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Airtightness, air movement and indoor air quality in Atlantic region high rise apartment buildings.

CMHC, 1991
high rise buildings | air movement | air tightness | indoor air quality
Bibliographic info: Canada Mortgage and Housing Corporation, Technical Series 91-203
Languages: English Pages (count): 294

This report presents the findings of a field investigation and assessment into air tightness, air movement and indoor air quality conducted on two ( 2) residential high-rise apartment buildings located in St. John's, Newfoundland.


The investigations were performed in three phases. The first phase involved a building assessment in which the likely candidates for the study were screened to meet selected criteria. The second phase involved a pollution source identification process in which a building survey was conducted with the occupants to identify possible pollutants within the building. The third phase involved physical testing of the selected buildings during the months of February and March 1991 to establish air tightness, air movement and air quality.


Two buildings were selected during Phase 1, Building 1 a seven (7) storey building with 51 apartments, Building 2 a six (6) storey building with 65 apartments. Phase II survey of the occupants in Building 1 revealed only minor problems on the first level while most complaints related to the air infiltration problems in the structure. In Building 2, similar results related to air quality and air tightness were recorded.


Phase III testing was conducted in both buildings. The air tightness of exterior walls and between storey slabs was assessed using a storey by storey fan depressurization technique. Certain portions of the building were depressurized while flow rates at designated external pressure differentials were measured on the test storey. Contaminant airflow patterns within the buildings were studied using a tracer gas technique. A specified volume of tracer gas was instantaneously released at a specified location within the building. Following this release, air samples were taken at specified locations through the building at pre-determined time intervals. Air quality was assessed by monitoring the levels of various pollutants, which had previously been identified during a building assessment, at various locations through the building.


From the Phase III testing, it was concluded that in both Building 1 and Building 2 air infiltration rates exist which are higher than NRC and international standards for air infiltration. Building 1 is substantially leakier than Building 2. Outside weather conditions dominate air movement in the buildings by promoting ·travel up through the building through garbage chutes, stairwells and elevator shafts by stack effect in Building 1. Occupant movement promotes air movement in Building 2 as opposed to weather conditions due to the lower infiltration in this building.


During testing for indoor air quality, it was observed in Building 1, co2 , Radon and relative humidities to be lower than Building 2 due to the relative tightness of Building 1 being less than Building 2. However, all contaminant levels, except Total Suspended Particulates (TSP) in smoker's apartment, were within government recommended guidelines. No testing of the, effectiveness of ventilation systems was performed during this project.


Air change rates were observed to be 6.5 times greater than the normal value of 1.5 air changes per hour used for design purposes (wind speed = 48 km/h and 75 Pa pressure difference for St . John's).


Possible causes include inadequately sealing backdraft dampers, or other mechanical system components. The testing procedures did not include the complete sealing of all air diffusion equipment which can contribute significantly to high air infiltration rates. In Building 1 extreme care was exercised to meticulously seal all openings for these systems and still higher air infiltration was observed.


 


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