Thermal Diagnostics of Natural Ventilation in Buildings: An Integrated Approach

Abstract

Diagnostics of natural ventilation in buildings is problematic, as the airflow rate changes considerably over time. One constant average airflow is usually assumed when calculating energy demand for a building, however, such a simplification could be fraught with considerable error. The paper describes a comprehensive methodology for the diagnostics of a natural ventilation system in a building and its practical application. Based on in situ measurements and simulations in two existing buildings (dwelling house and school) in Poland, the real values of the ventilating airflows were analyzed and resulting heat demand was compared with the design values. The pros and cons of various methods for evaluation of natural ventilation are discussed. The real airflow was determined by measurements in a ventilation grille or by a tracer gas concentration decay method. The airtightness of the buildings’ envelope was evaluated based on the fan pressurization test. The last stage entailed computer simulations of air exchange in buildings using CONTAM software. The multizone models of the buildings were calibrated and verified with existing measured data. Measured airflow in a multifamily house was small and substantially deviated from the Polish standard. In case of a school, the air flow rate amounted to an average of 10% of the required value. Calculation of the heat demand for ventilation based on the standard value of the airflow led to a considerable overestimation of this value in relation to the real consumption. In the analyzed cases, the difference was 40% for the school and 30% for the residential building.

COVID-19, the Built Environment, and Health

“…in New York found that crowded home environments-a typical feature of poor neighborhoods-raised the risk of airborne disease transmission in pregnant women (Emeruwa et al 2020). In some studies, crowded neighborhoods had higher transmission rates than less crowded neighborhoods (Kadi and Khelfaoui 2020;Zhang and Schwartz 2020)-a pressing challenge in such cities as Mumbai, Nairobi, and Karachi, where substantial portions of the city consist of slums.…”

Quantification of Air Change Rate by Selected Methods in a Typical Apartment Building

“…Several contributions have been devoted to this issue, focused on natural air exchange, in the recent period [41][42][43][44]. In paper [45], the focus is on air exchange in the summer when considering energy savings.…”

Analysis of Heat Demand and Thermal Comfort in Naturally Ventilated Single-Family Houses of Various Constructions

“…V inf -infiltration airflow, m 3 /s, ELA -effective leakage area at 4 Pa pressure differential, cm 2 , C s -coefficient for stack-induced infiltration, 0.00029 (dm 3 /s) 2 /(cm 4 K), ΔT -temperature diff erence between zone air and outdoor air, K, C w -coefficient for wind-induced infiltration, 0.000231 (dm 3 /s) 2 /(cm 4 (m/s) 2 ), w -local wind speed, m/s. For calculations as the leakage areas were adopted: C -flow coefficient, m 3 /(hPa 0.67 ), a -airtightness factor, m 3 /(mhPa 0.67 ), l -length of the window leakages, m. The value of the airtightness factor for the windows was assumed at the level of 0.3 m 3 /(mhPa 0.67 ) based on available studies on the airtightness of Polish residential buildings [21,22]. The length of the window leakages was the total perimeter of each window sash.…”