 13790 are performed to obtain the annual heating and cooling energy demand of aboveground and underground buildings for various climates, building functions and underground depths. Uncertainty of input parameters is considered in the calculation, and sensitivity analysis is carried out. Energy reduction is achievable for all climates and functions when underground and aboveground buildings, but the magnitude is related to the combination of different design elements. Results show that 11% of cases analysed can be considered near zero-energy buildings (annual energy demand less than 10 kWh/m2y). Sensitivity analysis indicates that the most influential parameters depend on the climate and building function. As expected, building functions with high internal gains perform better in cold climates, and the ones with low internal gains perform better in hot climates

Assessing the potential of ventilated façades on reducing a buildings’ thermal load using decoupled COMSOL simulations

Solar radiation is a prominent contributor of energy in buildings, and can be transmitted directly into a building through opaque surfaces, but it can also be absorbed by building components (i.e. walls, roofs etc.). Both cause heat addition to the building interior. The application of ventilated facades can help reduce thermal loads during high temperatures and solar radiation, which in effect reduces the energy consumption due to air-conditioning systems. This is a passive cooling technique that could be developed to a greater extent in order to improve indoor climatic conditions and the microclimate around buildings. This study discusses the use and effect of ventilated facades, with an external facade cladding, a sub-structure anchored to the wall surface of the building under solar radiation, while designing facade elements numerically using COMSOL, to create the highest achievable velocity inside the air cavity. The mass air flow inside the cavity, due to buoyancy effects (natural convection) and wind (forced convection), can carry away heat load passively. Results show that energy saving is increased with a ventilated facade over a conventional facade, and is more effective for higher solar radiation and higher air velocity inside the cavity. In the second part of the study it becomes clear that facade elements can be designed in such a way that they increase the air velocity inside the cavity to remove more heat efficiently. An improvement of up to 75% of the air velocity is reached in some parts of the cavity for the implemented design in comparison to the reference case