How to coordinate kitchen ventilation specs under Spanish comunidad rules

If you design kitchens in Madrid or Barcelona towers, coordinating with a building's shared ventilation stack—the comunidad duct—can quietly drain your studio's time and your margin. Most studios already sketch out beautiful layouts in CAD or organize appliance lists in spreadsheets long before realizing the building's physical duct limits what hood can actually go in.

In Spanish apartment buildings (comunidades de propietarios), you are rarely dealing with a clean slate. You are tapping into a shared ecosystem. Specifying a kitchen hood without verifying the community's duct rules first can lead to costly retrofits, delayed handovers, and tense conversations with both the client and the building administrator.

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The technical constraint: shunt systems vs. individual extraction

In older Spanish buildings—especially those built between the 1960s and the early 2000s—you will often encounter a shunt system. This is a shared concrete duct designed to use natural convection to pull air up and out of the building. Multiple apartments vent into this single vertical stack.

[ Apartment 4 ] ---> \
[ Apartment 3 ] --->  | ---> [ Shared Shunt Duct ] ---> Roof Exhaust
[ Apartment 2 ] --->  |
[ Apartment 1 ] ---> /

If you specify a high-power extraction hood with a high flow rate—measured in cubic meters per hour, or $m^3/h$—in a shunt system, you will run into immediate trouble. The high-CFM motor will overpower the natural draft of the common duct. Instead of venting outside, your client's cooking smells will be forced backward into the kitchens or bathrooms of the neighbors upstairs or downstairs.

This violates the Código Técnico de la Edificación (CTE) and local municipal ordinances in cities like Madrid and Barcelona. Before selecting your appliance package, you must determine whether the building has a direct, individual exterior vent or a shared shunt system.

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Where the designer's scope ends and the GC's begins

To avoid finger-pointing on install day, clearly define where your responsibilities end and those of the general contractor—the contratista—begin.

The designer's scope includes:

• Specifying the appliance model, aesthetic integration, and cabinetry panels.
• Documenting the manufacturer's ventilation requirements—specifically minimum duct diameter and airflow limits.
• Outlining the aesthetic placement of the soffit or false ceiling—the falso techo.

The contractor's scope includes:

• Verifying the physical duct diameter inside the wall—often restricted to 110mm or 125mm in older buildings.
• Measuring the actual vertical clearance in the false ceiling.
• Handling the physical connection and sealing of the ductwork.

To hand off the project cleanly, document the exact duct diameter and routing path in your technical specs. Never assume the duct behind the drywall matches the standard 150mm outlet on modern high-end hoods.

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A realistic coordination scenario: the Madrid penthouse remodel

Consider a recent project—a penthouse remodel in the Chamberí neighborhood of Madrid. The client requested a sleek, integrated ceiling hood from a high-end brand like Pando or Novy, valued at €2,500. The design team initially specified an extraction model requiring a 150mm duct to move 650 $m^3/h$ of air.

During the site survey, the contractor opened the plasterboard ceiling and discovered two major physical constraints:

1. The false ceiling had only 15cm of structural clearance, while the specified inline motor required 20cm.
2. The building's shared comunidad duct was a shunt system restricted to a 110mm connection.

Duct Reduction Math & Performance Loss:
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Standard Hood Outlet:   150 mm (Area: ~17,671 mm²)
Actual Wall Connection: 110 mm (Area: ~9,503 mm²)
Area Reduction:         -46.2%
Estimated Noise Increase: +12 dB
Efficiency Loss:        ~45% static pressure drop
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Forcing 650 $m^3/h$ of air through a 110mm reducer would cause massive static pressure drop, cut the hood's efficiency by nearly half, and increase the noise level by 12 decibels—turning a quiet luxury kitchen into an incredibly loud space.

The pivot to recirculation

Instead of fighting the building's physical limits, the design team pivoted to a recirculating setup using active charcoal filters—filtros de carbón activo.

• The Hardware: A low-profile ceiling hood designed for recirculation.
• The Math: The recirculating kit added €350 to the hardware cost but saved an estimated €1,200 in complex drywall duct routing and potential building fines.
• The Lead Time: The custom hood and charcoal filter kit had a 6-week lead time from the distributor in Barcelona, which was immediately flagged on the procurement tracker to prevent installation delays.

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How to organize MEP notes and appliance specs in one place

When you are managing multiple apartment renovations, keeping technical constraints organized is a constant challenge. Most studios already track these details across spreadsheets, shared Google Docs, and long email threads with the contractor. When information is scattered, it is easy for a contractor to miss a critical note and install the wrong duct size.

Alcove lets you link your appliance specs, MEP coordination notes, and contractor sign-offs directly to the kitchen room package. By grouping your specs, drawings, and duct constraints into a single digital room folder, your team and your contractor see the technical requirements alongside the purchase order.

This keeps your technical details tied directly to the physical items being ordered—so you can spend more time on design decisions and less on copying cells or chasing vendors.

See how we do it at alcove.co.

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FAQs

Can I install a powerful extraction hood in an old Madrid apartment building?

Usually no, if the building uses a shared shunt system. High-power extraction hoods can overpower the common duct—pushing your client's kitchen fumes into neighboring apartments. In these cases, you must spec a recirculating hood with high-quality charcoal filters or a low-flow motor that complies with the comunidad guidelines.

Who is responsible if the kitchen hood does not fit the ceiling duct?

The designer is responsible for specifying an appliance that fits the aesthetic and spatial constraints provided, but the general contractor is responsible for verifying the physical duct dimensions and structural clearances before ordering. Clear documentation of these boundaries in your project specs prevents disputes.

How do I document Spanish building code (CTE) ventilation requirements for my clients?

Keep a standardized MEP checklist attached to your kitchen product packages. Document the extraction rate, duct diameter, and filter type directly alongside the appliance specifications so the client understands why a specific—and sometimes less powerful—model was selected.