Extraction and ventilation

Removes the heat, moisture and odour a bar generates continuously, and brings in the air needed to replace what is taken out.

Ventilation is a balance, and the half everybody forgets is the supply half. Air removed from a room has to be replaced, and if no replacement path is designed the room finds one: through the entrance door, which then becomes hard to open and lets in unconditioned outside air at the customer's back; through a gap into a service corridor, dragging its smells the wrong way; or nowhere at all, in which case the extract fan simply stops moving the air its rating claims and everybody concludes the fan is undersized. MAKE-UP AIR IS THE MECHANISM, and it is the reason two identical fans perform completely differently in two rooms. What a bar actually generates is worth separating, because the three loads want different answers. Heat comes off espresso boilers, brewers, hot-water systems, dishwashing and every self-contained refrigeration condenser in the room — refrigeration is the one people leave out, and it is the one that grows through the day. Moisture comes off steaming, hot washing and any open hot water; in a hot humid climate the outside air is already carrying moisture, so the room's dehumidification burden is not a small correction. Odour is generated by waste, by milk, and by anything cooked. And that last category changes the subject entirely: WHERE COOKING OR ANY GREASE-LADEN OR SMOKE-PRODUCING PROCESS IS PRESENT, this stops being comfort ventilation and becomes a specified extract system with fire-safety implications, and the requirement is set by local code and by the fire authority, designed by a mechanical engineer against the actual appliance schedule, and confirmed in writing before installation. This platform states no air-change rate, no extract velocity, no duct size, no canopy dimension and no fan rating. Not because the numbers are unknown, but because the correct ones for a given room are a calculation somebody signs their name to.

• Start from the appliance schedule and the room, and take the answer from a mechanical designer. What is required, whether a canopy is needed at all, and everything about its extent and construction are determined by local code and confirmed by the authority having jurisdiction and the fire authority. This is the item on this page where a confident guess is most expensive.
• State every heat source in the room when the assessment is done, including the ones that are not appliances: self-contained refrigeration condensers, the ice machine, lighting and the people. Refrigeration in particular is left off almost every list, and it is the load that rises as the day and the room warm up.
• Design the make-up air path at the same time as the extract, in the same conversation, and refuse to let it be value-engineered separately. Extract without supply is a fan that does not achieve its rating and a room that solves the problem through your front door.
• Ask what happens in the worst season, not on the commissioning day. A hot, humid outside condition changes both the cooling and the dehumidification burden, and a system signed off in mild weather can be inadequate in a way nobody discovers until the first peak.
• Treat noise as part of the specification, because it is permanent and it sits above the people who work under it. A system that is loud enough to make the team raise their voices for an entire shift will be switched off, and a system that is switched off has no rating at all.
• Confirm the cleaning and maintenance regime before installation, along with the access route for it. Filters, grease-bearing surfaces and ducts all have a required regime, that regime is part of what the authority signs off, and a system nobody can reach is a system nobody cleans.
• Check where the extract discharges and what is near it, because a discharge position is a neighbour question and a licensing question as much as an engineering one. It is a common cause of a complaint that arrives after opening, when it is expensive to answer.
• Get the confirmation in writing and keep it with the commissioning records. Verbal assurance from an installer is not a sign-off, and the person who asks for the paperwork at inspection will not be the person who gave the assurance.