12
DOWN DRAUGHTS
However well designed, constructed and positioned,
the satisfactory performance of the flue can be
adversely affected by down draught caused by
nearby hills, adjacent tall buildings or trees. These
can deflect wind to blow directly down the flue to
create a zone of high pressure over the terminal. A
suitable anti-down draught terminal or cowl will usu-
ally effectively combat direct down blow but no cowl
is likely to prevent down draught due to a high pres-
sure zone. Ensure that any cowl used will not
restrict the flue exit or cause excessive back pres-
sure (See fig. 17) Refer to BS 5410.
Fig. 15
Fig. 16
Fig. 17
Air Inlet Blanking Plate
