Cowl (chimney)

The chimney cap (also eating head, Austro Fireplace head ) is the part of the (domestic ) chimney that protrudes visible above the roof also. About him the stack gases are discharged into the atmosphere. As a visible building component it affects the building perception. It comprises at least a shank and a mouth. Additional ingredients may be a cover plate, a head cover or an essay.

Technical Requirements

The free flow of the exhaust gases should not be hindered, the mouth structure should therefore have no significant stenosis, an optionally mounted protection against the ingress of precipitation must have a minimum distance to the mouth.

To minimize train debilitating effects of wind on the mouth region of the estuary are running higher than surrounding roof components.

From the exiting exhaust gases do not endanger residents or neighbors may go out, the mouth is therefore higher than execute surrounding windows, dormer windows or balconies.

The chimney cap must be prepared so as to not jeopardize the static wind loads. He must not have any loose parts.

If no upper possibility of purification of the chimney sweep is installed on the roof, the mouth area of the chimney sweep must be easily accessible without risk. If the chimney head protrudes high above the roof skin, another cleaning port must be installed on the roof if necessary.

Construction and components

Shaft

The shank is traditionally made of brick or rubble stone. Modern, brick chimneys are usually made of mantle rocks, possibly a layer of insulation inside and possibly an exhaust pipe leading interior. As materials for cladding stones fines lightweight concrete, concrete, crushed brick, vermiculite, calcium silicate boards rare limestone, gas concrete, clay are common. The cladding stones should be protected through the roof against the elements by a panel.

The following types of cladding are common in modern chimneys:

• Panel with a finished head, for example, fiber cement boards

• Verschieferung with slate tiles or sheeting with galvanized steel sheets or aluminum sheets

• Walling with brick

• Plaster

Cover

Cover plates protect the mouth area from weather influence. In addition, they can use the static properties of the chimney head improve (weight input) as well as serve as a static -leading receiver for essays or covers. In modern, ventilated chimneys, the cover plate can take an additional function of the combustion air introduction or exhaust air ducting with. Cover plates are commonly made ​​of concrete craftsmanship on site or prefabricated Betonabdeckplatten used. Modern variants may also be made ​​of fiber cement sheets or stainless steel sheets. These plates can be performed with a drip edge, so that rain water to the fairing drips over.

Mouth

The chimney top is the area of the head where the exhaust gases are directed into the open. In modern chimneys to an exhaust leading inner pipe which terminates below the cover plate, the opening area can be formed with a Dehnfugenblech, which is introduced between the (concrete ) the cover plate and the inner tube and compensates for the linear expansion of the temperature-stressed Innrohres. Other modern versions run the exhaust leading inner tube through the cover plate through and protect the resulting annular gap between the pipe and cover with a covering skirt or a rain collar against the ingress of rain water. Covering apron or rain collars are attached to the exhaust pipe leading interior.

Chimney cover

To prevent the infiltration of water into the mouth of chimney caps are used in flat form called Meidinger disc ( after Heinrich Meidinger ), in a corrugated form as Napoleon hat. The cover can be anchored on the cover plate, or be inserted into the exhaust port. The distance between the cover plate and mouth should be at least half the clear inner dimension and inner diameter of the chimney, in order not to impede the free flow. Special case of rain caps on chimneys where heat generators are connected with low exhaust gas temperatures: The water vapor contained in the exhaust gases can condense on the cover in very cold weather. This icing may arise that impede the free flow of exhaust gases.

Chimney cowls

In order to improve the chimney function to protect the building fabric or upgrade to the look of the chimney head chimney pots are used. Differences are rigid and structures with moving parts. Material side, steel towers, concrete and ceramic essays essays are distinguished.

Steel towers are made from galvanized steel sheets or stainless steels. An advantage is the ease of manufacture and assembly, a disadvantage of galvanized structures, the short lifetime (rust) and the optics.

Concrete essays are mortared on the cover, are usually very short and often have lateral lamella- like opening. Advantageously, the cheap price, adversely affect the short service life because sulphurous fumes can attack the concrete.

Ceramic chimney caps have an extremely long service life because acid resistant and are visually appealing. The disadvantage is the higher installation costs.

Technical function of the rigid attachments: By extending the effective stack height a Zugverbesserung is achieved. By moving the orifice outlet to the top towards the ridge of the disturbing effects of wind exhaust outlet can be avoided. By a slight cross-sectional constrictions of the exhaust outlet can be accelerated and thus a better solution of the plume can be achieved even in windy conditions. By lamellar formation of essays horizontally inflowing wind can also speed up the exhaust outlet. Characterized in that the exhaust outlet is effected substantially over the cover plate, thermal drawbacks, by heating of the cover plate on summer days, disturbing wind turbulence in the region of the chimney head shank and the flashback of chemically aggressive gas in the (concrete) cover plate or the shaft can be reduced.

Technical function of moving essays: These are often fitted at the mouth with rotating Lammelenkugeln or rolls. These generate with wind an additional negative pressure, so that the exhaust velocity to be increased in the chimney. Without this wind rotary attachments can, however, be a train obstructing flow resistance. Another embodiment has the mouth area a wind shield that automatically aligns itself against the wind direction. This is intended annoying wind influences are avoided.

• Chimney heads, embodiments

Chimney pot with cover and wind chime in Lemmer, The Netherlands

Chimney head with brick cover in Bruges, Belgium

Chimney heads in Istandbul, Turkey

Head detail, Dun -Sur -Meuse, France

Ceramic head extensions in Chester, England