Extract and Supply Air Flow Rates in a Large Office
Building Before and After Balancing
Marianna
Tuomainen1, Olli Seppänen1, Jarek Kurnitski1 and
Raimo Niemelä2
1Laboratory
of Heating, Ventilating and Air-Conditioning, Helsinki University of
Technology
2Finnish
Institute of Occupational Health
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Abstract
One of the two air
distribution systems serving the office rooms of a 25-year-old large
office building was balanced in autumn 2002. The supply and extract air
flow rates of 173 office rooms were measured before and after balancing.
Before balancing, the air flow rates varied considerably from room to room
and many of the office rooms were over pressurised. The average extract
air flow rate in the whole of the building was 20.7 L/s.person and the
standard deviation 11.0 L/s.person. The aim of the balancing process was
to meet the design values dating from 1978. The original air distribution
plan was very disparate, presumably taking into consideration both room
size and number of occupants in the room. Balancing achieved the design
air flow rates remarkably well but the person-specific air flow values
still varied considerably between the office rooms. After balancing, the
average extract air flow rate was 29.3 L/s.person and the standard
deviation 13.6 L/s.person. The paper discusses whether design air flow
values should be followed when the occupancy within the building has
changed and whether energy saving aspects should be taken into account.
Balancing is recommended after duct cleaning or major building renovations
to accommodate for changes that have taken place in the air distribution
system.
Key words: air
distribution, air flow rate measurements, balancing, office building,
pressure conditions, ventilation.
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