The chimney stack is a device fitted on the top of the chimney that is designed to
aid dispersion of the products of combustion in the atmosphere.
The chimney stack must comply with the following requirements:
- it must have an internal section and shape the same as the flue (A);
- it must have a useful outlet section (B) of not less than twice that of the flue (A);
- the part of the chimney that emerges from the roof or remains in contact with the
outside (e.g. in the case of a flat roof), must be covered with brick or tile elements
and in any case well insulated;
- it must be built in such a way as to prevent the penetration of rain, snow and
foreign matter into the flue and to ensure that in the event of winds from all
directions and angle, discharge of the combustion products is assured (chimney
stack with down-draught cowl).
Recommended distances for correct chimney operation.
To ensure trouble-free operation of the chimney and allow correct dilution of the
products of combustion in the air, the chimney stack must be installed at the
distances given below:
- 6-8 metres from any buildings or other obstacles that are higher than the
chimney stack;
- 50 centimetres higher than any obstacles located at a distance less than 5
metres;
- outside the reflux area. The size and shape of this area differ according to the
angle of inclination of the roof and it is therefore necessary to adopt the minimum
heights shown below.
Example:
Check the slope of the roof (
column
α
), and the anticipated distance of
the chimney stack from the axis of the ridge (
column A
), if the distance is greater
than “
A
” the height of the chimney stack may be read in (
column H
); if the distance
is less than “
A
” the chimney stack must rise above the ridge by 0.5 metres.
DT2010025-03
1.3 ChIMNEy STACk
A
B*
* B it is twice
of to A
6-8 m
FLAT ROOF
5 m or less
5 m or less
over 5 m
0.50 m
0.50 m
SLOPING ROOF
height of reflux
area Z
distance more than A
H min
distance
0.50 m above the ridge
ridge axis
at least A
α
REFLUX
AREA
B
B
A
Fig. 7
Fig. 9
Fig. 10
Fig. 11
Fig. 8
Pitch of the roof
Horizontal width of reflux area
from ridge axis
Minimum height of outlet
from roof
Height of reflux area
α
A
H
Z
15°
1.85 m
1.00 m
0.50 m
30°
1.50 m
1.30 m
0.80 m
45°
1.30 m
2.00 m
1.50 m
60°
1.20 m
2.60 m
2.10 m
H07026300 / DT2000786 – 00
6
English
DT2030051-00
DT2030052-00
DT2030053-00
DT2030192-00
DT2030191-00
