GB-GAS Ventilation Calculator

Select a calculator

Choose the appliance or ventilation calculation required.

www.gb-gas.co.uk

Appliance details

Heat inputkW

Ventilation requirements

Appliance in a room

Direct to outside0.00 cm²

Appliance in a compartment

Direct outside — top vent0.00 cm²

Direct outside — bottom vent0.00 cm²

Via room — top vent0.00 cm²

Via room — bottom vent0.00 cm²

Room to outside0.00 cm²

Appliance details

Heat inputkW

Compartment ventilation

Direct outside — top vent0.00 cm²

Direct outside — bottom vent0.00 cm²

Via room — top vent0.00 cm²

Via room — bottom vent0.00 cm²

Room dimensions

Enter dimensions in metres.

Lengthm Widthm Heightm

Room volume

Calculated volume0.00 m³

Cookers

Enter the room dimensions to display guidance.

Water heaters

Enter the room dimensions to display guidance.

For flueless gas fires and space heaters, always use the manufacturer’s instructions.

Vent requirements

Enter each appliance’s normal ventilation requirement in cm². Space heating is for heating the house, Boilers, Warm Air, Fires etc.

Open-flued space heating appliances

Open flued 1cm² Open flued 2cm² Open flued 3cm²

Flueless space heating appliances

Flueless 1cm² Flueless 2cm²

Largest vent size of any other appliance

Largestcm²

Vent required

Vent to fit0.00 cm²

Ventilation path

Enter the appliance’s normal direct-to-outside vent size.

Outside vent sizecm² Appliance is in a compartment Ventilation path is through more than two rooms

Vent sizes

Compartment high-level ventN/A

Compartment low-level ventN/A

Intermediate room vent(s)0.00 cm²

Vent to outside0.00 cm²

Rectangular holes

Enter length, width and number of holes in millimetres for up to three different sizes.

LengthWidthNumber

Free area0.00 cm²

Circular holes

Enter diameter in millimetres and number of holes.

Hole diametermm Number of holes

Free area0.00 cm²

Definitions and guidance

Open-flued appliances

Includes appliances that take combustion air from the area in which they are installed and discharge products of combustion through a flue to outside.

Room-sealed appliances

Includes appliances with a two-part flue arrangement: one path for combustion products and another for combustion air. This includes fan-draught and natural-draught appliances.

Gross and net

The original app uses a gross-to-net conversion factor of 1.1.

Flueless appliances

Includes appliances that take combustion air from the installation area and discharge products of combustion into the same area.

Important: Check and comply with the appliance manufacturer’s instructions, particularly for modern flueless gas fires where minimum room volume is critical.

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