BPH2: Indoor comfort and link with outdoor conditions
Indoor-outdoor environmental coupling and exposure risk to extreme heat and poor air quality during heat waves
1Portland State University, United States of America; 2National Center for Atmospheric Research, United States of America; 3Houston Department of Health and Human Services, United States of America
Mortality and morbidity associated with extreme summer heat and poor air quality continues to be one of the most pressing human health challenges in cities and is likely to be exacerbated in the future due to urban growth and climate change. While traditional epidemiological studies of the health effects of heat and air quality focus on outdoor environmental measurements, typical urban residents spend more than 85% of their time indoors—and some of the most vulnerable populations (e.g., the elderly) spend an even higher fraction of time indoors. While the indoor environment is coupled with the outdoor environment there are key differences both in terms of air quality and thermal conditions. With respect to thermal environment, for buildings without air conditioning, this coupling includes variations in indoor air temperature that depend on building construction characteristics, location within building (e.g. top floor, south façade), occupant behavior, internal loads, ventilation, and infiltration. Indoor air quality, on the other hand, is driven by the relative magnitude of each mode of air exchange (e.g. infiltration vs. filtered mechanical ventilation) and emissions and secondary reactions of air pollutants indoors. Hence, there is a need to better understand the relationship between indoor and outdoor environments, and how this relationship is affected by occupant behavior and building construction and management practices. In the case of air conditioned and mechanically ventilated buildings a scenario of particular interest is that of coincident heat waves and power outages producing very unhealthy indoor environments.
This presentation will discuss a newly funded research project that addresses these issues, with an emphasis on eldercare facilities. It will introduce some of the key mechanisms that drive differences in indoor and outdoor conditions and present some early findings related to risks of coincident heat waves and power outages or equipment failures in buildings.
Effect of urban pollution on indoor air quality in energy-efficient buildings in the UK
University of Reading, United Kingdom
UK government has launched the target for reducing its greenhouse gas (GHG) emissions by 80% below 1990 levels by 2050. However, half of the CO2 emissions results from building sector. Naturally, promotion of energy efficiency measures for the new-built as well as refurbished buildings is the key factor to achieve such ambitious and stringent goal of carbon reduction apart from low-carbon power generation and behavioral change. Increasing the air-tightness and therefore reducing heat loss in winter is one of the important energy-efficient measures being implemented in the UK. There are two views currently in relation to the impact of insulation and airtightness on the indoor air quality and health. One believes increases in air-tightness will degrade the indoor air quality due to the insufficient ventilation, and the other holds the view that higher airtightness will minimize indoor exposure by providing more protection from the ingress of outdoor pollutants. These two views sound contradictory but both are based on reasonable ground. In this paper, we hope to shed some lights on this issue by using UK as a case study. We developed a simple one-compartment model to investigate how the urban pollution in different urban districts in London affects the indoor air quality in London dwellings. The results reveal that the current trend toward more airtight dwellings by adopting Passivhaus standard in UK may have two sides. It can greatly improve indoor air quality for the buildings located the urban centers with low or light indoor sources by enhance the protection of ingress of outdoor pollutants. However, it may cause problems in some rural dwellings with high indoor pollutant source.
INFLUENCE OF PHYSICAL PROPERTIES OF VERTICAL WALL SURFACES ON HUMAN THERMAL SENSATION BASED ON FIELD MEASUREMENTS AND MICROCLIMATE SIMULATION
1Shimizu Corporation, Japan; 2Tohoku University
In recent years, various countermeasures, such as greening, reflective painting, and ventilation paths, have been launched against Urban Heat Island phenomenon. One of the major purposes of these countermeasures is to create acceptable or tolerable thermal environments inside a warmed urban area. Thus, the performance of countermeasures should be assessed based on human thermal sensation as well as air temperature reduction. Previous studies have shown that radiation has a great influence on outdoor thermal sensation in summer. Therefore, the physical properties of building cladding materials in relation to radiation are important factors for thermal sensation in pedestrian space. Furthermore, considering the shape of the human body, the physical properties of vertical wall surfaces have more influence on thermal sensation in pedestrian spaces than those of horizontal wall surfaces. However, the properties of building cladding materials for walls have been mainly studied for reducing the heating and cooling loads of indoor spaces. Thus, knowledge of the influence of the modification of physical properties of building cladding materials on outdoor thermal sensation must be accumulated.
In order to clarify the influence of the modification of physical properties of building cladding materials on outdoor thermal sensation, field measurements were carried out at the COSMO (Comprehensive Outdoor Scale MOdel) site, Japan, in the summer of 2011. Three types of vertical wall surfaces, i.e., concrete, greening, and high reflective material, were set up, and surface temperature, air temperature, wind velocity, and three-dimensional radiant heat transport near each wall were measured. Additionally, the radiation and conduction simulations were conducted for the same area as the field measurements. Measured data was used to validate the simulation.
Calculated values of surface temperature agreed fairly well with the measured value in terms of peak position. The estimated absorbed radiation by a human body at the center of the canopy layer was compared. Although slight discrepancies between calculated and measured values were observed, these differences fell within 5% of the total absorbed radiation value.
The surfaces made of greening and high reflective material were found to almost always be cooler than the concrete surface, but the high reflective surface heated the ground and wall surfaces of neighboring buildings more than the others since it reflected more short-wave radiation. It was estimated that a human body standing near the high reflective surface would absorb the radiant heat more than when standing near the concrete, and among the three cases compared here, the radiant environment was evaluated to be the worst for the high reflective surface.