Round Static Chimney Cowl - Full Rain Protection
92,13 €
92,13 €
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Round Static Chimney Cowl - Full Rain Protection
Round static cowl: a modular system so the chimney draws on its own
A chimney finished with an open mouth collects everything that falls on it: rainwater that carries soot down the flue, dust, leaves and nests. And when wind blows sideways, smoke comes back into the living room. This round static cowl solves it by fitting a small concrete tower onto the flue — base, intermediate pieces and cap — that covers the mouth without closing it and uses the wind itself to draw smoke upward, with no motor, no electricity and not a single moving part.
✅ Key advantages
- Venturi effect: wind enters through the open ring between pieces and is forced through a narrower section. As the passage narrows, the air speeds up and its pressure drops; that suction right above the flue mouth pulls smoke outward. The harder it blows, the better it draws.
- Three-piece modular system: a base that rests on the flue top, several intermediate pieces that form the suction chamber, and a cap that finishes the assembly. Height and diameter are combined to suit each flue.
- Minimum of four intermediate pieces: that's the chamber height needed for the Venturi effect to really work. With fewer, the assembly keeps out the rain but barely improves the draft.
- Round geometry, no dead corners: air flows around the assembly with no turbulence in corners, and water runs off the whole circumference instead of pooling.
- Drip edges on the cap and the base: the grooved edge cuts off water and lets it fall clear, so it doesn't run down the lower pieces or stain the pillar with soot streaks.
- Concrete with no internal reinforcement: there's no steel inside for acidic smoke condensates to corrode. Nothing to paint or replace: no maintenance needed.
🏗️ Recommended applications
- Wood-burning fireplaces, stoves and inserts in single-family homes.
- Outlets for oil, gas or biomass boilers suffering wind-driven backflow.
- Ventilation and extraction ducts finishing at roof level.
- Renovating chimneys that get dirty or drip soot from an open mouth.
- Homes in windy, coastal or mountain areas, where downdrafts are common.
📋 Technical specifications
- Material: concrete, no internal reinforcement.
- Caps: Ø 40 × 4.5 cm (11.2 kg) and Ø 50 × 4.5 cm (16.7 kg).
- Intermediate pieces: Ø 30 × 8 cm (4.2 kg) and Ø 46 × 9.2 cm (9.3 kg).
- Bases: 38 × 38 × 8 cm (9.5 kg), 50 × 50 × 9.5 cm (17.9 kg), 65 × 65 × 9.2 cm (35.6 kg) and 76 × 56 × 9.2 cm (36.6 kg).
- Distance between drip edges on the Ø 40 cm cap: 35.5 cm.
- Units per pallet for the Ø 40 cm cap: 30.
- Recommended set composition: 1 base + at least 4 intermediate pieces + 1 cap.
- Colors available: White and Natural Grey.
- Use: outdoor, on the roof.
- Packaging: single unit or pallet.
🧰 Installation
- Measure the internal flue section and choose the base whose opening covers it completely with firm support all around.
- Level the top of the flue with mortar until you have a flat, horizontal surface.
- Bed the base on fresh mortar, centered over the opening, and check the level in both directions.
- Stack the intermediate pieces — at least four — aligning the axes and leaving the air-passage rings between them clear.
- Finish with the cap and seal only the support joints. Don't fill in the open rings: they're what create the suction.
- Let it cure for 24-48 hours before lighting the appliance.
📦 Available formats
- Caps of Ø 40 × 4.5 cm and Ø 50 × 4.5 cm, in White or Natural Grey.
- Intermediate pieces of Ø 30 × 8 cm and Ø 46 × 9.2 cm, in White or Natural Grey.
- Bases of 38 × 38 × 8 cm, 50 × 50 × 9.5 cm, 65 × 65 × 9.2 cm and 76 × 56 × 9.2 cm.
- All formats, in single-unit or pallet packaging.
💡 Professional tip: the costliest mistake with this system is building it too short. People buy the base, the cap and one or two intermediate pieces — the parts that "show" — and the assembly ends up as a rain cover with no real suction. You need at least four intermediate pieces for the chamber to be tall enough for the Venturi effect to work. Also order one extra piece per chimney: these are thin-edged pieces that chip easily going up to the roof, and a second trip for just one piece costs more than the piece itself. And check the mouth height: as good practice in Spain, it should sit 1 m above the highest point within a 2 m radius.
Frequently Asked Questions
¿Qué piezas necesito para montar un aspirador completo?
Una base, cuatro piezas intermedias como mínimo y un sombrero. Las tres se piden por separado porque cada tiro necesita una combinación distinta.
¿Por qué cuatro intermedias y no dos?
Porque el efecto Venturi necesita altura de cámara. Con una o dos piezas el conjunto tapa la lluvia, pero no genera depresión suficiente para mejorar el tiro.
¿Cómo puede mejorar el tiro sin motor?
El viento pasa por los anillos abiertos entre piezas y se estrecha; al acelerar pierde presión y crea una succión sobre la boca del conducto que arrastra el humo hacia arriba. Es puramente aerodinámico.
¿Vale cualquier base para cualquier chimenea?
No. La base se elige por la sección interior del tiro: su hueco debe cubrirlo por completo y apoyar en firme en todo el perímetro. Hay cuatro medidas de base precisamente por eso.
¿Entra agua por los anillos abiertos?
Prácticamente no. El sombrero cubre la vertical y los goterones perimetrales cortan el agua en el canto, obligándola a caer al vacío en lugar de resbalar hacia dentro.
¿Se oxida o pide mantenimiento?
No. El hormigón no lleva armadura de acero, así que los condensados ácidos del humo y la lluvia no tienen hierro que atacar.
¿Redondo o cuadrado?
Es una decisión estética y de sección de tiro. El redondo evita esquinas muertas y reparte mejor el agua; el cuadrado encaja mejor sobre pilares de fábrica de ladrillo vistos.
¿A qué altura debe quedar la boca?
Como buena práctica habitual en España, 1 m por encima del punto más alto que haya en un radio de 2 m.