Building Services Engineering 5th Edition Handbook

Built environment 5
The perceived air pollution C i within the enclosure is found from the percentage of the
occupants who are dissatisfied with the conditions, PD, from
C i =
112
(5.98 − ln PD) 4 decipol
where PD is the percentage of the occupants who are dissatisfied (ASHRAE (1985) recommend
20%), and ln = logarithm to base e (log e ).
EXAMPLE 1.1
Calculate the outdoor air ventilation rate, from the Fanger method, that is required to
satisfy 75% of the occupants of a commercial building where none of them are smokers.
The building is located on the edge of a large town in the UK.
To satisfy 75% of the occupants, 25% are dissatisfied, so PD is 25%.
112
C i =
(5.98 − ln 25) 4 decipol
112
=
(5.98 − 3.219) 4 decipol
= 112
(2.761) 4 decipol
= 1.93 decipol
For an existing building with no smokers, G = 0.2 olf/m 2 . C o = 0.05 decipol for clean suburban
air. For 1 m 2 of office floor area
Q = 10 × G l/s m 2
C i − C o
10 × 0.2
= l/s m2
1.93 − 0.05
= 1.07 l/s m 2
EXAMPLE 1.2
A new aerobics gymnasium is being designed for the basement of a commercial building
in the City of Manchester. The room is to be 15 m long, 12 m wide and 3 m high. It has
no exterior windows. There will be between 10 and 40 simultaneous users of the facility.
There will not be any smoking and all the furnishings and building materials will have the
low-pollution emission of 0.1 olf/m 2 . At peak usage, all the occupants will be highly active.
Calculate the outdoor air ventilation rate, from the Fanger method, that will be required so
that 75% of the occupants will be satisfied. Recommend how the outdoor air ventilation
system could be controlled for energy economy and comfort. Recommend an acceptable
solution for the client.