Occupants’ interactions with windows in 8 residential apartments in Beijing and Nanjing,China

Occupants’ interactions with windows influence both building energy consumption and exposure to airborne pollutants indoors. Occupants’ window opening behavior varies from region to region due to physical environmental factors and social reasons. China is now confronting severe atmospheric pollution, which may affect occupants’ window opening behaviors. A field study was conducted in 8 naturally ventilated residential apartments in Beijing and Nanjing, China. This involved periodically monitoring window states of eight residential apartments within each season from October 2013 to December 2014 by magnetic induction devices (TJHY, CKJM-1). Relationships between the probability of window opening (p) and explanatory variables, including outdoor air temperature (t _o), outdoor relative humidity (RH), outdoor wind speed (V _s), and ambient PM2.5 (particles with aerodynamic diameter less than 2.5 microns) concentrations (C _p), were analyzed. Stochastic models of occupants’ interactions with windows in monitored residences were established via univariate and multivariate linear logistic regression for both cities. According to the results, t _o is the most important explanatory variable affecting occupants’ interactions with windows in monitored residences. The best multivariate linear logistic model result from the “backward selection” procedure based on “Akaike Information Criterion” (AIC) includes t _o, RH, V _s and C _p as explanatory variables, which implied that outdoor air quality, represented by C _p, has become a concern affecting Chinese residents’ interactions with windows.     

Untersuchungen zum Raumklima und zur Fensterlüftung in Schulen

Investigations on indoor environmental conditions and natural ventilation in school buildings. There are more than 40,000 school buildings in Germany. Most of them are awaiting retrofitting. Retrofitting is not only intended to improve the energetic standards, but first of all to improve indoor environmental conditions for pupils and teachers. As most of German schools are not equipped with mechanical ventilation systems, natural ventilation controlled by the occupants opening the windows is the main way to maintain healthy and comfortable conditions in the classrooms. For that purpose the influence of window opening behaviour of the occupants on the indoor environment was measured in two German schools. Temperature and carbon dioxide concentration of the indoor air as well as the outdoor climate conditions were measured. In one school the frequency of window opening was recorded. Besides high CO₂‐concentrations especially during winter, some of the investigated classrooms are additionally to cold in winter or to hot in summer. Some classrooms do not have a shading device or the shading device is insufficient or it constricts the ventilation of the room. Windows are used as controls in some degree during lessons and during the breaks. But windows get closed after lessons and stay closed until next morning. There is no night or early morning ventilation in summer. A significant weak to moderate positive correlation between total open window ratio and indoor temperature has been found. Correlation between total open window ratio and outdoor temperature is not significant in most cases or show a weak correlation coefficient.     

Case study of window opening behavior using field measurement results

Window opening behavior has significant influences on indoor environment and energy consumption in residential buildings. As a response to indoor environment, the control mechanism (window and interior door open/closed) should be studied first by comprehensive understanding of the variation of indoor environmental conditions. For this reason, a field measurement of environmental conditions was carried out in five representative apartments in Beijing from April to May in 2010. By comparison analyses of the field measurement results, major findings are as follows: (1) the concentration of room CO₂ can be the best predictor of occupant behavior, also window opening behavior, in residential buildings; (2) the variation in indoor air quality mainly results from large variation in window opening behavior; (3) apart from indoor and outdoor thermal environment, indoor air quality as well as occupants’ presence at room have also considerable effect on window opening behavior; (4) while defining window opening behavior for one room in residential building, it is necessary to take the window adjustment of its connecting room and the adjustment of the connecting door into consideration due to air diffusion between the two connecting rooms.     

Using results from field surveys to predict the effect of open windows on thermal comfort and energy use in buildings

Windows are one of the major means by which building occupants control the indoor environment. This research uses results from field surveys to formulate a method for simulation of office buildings to include the effects of window opening behaviour on comfort and energy use. The paper focuses on: (1) what is general window opening behaviour? (2) how can we frame an “adaptive algorithm” to predict whether windows are open? (3) how can the algorithm be used within a simulation to allow the effects of window opening on comfort and energy use to be quantified? We have found that: (1) the proportion of windows open depends on indoor and outdoor conditions, (2) logistic regression analysis can be used to formulate an adaptive algorithm to predict the likelihood that windows are open, (3) the algorithm when embedded in simulation software provides insights not available using more usual simulation methods and allows the quantification of the effect of building design on window opening behaviour, occupant comfort and building energy use.     

Towards a model of user behaviour regarding the manual control of windows in office buildings

This paper presents the results of a field study of manual control of windows which has been carried out in 21 individual offices within the Fraunhofer Institute's building in Freiburg, Germany, from July 2002 to July 2003. Window status, occupancy, indoor and outdoor climatic conditions were measured every minute. Previous research findings are validated and extended by the results of this field study. The analysis of user behaviour reveals a strong correlation between the percentage of open windows and the time of year, outdoor temperature and building occupancy patterns. Most window opening is connected with the arrival of a person. Based on the results, a preliminary user model is proposed to simulate and predict window status in office buildings with varying outdoor temperature and occupancy.     

Development of an adaptive window-opening algorithm to predict the thermal comfort,energy use and overheating in buildings

This investigation of the window-opening data from extensive field surveys in UK office buildings demonstrates: (1) how people control the indoor environment by opening windows; (2) the cooling potential of opening windows; and (3) the use of an ‘adaptive algorithm’ for predicting window-opening behaviour for thermal simulation in ESP-r. It was found that when the window was open the mean indoor and outdoor temperatures were higher than when closed, but it was shown that nonetheless there was a useful cooling effect from opening a window. The adaptive algorithm for window-opening behaviour was then used in thermal simulation studies for some typical office designs. The thermal simulation results were in general agreement with the findings of the field surveys. The adaptive algorithm is shown to provide insights not available using non adaptive simulation methods and can assist in achieving more comfortable, lower energy buildings while avoiding overheating.     

Indoor birch pollen concentrations differ with ventilation scheme,room location,and meteorological factors

Indoor pollen concentrations are an underestimated human health issue. In this study, we measured hourly indoor birch pollen concentrations on 8 days in April 2015 with portable pollen traps in five rooms of a university building at Freising, Germany. These data were compared to the respective outdoor values right in front of the rooms and to background pollen data. The rooms were characterized by different aspects and window ventilation schemes. Meteorological data were equally measured directly in front of the windows. Outdoor concentration could be partly explained with phenological data of 56 birches in the surrounding showing concurrent high numbers of trees attaining flowering stages. Indoor pollen concentrations were lower than outdoor concentrations: mean indoor/outdoor (I/O) ratio was highest in a room with fully opened window and additional mechanical ventilation (.75), followed by rooms with fully opened windows (.35, .12) and lowest in neighboring rooms with tilted window (.19) or windows only opened for short ventilation (.07). Hourly I/O ratios depended on meteorology and increased with outside temperature and wind speed oriented perpendicular to the window opening. Indoor concentrations additionally depended on the previously measured concentrations, indicating accumulation of pollen inside the rooms even after the full flowering period.     

Predictors of summertime heat index levels in New York City apartments

During heat waves, fatal overexposure to heat most often occurs at home. It is not known how factors such as building size, floor level, and different types of air conditioning (AC) contribute to excess indoor heat. We monitored indoor temperature and humidity in 36 apartments in New York City during summers 2014 and 2015 and used these values to calculate the indoor heat index (HI). We investigated the role of AC type and building‐level factors on indoor HI using multilevel regression models. Thirty‐four of 36 homes had AC. Central and ductless AC types were associated with the coolest indoor conditions; homes with window and portable AC were significantly warmer. Apartments on the top floor of a building were significantly hotter during heat advisory periods than other apartments regardless of the presence of AC. High indoor HI levels persisted in some homes for approximately 1 day following the end of the two heat advisory periods. We provide concrete evidence of higher heat levels in top floor apartments and in homes with certain types of AC. High heat levels that persist indoors after outdoor heat has subsided may present an underappreciated public health risk.     

Experimental investigation of the air flow and indoor carbon dioxide concentration in classrooms with intermittent natural ventilation

Air flow and the associated indoor carbon dioxide concentrations have been extensively monitored in 62 classrooms of 27 naturally ventilated schools in Athens, Greece. The specific ventilation patterns as well as the associated carbon dioxide concentrations, before, during and after the teaching period are analysed in detail. During the teaching period, only 23% of the measured classrooms presented a flow rate higher than the recommended value of 8 l/p/s while the mean daily fluctuation was close to 40%. About, 52% of the classrooms presented a mean indoor CO₂ concentration higher than 1000 ppm. The specific experimental data have been compared against existing ventilation rates and carbon dioxide concentrations using published information from 287 classrooms of 182 naturally ventilated schools and 900 classrooms from 220 mechanically ventilated schools. The relation between the air flow rates and the corresponding indoor carbon dioxide is analysed and then compared to the existing data from naturally and mechanically ventilated schools. It is found that all three data sets present a CO₂ concentration equal to 1000 ppm for air flows around 8 l/p/s. Specific adaptive actions to improve the indoor environmental quality have been recorded and the impact of indoor and ambient temperatures as well as of the carbon dioxide concentration on window opening is analysed in detail. A clear relation is found, between the indoor temperature at which the adapting action takes place and the resulting air flow rate. In parallel, a statistically significant relation between window opening and the indoor–outdoor temperature difference has been established.     

Factors affecting wavelength-resolved ultraviolet irradiance indoors and their impacts on indoor photochemistry

We measured wavelength-resolved ultraviolet (UV) irradiance in multiple indoor environments and quantified the effects of variables such as light source, solar angles, cloud cover, window type, and electric light color temperature on indoor photon fluxes. The majority of the 77 windows and window samples investigated completely attenuated sunlight at wavelengths shorter than 320 nm; despite variations among individual windows leading to differences in indoor HONO photolysis rate constants (J_HONO) and local hydroxyl radical (OH) concentrations of up to a factor of 50, wavelength-resolved transmittance was similar between windows in residential and non-residential buildings. We report mathematical relationships that predict indoor solar UV irradiance as a function of solar zenith angle, incident angle of sunlight on windows, and distance from windows and surfaces for direct and diffuse sunlight. Using these relationships, we predict elevated indoor steady-state OH concentrations (0.80–7.4 × 10⁶ molec cm⁻³) under illumination by direct and diffuse sunlight and fluorescent tubes near windows or light sources. However, elevated OH concentrations at 1 m from the source are only predicted under direct sunlight. We predict that reflections from indoor surfaces will have minor contributions to room-averaged indoor UV irradiance. These results may improve parameterization of indoor chemistry models.     

Size-resolved dynamics of indoor and outdoor fluorescent biological aerosol particles in a bedroom: A one-month case study in Singapore

This study evaluated the interrelations between indoor and outdoor bioaerosols in a bedroom under a living condition. Two wideband integrated bioaerosol sensors were utilized to measure indoor and outdoor particulate matter (PM) and fluorescent biological airborne particles (FBAPs), which were within a size range of 0.5-20 μm. Throughout this one-month case study, the median proportion of FBAPs in PM by number was 19% (5%; the interquartile range, hereafter) and 17% (3%) for indoors and outdoors, respectively, and those by mass were 78% (12%) and 55% (9%). According to the size-resolved data, FBAPs dominated above 2 and 3.5 μm indoors and outdoors, respectively. Comparing indoor upon outdoor ratios among occupancy and window conditions, the indoor FBAPs larger than 3.16 μm were dominated by indoor sources, while non-FBAPs were mainly from outdoors. The occupant dominated the indoor source of both FBAPs and non-FBAPs. Under awake and asleep, count- and mass-based mean emission rates were 45.9 and 18.7 × 10⁶ #/h and 5.02 and 2.83 mg/h, respectively. Based on indoor activities and local outdoor air quality in Singapore, this study recommended opening the window when awake and closing it during sleep to lower indoor bioaerosol exposure.     

The modifying effect of the building envelope on population exposure to PM2.5 from outdoor sources

A number of studies have estimated population exposure to PM_2.5 by examining modeled or measured outdoor PM_2.5 levels. However, few have taken into account the mediating effects of building characteristics on the ingress of PM_2.5 from outdoor sources and its impact on population exposure in the indoor domestic environment. This study describes how building simulation can be used to determine the indoor concentration of outdoor‐sourced pollution for different housing typologies and how the results can be mapped using building stock models and Geographical Information Systems software to demonstrate the modifying effect of dwellings on occupant exposure to PM_2.5 across London. Building archetypes broadly representative of those in the Greater London Authority were simulated for pollution infiltration using EnergyPlus. In addition, the influence of occupant behavior on indoor levels of PM_2.5 from outdoor sources was examined using a temperature‐dependent window‐opening scenario. Results demonstrate a range of I/O ratios of PM_2.5, with detached and semi‐detached dwellings most vulnerable to high levels of infiltration. When the results are mapped, central London shows lower I/O ratios of PM_2.5 compared with outer London, an apparent inversion of exposure most likely caused by the prevalence of flats rather than detached or semi‐detached properties.     

Relationship between outdoor and indoor air quality in eight French schools

In the frame of the French national research program PRIMEQUAL (inter-ministry program for better air quality in urban environments), measurements of outdoor and indoor pollution have been carried out in eight schools in La Rochelle (France) and its suburbs. The buildings were naturally ventilated by opening the windows, or mechanically ventilated, and showed various air permeabilities. Ozone, nitrogen oxides (NO and NO(2)), and airborne particle (particle counts within 15 size intervals ranging from 0.3 to 15 mum) concentrations were continuously monitored indoors and outdoors for two 2-week periods. The indoor humidity, temperature, CO(2) concentration (an indicator of occupancy), window openings and building permeability were also measured. The temporal profiles of indoor and outdoor concentrations show ozone and nitrogen oxides behave differently: NO and NO(2) indoor/outdoor concentration ratios (I/O) were found to vary in a range from 0.5 to 1, and from 0.88 to 1, respectively, but no correlation with building permeability was observed. On the contrary, I/O ratios of ozone vary in a range from 0 to 0.45 and seem to be strongly influenced by the building air-tightness: the more airtight the building envelope, the lower the ratio. Occupancy, through re-suspension of previously deposited particles and possible particle generation, strongly influences the indoor concentration level of airborne particles. However, this influence decreases with particle size, reflecting the way deposition velocities vary as a function of size. The influence of particle size on deposition and penetration across the building envelope is also discussed by analyzing the I/O ratios measured when the buildings were unoccupied, by comparing the indoor concentrations measured when the buildings were occupied and when they were not (O/U ratios), and by referring to previously published studies focussing on this topic. Except one case, I/O were found to vary in the range from 0.03 to 1.79. All O/U are greater than one and increase up to 100 with particle size. PRACTICAL IMPLICATIONS: Assessing children's total exposure requires the knowledge of outdoor and indoor air contaminant concentrations. The study presented here provides data on compared outdoor and indoor concentration levels in school buildings, as well as information on the parameters influencing the relationship between outdoor and indoor air quality. It may be used as a basis for estimating indoor concentrations from outdoor concentrations data, or as a first step in designing buildings sheltering children against atmospheric pollution.     

Predicting integrated thermal and acoustic performance in naturally ventilated high-rise buildings using CFD and FEM simulation

The study of ventilation windows for both natural ventilation and noise mitigation has drawn significant attention recently. This paper presents the numerical approaches to analyse the integrated thermal and acoustical performance of ventilation windows, for a residential building in tropical climate which employs double-layer noise mitigation window for natural ventilation. Given a set of outdoor wind conditions, the distributions of indoor flow and temperature fields are simulated using Computational Fluid Dynamics (CFD) model. The thermal comfort is evaluated using statistical Predicted Mean Vote (PMV) method. For the acoustic performance, noise radiation from road traffic is assumed as the noise source, and the sound insulation of building façade is simulated using Finite Element Method (FEM). From the simulation results, it is found that the thermal satisfaction response is closely related to the inlet wind temperature and speed, and the window opening size greatly affects the ventilation performance. From the case study in Singapore, during certain season, day/night time and with sufficient wind flow, the ventilation window can provide enough fresh air, maintain adequate thermal comfort and quiet acoustic environment for the occupants. The numerical approaches presented in this paper are applicable to general window design studies, and the simulation findings can be incorporated into green building planning. The advantages of using simulation approaches are highlighted and their limitations are discussed.     

A field investigation of the thermal environment and adaptive thermal behavior in bedrooms in different climate regions in China

Sleep thermal environments substantially impact sleep quality. To study the sleep thermal environment and thermal comfort in China, this study carried out on-site monitoring of thermal environmental parameters in peoples’ homes, including 166 households in five climate zones, for one year. A questionnaire survey on sleep thermal comfort and adaptive behavior was also conducted. The results showed that the indoor temperature for sleep in northern China was more than 4°C higher than that in southern China in winter, while the indoor temperatures for sleep were similar in summer. Furthermore, 70% of people were satisfied with their sleep thermal environment. Due to the use of air conditioning and window opening in various areas in summer, people were satisfied with their sleep thermal environments. Due to the lack of central heating in the southern region in winter, people feel cold and their sleep thermal environment needs further improvement. The bedding insulation in summer and winter in northern China was 1.83clo and 2.67clo, respectively, and in southern China was 2.21clo and 3.17clo, respectively. Both northern China and southern China used air conditioning only in summer. People in southern China opened their windows all year, while those in northern China opened their windows during the summer and transitional periods.     

居室热压自然通风应用探讨

采用风速法和示踪气体衰减法实测了某居室的自然通风量。得到了不同窗孔开度下的窗孔流量系数,给出了窗孔流量系数与窗孔开度的关系曲线,分析了室内外空气温差对窗孔流量系数的影响。     

炎热地区夏季窗户的热过程研究

以重庆地区为例，探讨了炎热地区夏季南向和西向窗户的太阳辐射得热问题。认为辐射得热是导致室内热环境恶化的首要原因，西向铝合金双玻窗的辐射得热高达520W／m^2，而基于室内外温差的热流最大也不超过50W／m^2；对于南向窗，太阳直射对室内热环境影响相对较小，天空散射与环境反射是窗户得热的主要来源。对炎热地区的窗户节能而言，有效控制辐射得热、采用遮阳装置是问题的关键。     

Residential air-change rates: A critical review

Air-change rate is an important parameter influencing residential air quality. This article critically assesses the state of knowledge regarding residential air-change rates, emphasizing periods of normal occupancy. Cumulatively, about 40 prior studies have measured air-change rates in approximately 10,000 homes using tracer gases, including metabolic CO₂. The central tendency of the air-change rates determined in these studies is reasonably described as lognormal with a geometric mean of 0.5 h⁻¹ and a geometric standard deviation of 2.0. However, the geometric means of individual studies vary, mainly within the range 0.2–1 h⁻¹. Air-change rates also vary with time in residences. Factors influencing the air-change rate include weather (indoor–outdoor temperature difference and wind speed), the leakiness of the building envelope, and, when present, operation of mechanical ventilation systems. Occupancy-associated factors are also important, including window opening, induced exhaust from flued combustion, and use of heating and cooling systems. Empirical and methodological challenges remain to be effectively addressed. These include clarifying the time variation of air-change rates in residences during occupancy and understanding the influence of time-varying air-change rates on tracer-gas measurement techniques. Important opportunities are available to improve understanding of air-change rates and interzonal flows as factors affecting the source-to-exposure relationships for indoor air pollutants.     

A method for assessing the performance of nanofiber films coated on window screens in reducing residential exposures to PM2.5 of outdoor origin in Beijing

Recently, many nanofiber films have been developed for air filtration applications. These films exhibit high PM_2.5 (particles with aerodynamic diameters less than 2.5 μm) removal efficiency and relatively low air resistance. Thus, coating window screens with nanofiber films may be able to mitigate residential exposure to PM_2.5 of outdoor origin. This study developed a method for assessing the performance of nanofiber window screens in reducing residential exposure to PM_2.5 of outdoor origin in Beijing. The results show that the use of selected nanofiber window screens all the time throughout the year can reduce the mean value of the annual average indoor PM_2.5 of outdoor origin by 64%‐66% for Beijing residences. However, the mean value of annual harmonic average air exchange rate when the windows are open was also reduced from 2.34 h^?1 to 0.27‐0.35 h^?1, which is far below the national standard. If the nanofiber window screens were used only when the outdoor PM_2.5 pollution was severe, the screens had less of an impact on residential natural ventilation, but the national standard still could not be met. Hence, more efforts are needed to further reduce the air resistance of nanofiber window screens in order to ensure proper residential ventilation.     

Survey of occupant behaviour and control of indoor environment in Danish dwellings

Repeated surveys of occupant control of the indoor environment were carried out in Danish dwellings from September to October 2006 and again from February to March 2007. The summer survey comprised 933 respondents and the winter survey 636 respondents. The surveys were carried out by sending out invitations to addresses obtained from a Danish register along with information on dwelling characteristics. Meteorological data was obtained from the Danish Meteorological Institute.Four control mechanisms (window open/closed, heating on/off, lighting on/off and solar shading in/not in use) were analysed separately by means of multiple logistic regression in order to quantify factors influencing occupants’ behaviour.The window opening behaviour was strongly related to the outdoor temperature. The perception of the environment and factors concerning the dwelling also impacted the window opening behaviour.The proportion of dwellings with the heating turned on was strongly related to the outdoor temperature and the presence of a wood burning stove. The solar radiation, dwelling ownership conditions and the perception of the indoor environment also affected the use of heating.The results of the statistical analyses form a basis for a definition of standard behaviour patterns which can be used to make calculation of energy consumption of buildings more accurate.