# Make-Up Air for Restaurants, Shops and Commercial Buildings > Make-up air is fresh outdoor air, usually heated, brought in to replace air removed by kitchen hoods and exhaust fans. Without it a building becomes depressurized: doors are hard to open, hoods don't draw and gas appliances can backdraft. Lancaster Heating and Cooling assesses exhaust and ventilation, recommends and installs make-up air, fabricates curbs and ductwork in-house, and maintains and repairs make-up air units across Hamilton and Niagara. Source: https://lancasterheatingandcooling.ca/commercial/make-up-air/ Last updated: 2026-11-02 Every cubic foot of air a kitchen hood or exhaust fan pulls out of a building has to be replaced. If nothing brings it back in, the building goes into negative pressure and pulls air in wherever it can: around doors, through flues and down chimneys. A make-up air unit replaces that air on purpose, filtered and heated, so the exhaust works the way it was designed to and the building stays comfortable and safe. [Ask About Make-Up Air](https://lancasterheatingandcooling.ca/quote/?inquiry=commercial-project) ## Who needs make-up air - **Restaurants and commercial kitchens.** Hoods move large volumes of air. See [HVAC for restaurants](https://lancasterheatingandcooling.ca/commercial/restaurants/). - **Shops, garages and light industrial spaces** with exhaust fans or process exhaust. See [shops, warehouses and light industrial](https://lancasterheatingandcooling.ca/commercial/industrial/). - **Any building where exhaust was added later,** such as a new tenant with a kitchen, a renovation or a change of use, without the supply air to match. ## What we do - **Assess the exhaust and ventilation.** We look at how much air is leaving the building, where it's leaving and what's replacing it, then recommend a solution. - **Install the make-up air.** Sized to match the exhaust, with gas connections made by our licensed gas technicians. As part of [Lancaster Group](https://www.lancastergroup.ca/), the electrical can be coordinated by the same team. - **Fabricate the curbs, transitions and ductwork** in our own [sheet metal shop](https://lancasterheatingandcooling.ca/ductwork/fabrication/), so the unit fits the building. - **Maintain and repair** make-up air units from any manufacturer, 24/7 when something fails. See [commercial HVAC repair](https://lancasterheatingandcooling.ca/commercial/repair/). ## Make-up air and the rest of your HVAC A make-up air unit works alongside the building's heating and cooling, not instead of it. In a restaurant, for example, the rooftop units keep the dining room comfortable while the make-up air replaces what the hood removes. Getting the two to work together matters: too little make-up air and the building goes negative; too much, or air that's too cold, and the kitchen and dining room are uncomfortable. That's why we look at the whole building, not just the hood. See [rooftop units](https://lancasterheatingandcooling.ca/commercial/rooftop-units/). Doors hard to open, or a hood that won't draw? Call **905-388-3333** or [ask about make-up air](https://lancasterheatingandcooling.ca/quote/?inquiry=commercial-project). ## Make-up air questions ### What is make-up air, and does our building need it? Make-up air is fresh outdoor air brought in, and usually heated, to replace air removed by exhaust fans and kitchen hoods. Without it, a building can become depressurized: doors are hard to open, hoods don't draw properly and gas appliances can backdraft. Restaurants and other spaces with large exhaust systems usually need it. We can assess your exhaust and ventilation and recommend a solution. ### What are the signs a building doesn't have enough make-up air? Doors that are hard to open or slam shut, a whistle at doors and windows, a kitchen hood that leaves smoke and odours behind, cold drafts near the entrance in winter, and pilot lights or burners that flicker or go out. Some of these are safety issues: if a gas appliance is backdrafting, combustion gases can spill into the building. Call us and keep carbon monoxide alarms working. ### Why is make-up air heated? In a Hamilton winter, bringing in large volumes of outdoor air without heating it would make the space uncomfortably cold and could freeze pipes or equipment near the intake. Most make-up air units in our climate heat the incoming air, usually with natural gas, to a comfortable supply temperature. ### Can make-up air be added to an existing building? Usually, yes. It depends on how much air is being exhausted, where a unit can go on the roof or wall, and the gas and electrical supply available. Because we fabricate curbs, transitions and ductwork in our own shop, we can fit a unit to an existing building instead of redesigning around off-the-shelf parts. ### Does a make-up air unit need maintenance? Yes. Like any gas-fired heating equipment, it should be checked before the heating season: burners, ignition, safety controls, belts and filters. Filters in kitchens and dusty spaces may need changing more often. We maintain and repair make-up air units from all manufacturers. See [commercial preventive maintenance](https://lancasterheatingandcooling.ca/commercial/maintenance/). --- **Lancaster Heating and Cooling** — HVAC contractor serving Hamilton, Niagara and surrounding areas since 1955. Phone (24/7 emergency): 905-388-3333 · Email: info@lancasterhvac.ca Address: 1250 Stone Church Rd. E, Hamilton, ON L8W 2C8, Canada · Hours: Monday – Friday: 8:00AM – 4:30PM Request a quote: https://lancasterheatingandcooling.ca/quote/