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See detailPost-occupancy evaluation of residential buildings in Luxembourgwith centralized and decentralized ventilation systems, focusing onindoor air quality (IAQ). Assessment by questionnaires and physicalmeasurements
Ferreira Silva, Marielle; Maas, Stefan UL; Artur de Souza, Henor et al

in Energy and Buildings (2017), 148

tComplete knowledge about habits of the occupants, including their opinions regarding ventilation sys-tems is an important condition for reducing the consumption of natural resources and improving ... [more ▼]

tComplete knowledge about habits of the occupants, including their opinions regarding ventilation sys-tems is an important condition for reducing the consumption of natural resources and improving indoorcomfort. In addition, uncomforted occupants tend to take measures to improve their situation, whichmay increase energy consumption. Advanced thermal models for buildings can perhaps predict interac-tions between the IAQ determinants, e.g. energy consumption, ventilation and comfort, but do not takeinto account the behavior of residents. By questionnaires and physical measurements this study evalu-ated dwellings equipped partly with centralized and partly with decentralized ventilation systems withheat recovery. This field study involved two post-occupied residential buildings situated in the city ofEsch-sur-Alzette, Luxembourg, during spring season 2015. Thus, both the physical measurements andquestionnaires were considered. The results obtained demonstrated that more than 80% of the residentswere satisfied and the perceived IAQ was judged “normal”, “good” or even “very good”. Furthermore,the measurements performed detected in some cases malfunction of ventilation devices, wherefore theoccupants were unable. [less ▲]

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See detailField tests of centralized and decentralized ventilation units inresidential buildings – Specific fan power, heat recovery efficiency,shortcuts and volume flow unbalances
Merzkirch, Alexander UL; Maas, Stefan UL; Scholzen, Frank UL et al

in Energy and Buildings (2016), 116(2016), 376-383

tThe energy efficient operation of mechanical ventilation systems depends on various parameters. InLuxembourg, field tests with 20 centralized and 60 decentralized mechanical ventilation systems insingle ... [more ▼]

tThe energy efficient operation of mechanical ventilation systems depends on various parameters. InLuxembourg, field tests with 20 centralized and 60 decentralized mechanical ventilation systems insingle- and multi-family homes were conducted in order to measure the actual performance of thosesystems in occupied buildings. The considered parameters were: Main air flows, internal and externalrecirculation, sensitivity to differential pressure, specific fan power and heat recovery efficiency. In manycases, the performance of the ventilation units was lower than expected. The systems showed deviationsbetween supply and exhaust flows of up to 60%. In particular, the air flow in decentralized units wasstrongly influenced by pressure differences between the inside and outside due to wind or stack effectswhich leads to a decreased heat recovery efficiency. The total mean recirculation ratio was 6.5%, with astandard deviation of 12.5% for centralized and 13 ± 6.2% for decentralized devices. As a consequence,the delivered flow of fresh air is smaller by the amount of recirculation. The specific fan power, theratio between air flow and power consumption, was measured with 0.475 ± 0.37 Wh/m3for centralizedand 0.22 ± 0.023 Wh/m3for decentralized systems. The lower value for the decentralized systems canbe explained by lower pressure losses due to the lack of ductwork. The heat recovery efficiency was0.65 ± 0.24 for centralized systems and 0.7 ± 0.17 for decentralized systems which is significantly lowerthan nominal values provided by the manufacturers. The results of this study show that the overall energyefficiency of ventilation devices installed in residential buildings under real working conditions are oftenlower than expected. These findings could possibly serve as indicators for future research & developmentat manufacturer and commissioning level. [less ▲]

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See detailEnergy consumption of non-retrofitted institutional building stock inLuxembourg and the potential for a cost-efficient retrofit
Hoos, Thorsten UL; Merzkirch, Alexander UL; Maas, Stefan UL et al

in Energy and Buildings (2016), 123(2016), 162-168

The public building stock of a country, consisting of schools, offices, accommodation facilities, single-and multi-family homes, accounts for a high consumption of electrical and heat energy. Therefore ... [more ▼]

The public building stock of a country, consisting of schools, offices, accommodation facilities, single-and multi-family homes, accounts for a high consumption of electrical and heat energy. Therefore, thisstock is often subject to actions with the goal of lowering this energy usage by increasing the efficiencyof those buildings. This is usually done by applying measures to the building envelope like insulationand/or new windows and by using a more efficient HVAC technology. But often, in the initial state, thecurrent energy consumption of such a stock is unknown or only known for single buildings. In this case,the calculation of energy and cost savings is either impossible or not exact. This paper shows a way toquantify and categorize the end-energy for heat use of the public building stock in Luxembourg, whichconsists of a gross area of 1.744 million m2. This analysis was carried out in cooperation with the nationaladministration of public buildings.A certain amount of sample buildings was analyzed and then separated into three groups of low,normal and high end-energy use. The boundaries of these groups were chosen according to literaturevalues, derived from European retrofit projects, which also served as the source for possible renovationcosts. This data was extrapolated to the whole stock. This information serves as a basis for future decisionsconcerning the retrofit of those buildings and makes a calculation of costs possible.As a result, the type of buildings with the highest potential for retrofit measures was identified. Schools,offices and accommodation facilities with a “high” consumption of more than 190 kWh/(m2a) show thehighest economic potential with retrofit costs of 0.04–0.08 D /kWh if their energy consumption is loweredto values of around 90–100 kWh. Other groups of buildings show higher costs of around 0.07–0.19 D /kWh. [less ▲]

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