ventilation-and-chimney-systems

Building Services · Interior Architecture · Design Studio · Professional Practice · Environmental Design

Ventilation and Chimney Systems in Kitchens

Effective ventilation is not a luxury in a kitchen; it is a critical system for maintaining a healthy and comfortable indoor environment. Cooking processes release a mixture of heat, steam, grease particles, and odors. Without proper ventilation, these pollutants can degrade indoor air quality, cause damage to finishes, and create an unpleasant living space.

1. The Purpose of Kitchen Ventilation

• Removal of Pollutants: The primary function is to capture and exhaust airborne grease, smoke, and combustion byproducts (from gas stoves) at their source.
• Odor Control: It removes cooking smells, preventing them from spreading throughout the home.
• Heat and Steam Removal: It helps to control the temperature and humidity levels in the kitchen, enhancing comfort.
• Preservation of Finishes: By removing grease-laden air, a good ventilation system prevents the buildup of sticky, grimy layers on cabinets, walls, and ceilings.

2. Types of Ventilation Systems

2.1. Ducted (Extraction) Systems

This is the most effective type of ventilation. It captures the polluted air and expels it to the outside of the building through a duct.

• Components:

  • Hood: The canopy that sits over the cooktop to capture the fumes.
  • Blower/Fan: The motor that powers the suction. It can be located in the hood itself or “in-line” within the ductwork for quieter operation.
  • Ductwork: The pipe that carries the air from the hood to the exterior.
  • Exterior Vent: A cap on the exterior wall or roof that allows the air to exit while preventing pests and weather from entering.

• Suction Power: Measured in Cubic Feet per Minute (CFM) or m³/hr. The required power depends on the type of cooking and the size of the kitchen. A general recommendation is to have a hood that can exchange the total volume of air in the kitchen 15 times per hour.

2.2. Ductless (Recirculation) Systems

Ductless hoods are used when it is not possible to install a duct to the outside. They draw air in, pass it through a series of filters, and then release the “cleaned” air back into the kitchen.

• Filters:

  • Grease Filter: A mesh filter (typically aluminum or stainless steel) that traps larger particles of grease. This is present in both ducted and ductless hoods and needs to be cleaned regularly.
  • Charcoal Filter: The key component of a ductless hood. This filter contains activated carbon that absorbs smoke and odors. It cannot be cleaned and must be replaced periodically (every 3-6 months, depending on usage).

• Effectiveness: Ductless hoods are significantly less effective than ducted systems. They can trap some grease and reduce odors, but they do nothing to remove heat or humidity from the kitchen. They should be considered a compromise solution only when ducting is impossible.

3. Hood Design and Types

• Under-Cabinet Hoods: Compact hoods that are installed under an overhead cabinet.
• Wall-Mounted Chimney Hoods: These have a visible flue that extends up the wall, creating a design feature.
• Island Hoods: Designed to be suspended from the ceiling over a cooktop on a kitchen island. They are generally larger and more powerful to compensate for the lack of a wall to help funnel fumes.
• Downdraft Systems: These are vents that are integrated into the countertop behind or next to the cooktop. They pull air downwards. While they offer a minimalist aesthetic, they are less effective than overhead hoods because they have to fight against the natural tendency of hot air to rise.

4. Ducting Details and Best Practices

The performance of a ducted system is highly dependent on the quality of the ductwork installation.

• Duct Material: Use rigid, smooth-walled metal ducting (aluminum or galvanized steel). Avoid flexible, ribbed ducting, as the ribs create turbulence and reduce airflow efficiency.
• Duct Diameter: The duct diameter should match the outlet on the hood (typically 150mm / 6 inches). Using a smaller diameter will restrict airflow and increase noise.
• Length and Bends: The duct run should be as short and as straight as possible.
  • Rule of Thumb: Each 90-degree bend adds the equivalent of 5-10 feet of straight duct to the total run length, significantly reducing efficiency. Use 45-degree bends where possible instead of 90-degree ones.
• Termination: The duct must terminate at the exterior of the building, not in an attic or wall cavity.

Proper ventilation is a cornerstone of good kitchen design. A ducted system is always the preferred choice for its superior performance in maintaining air quality and protecting the investment made in the kitchen’s finishes.

Building Services · Interior Architecture · Design Studio · Professional Practice · Environmental Design