Iro Livada - Academia.edu (original) (raw)
Papers by Iro Livada
A Handbook of Sustainable Building Design and Engineering, 2018
Climate, 2021
Recent climatic trends of two nearby stations in Sydney were examined in terms of hourly ambient ... more Recent climatic trends of two nearby stations in Sydney were examined in terms of hourly ambient air temperature and wind direction for the time period 1999–2019. A reference was set for the monthly number of cooling (CDH) and heating (HDH) degree hours and the number of monthly hours that temperatures exceeded 24 °C (T24) or were below 14 °C (T14), parameters affecting not only the energy demands but also the quality of life. The degree hours were linked to the dominant synoptic conditions and the local phenomena: sea breeze and inland winds. The results indicated that both areas had higher mean monthly number of HDH (980–1421) than CDH (397–748), thus higher heating demands. The results also showed a higher mean monthly number of T14 (34–471) than T24 (40–320). A complete spatiotemporal profile of the climatic variations was given through the analysis of their dynamic progress and correlation. In order to estimate the daily values of CDH and HDH, T24 and T14 empirical models were ...
Climate, 2019
High daily temperatures in the Mediterranean and Europe have been documented in observation and m... more High daily temperatures in the Mediterranean and Europe have been documented in observation and modeling studies. Long-term temperature data, from 1988 to 2017, from a suburban station and an urban station in Nicosia, Cyprus have been analyzed, and the diurnal temperature range (DTR) trend was investigated. The seasonal Mann–Kendall test revealed a decreasing DTR trend of −0.24 °C/decade at the urban station and −0.36 °C/decade at the suburban station, which were attributed to an increase in the daily minimum temperature. Variations in precipitation, longwave radiation, ultraviolet-A (UVA), ultraviolet-B (UVB), cloud cover, water vapor, and urbanization were used to assess their possible relationship with regional DTR. The clustering of daytime and night-time data showed a strong relationship between the DTR and observed cloud cover, net longwave radiation, and precipitation. Clouds associated with smaller shortwave and net longwave radiation reduce the DTR by decreasing the surface...
Energy and Buildings, 2005
A number of field and indoor experimental procedures were performed in three typical apartment bu... more A number of field and indoor experimental procedures were performed in three typical apartment buildings located in two street canyons characterized by different urban features, during summer period 2002 in Athens. Natural, mechanical and hybrid ventilation measurements were performed based on the tracer gas method on a circular basis within the 24-h period. The indoor exchange rates are estimated using both single and multi-zone approaches based on the mass balance of two tracer gases (N 2 O and SF 6). The experiments pointed out that, in spite of the canyon effect, appreciable ventilation rates can be obtained with natural ventilation, especially when cross ventilation with two or more windows is measured. In the presence of cross ventilation and with sufficient ambient wind speeds, natural ventilation is shown to be more effective, with regard to ACH, in comparison with hybrid. However, when only single-sided ventilation is possible or under calm conditions hybrid ventilation has a slight advantage over natural. A comparative analysis is made for the total air change rates estimated with the single and multi-zone methodologies. The multi-zone approach, in spite of its better theoretical basis, has been found more sensitive to the accuracy of the measured concentrations, especially when a single tracer is used.
Building and Environment, 2008
An experimental investigation of the performance of natural, mechanical and hybrid ventilation sy... more An experimental investigation of the performance of natural, mechanical and hybrid ventilation systems was carried out in an urban measurement campaign during summer period 2002 in Athens, Greece. Three building apartments characterized by different geometry and located in two street canyons with different orientation were studied. The aim was to show the impact of the urban environment on the ventilation efficiency of natural and hybrid systems. The tracer gas decay method has been applied during the experimental procedures with one (N 2 O) and two tracer gases (N 2 O and SF 6). Based on the results of air-exchange rates using multizone methods from a previous study, a further analysis is performed in the present work for the evaluation of the performance of different ventilation systems in urban conditions, with emphasis on the ventilation efficiency. A methodology to estimate the air-exchange efficiency, on the basis of room mean age of air, in multitracer gas experiments is introduced. In spite of the reduced wind speeds due to the canyon effect, appreciable ventilation rates can be obtained with natural ventilation, especially when cross-ventilation with two or more windows is measured. For single-sided ventilation or under calm conditions, hybrid ventilation has only a slight advantage over natural, either in terms of air-exchange rates or of air-exchange efficiencies.
Building and Environment, 2008
This paper describes the measurements and analysis of an experimental campaign performed in an ur... more This paper describes the measurements and analysis of an experimental campaign performed in an urban street canyon in Athens, Greece. A number of field and indoor experimental procedures were organized during summer 2002 aiming at the investigation of the impact of urban environment on the potential of natural and hybrid ventilation. The present study is focused on the experimental investigation of thermal characteristics of a typical street canyon, oriented in ESE-WNW direction, under hot weather conditions. The temporal and spatial distribution of air and surface temperatures is examined. Emphasis was given on the vertical distribution of air and surface temperatures and the air temperature profile in the centre of canyon under different weather conditions. The measured surface temperature differences across the street reached almost 30 1C and this favored the overheating of lower air levels. Buoyancy generated mainly from asphalt-street heating resulted in the development of the predominant recirculation inside the street canyon.
Building and Environment, 2008
Regular air tightness and infiltration measurements were performed in forty houses, in the area o... more Regular air tightness and infiltration measurements were performed in forty houses, in the area of Attica, Greece. Two measurement methods were used, the tracer gas decay method and the Blower Door tests method. Blower Door measurements were done in accordance with EN ISO 13829 [1]. Ambient conditions and temperature fluctuations inside the houses were measured as well. A classification of houses examined, based on experiments' results was acted out in accordance with EN ISO 13790 [2]. The houses were classified into three air tightness categories, in regard to their air tightness in natural conditions and at a pressure difference of 50 Pa. Furthermore, the total frame length was estimated for the whole housing stock, and a correlation between the air tightness measurements at a pressure difference of 50Pa and the total frame length was examined, for the sample of buildings and for each air tightness category. A correlation between the airflow values, as they resulted from the fan pressurization method and the average infiltration rates, calculated by the tracer gas experiment results, has been extracted. Moreover, the effect of climate data including temperature and windiness and construction quality on the houses' infiltration characteristics has been investigated.
Science of The Total Environment, 2019
Persistence is observed between consecutive months and days for mean Tair. • An increasing tenden... more Persistence is observed between consecutive months and days for mean Tair. • An increasing tendency is observed for Tair and degree days for most months. • In winter, degree days show a decreasing trend indicating lower needs for heating.
A Handbook of Sustainable Building Design and Engineering, 2018
Climate, 2021
Recent climatic trends of two nearby stations in Sydney were examined in terms of hourly ambient ... more Recent climatic trends of two nearby stations in Sydney were examined in terms of hourly ambient air temperature and wind direction for the time period 1999–2019. A reference was set for the monthly number of cooling (CDH) and heating (HDH) degree hours and the number of monthly hours that temperatures exceeded 24 °C (T24) or were below 14 °C (T14), parameters affecting not only the energy demands but also the quality of life. The degree hours were linked to the dominant synoptic conditions and the local phenomena: sea breeze and inland winds. The results indicated that both areas had higher mean monthly number of HDH (980–1421) than CDH (397–748), thus higher heating demands. The results also showed a higher mean monthly number of T14 (34–471) than T24 (40–320). A complete spatiotemporal profile of the climatic variations was given through the analysis of their dynamic progress and correlation. In order to estimate the daily values of CDH and HDH, T24 and T14 empirical models were ...
Climate, 2019
High daily temperatures in the Mediterranean and Europe have been documented in observation and m... more High daily temperatures in the Mediterranean and Europe have been documented in observation and modeling studies. Long-term temperature data, from 1988 to 2017, from a suburban station and an urban station in Nicosia, Cyprus have been analyzed, and the diurnal temperature range (DTR) trend was investigated. The seasonal Mann–Kendall test revealed a decreasing DTR trend of −0.24 °C/decade at the urban station and −0.36 °C/decade at the suburban station, which were attributed to an increase in the daily minimum temperature. Variations in precipitation, longwave radiation, ultraviolet-A (UVA), ultraviolet-B (UVB), cloud cover, water vapor, and urbanization were used to assess their possible relationship with regional DTR. The clustering of daytime and night-time data showed a strong relationship between the DTR and observed cloud cover, net longwave radiation, and precipitation. Clouds associated with smaller shortwave and net longwave radiation reduce the DTR by decreasing the surface...
Energy and Buildings, 2005
A number of field and indoor experimental procedures were performed in three typical apartment bu... more A number of field and indoor experimental procedures were performed in three typical apartment buildings located in two street canyons characterized by different urban features, during summer period 2002 in Athens. Natural, mechanical and hybrid ventilation measurements were performed based on the tracer gas method on a circular basis within the 24-h period. The indoor exchange rates are estimated using both single and multi-zone approaches based on the mass balance of two tracer gases (N 2 O and SF 6). The experiments pointed out that, in spite of the canyon effect, appreciable ventilation rates can be obtained with natural ventilation, especially when cross ventilation with two or more windows is measured. In the presence of cross ventilation and with sufficient ambient wind speeds, natural ventilation is shown to be more effective, with regard to ACH, in comparison with hybrid. However, when only single-sided ventilation is possible or under calm conditions hybrid ventilation has a slight advantage over natural. A comparative analysis is made for the total air change rates estimated with the single and multi-zone methodologies. The multi-zone approach, in spite of its better theoretical basis, has been found more sensitive to the accuracy of the measured concentrations, especially when a single tracer is used.
Building and Environment, 2008
An experimental investigation of the performance of natural, mechanical and hybrid ventilation sy... more An experimental investigation of the performance of natural, mechanical and hybrid ventilation systems was carried out in an urban measurement campaign during summer period 2002 in Athens, Greece. Three building apartments characterized by different geometry and located in two street canyons with different orientation were studied. The aim was to show the impact of the urban environment on the ventilation efficiency of natural and hybrid systems. The tracer gas decay method has been applied during the experimental procedures with one (N 2 O) and two tracer gases (N 2 O and SF 6). Based on the results of air-exchange rates using multizone methods from a previous study, a further analysis is performed in the present work for the evaluation of the performance of different ventilation systems in urban conditions, with emphasis on the ventilation efficiency. A methodology to estimate the air-exchange efficiency, on the basis of room mean age of air, in multitracer gas experiments is introduced. In spite of the reduced wind speeds due to the canyon effect, appreciable ventilation rates can be obtained with natural ventilation, especially when cross-ventilation with two or more windows is measured. For single-sided ventilation or under calm conditions, hybrid ventilation has only a slight advantage over natural, either in terms of air-exchange rates or of air-exchange efficiencies.
Building and Environment, 2008
This paper describes the measurements and analysis of an experimental campaign performed in an ur... more This paper describes the measurements and analysis of an experimental campaign performed in an urban street canyon in Athens, Greece. A number of field and indoor experimental procedures were organized during summer 2002 aiming at the investigation of the impact of urban environment on the potential of natural and hybrid ventilation. The present study is focused on the experimental investigation of thermal characteristics of a typical street canyon, oriented in ESE-WNW direction, under hot weather conditions. The temporal and spatial distribution of air and surface temperatures is examined. Emphasis was given on the vertical distribution of air and surface temperatures and the air temperature profile in the centre of canyon under different weather conditions. The measured surface temperature differences across the street reached almost 30 1C and this favored the overheating of lower air levels. Buoyancy generated mainly from asphalt-street heating resulted in the development of the predominant recirculation inside the street canyon.
Building and Environment, 2008
Regular air tightness and infiltration measurements were performed in forty houses, in the area o... more Regular air tightness and infiltration measurements were performed in forty houses, in the area of Attica, Greece. Two measurement methods were used, the tracer gas decay method and the Blower Door tests method. Blower Door measurements were done in accordance with EN ISO 13829 [1]. Ambient conditions and temperature fluctuations inside the houses were measured as well. A classification of houses examined, based on experiments' results was acted out in accordance with EN ISO 13790 [2]. The houses were classified into three air tightness categories, in regard to their air tightness in natural conditions and at a pressure difference of 50 Pa. Furthermore, the total frame length was estimated for the whole housing stock, and a correlation between the air tightness measurements at a pressure difference of 50Pa and the total frame length was examined, for the sample of buildings and for each air tightness category. A correlation between the airflow values, as they resulted from the fan pressurization method and the average infiltration rates, calculated by the tracer gas experiment results, has been extracted. Moreover, the effect of climate data including temperature and windiness and construction quality on the houses' infiltration characteristics has been investigated.
Science of The Total Environment, 2019
Persistence is observed between consecutive months and days for mean Tair. • An increasing tenden... more Persistence is observed between consecutive months and days for mean Tair. • An increasing tendency is observed for Tair and degree days for most months. • In winter, degree days show a decreasing trend indicating lower needs for heating.