Cold Workshop When Exhaust Fans Run Understanding Make Up Air

Why does your warehouse or workshop become colder when the exhaust system starts? Exhausted air needs replacement air. If that air enters through uncontrolled paths or is not conditioned appropriately for the application, drafts and heating complaints can follow. A review of exhaust, make-up air and space heating together can help establish the cause without compromising the ventilation needed for the work.

For an industrial operator, the timing of the complaint is valuable. A building that feels acceptable before production but becomes uncomfortable during extraction may need more than a larger space heater.

Winter makes the relationship easier to notice because replacement air can arrive much colder than the occupied space. However, comfort is only one consideration. Ventilation may also serve a process or exposure-control function, so adjustments need to preserve that purpose.

What make-up air means

Make-up air is air supplied to replace air removed from a space. It can be introduced through a designed supply arrangement rather than relying on leaks and open doors to provide the replacement.

The Canadian Centre for Occupational Health and Safety explains the relationship between supply and exhaust in its industrial ventilation introduction. Its guidance is a useful starting point for understanding why these systems need to be considered together.

A make-up air unit may filter and condition incoming air as part of the installation. The exact functions depend on the equipment and design. Do not assume that every unit heats, cools or controls humidity in the same way.

Reliable Mechanical's make-up air services are relevant when a facility needs to discuss replacement-air performance or a change in operational needs.

Document which fans and processes are operating

Begin by describing the normal working day. Identify which extraction systems run continuously, which start with production and which operate only during particular tasks. Include overlapping operation rather than looking at each fan separately.

Record when complaints begin and whether they stop when the operating pattern changes. A note that the packing area becomes drafty whenever two processes operate together may be more useful than a general statement that the warehouse is cold.

Include recent additions. A new extractor or an extended production shift can change air requirements even if the space-heating equipment remains unchanged.

Avoid assuming a connection simply because two events occur together. The observations guide the assessment; measurements and system review establish the cause. A clear timeline helps the technician choose the conditions that need to be evaluated.

Identify where replacement air is entering

Tell the service team where staff feel drafts and whether doors have become difficult to use. Include observations around loading bays, corridors and adjacent offices. These are clues rather than a complete pressure diagnosis.

Door operation, weather and other building systems can influence the conditions. Measurements should be interpreted with that context, particularly in a facility with multiple connected spaces.

Do not use an open exterior door as the permanent answer to an air-supply problem. It may alter comfort and airflow without demonstrating that the process receives the air arrangement it requires.

Similarly, do not block a supply opening because the air feels cold at a nearby workstation. Report the issue so that air temperature, distribution and system operation can be considered together.

Check the relationship with space heating

A warehouse heater and a make-up air system have different roles. The space heater may be selected to maintain room conditions, while the replacement-air system deals with the air required by exhaust operation.

If incoming air is colder or more abundant than the heating design assumed, the room's conditions may change. That does not establish which component is at fault; it shows why the system needs a coordinated review.

Ask whether the assessment includes the normal exhaust rate, supply conditions and heating requirements. A quotation for a larger heater should explain the assumptions used and whether other air-system issues remain.

Reliable Mechanical's commercial HVAC services can support a discussion that includes both heating and ventilation. Describe the operational problem rather than requesting a particular piece of equipment before the investigation.

Review the supply-air path

Air needs to reach the intended areas through a suitable arrangement. Changes to racks, partitions or equipment can alter where a supply stream travels. Staff may experience a cold draft even when the overall system appears to be running.

Review the current floor layout with the contractor. Mark occupied workstations, process equipment and storage that has been added since the ventilation arrangement was established.

Do not redirect industrial supply air without considering how it interacts with extraction and the worker's position. A change that improves comfort locally could disturb the intended movement of contaminants.

The appropriate assessment should connect the process requirements with the proposed air distribution. It may require ventilation design expertise beyond a routine mechanical service visit. Clarify who is responsible for that part of the work.

Consider condition and maintenance

Equipment that receives a run command may not be delivering its intended performance. Fans, filters, controls and other components need to be assessed according to the installed system and manufacturer requirements.

Ask whether the inspection can establish the actual operating condition rather than simply confirming that a fan motor starts. The useful question is whether the arrangement performs its required function under normal production conditions.

The CCOHS guidance on industrial ventilation installation and maintenance highlights the importance of maintaining both supply and exhaust systems. Use equipment-specific instructions to determine the actual service tasks and intervals.

Keep records of findings and approved changes. If a problem returns after filter replacement or another intervention, the service history helps the next technician understand what improved and how long the improvement lasted.

Do not solve drafts by weakening extraction

An exhaust system may exist to remove material generated by a process. Turning it down to reduce heating demand can change its ability to serve that purpose.

Ask for the extraction requirement to be established by the appropriate qualified team. Comfort improvements should then be designed around preserving the necessary function.

This applies to controls as well. An interlock or operating sequence should not be bypassed because it makes startup inconvenient. Report the problem and have the intended operation reviewed.

A ventilation improvement needs a clearly defined outcome: the process remains appropriately served and occupied areas receive suitable conditions. A warmer room alone does not demonstrate that an industrial ventilation project has succeeded.

Plan for production changes before installation

When adding a process, involve the mechanical and ventilation team before equipment locations are fixed. Provide the process supplier's requirements, intended hours and expected overlap with existing operations.

The review should identify the effect on replacement air, heating and related utilities. It should also consider where equipment can be installed and how it will be accessed for future maintenance.

Ask who owns the complete design. Several suppliers may each provide a component without taking responsibility for how the components operate together. Clarify the interfaces before accepting the project scope.

If the installation is phased, define the acceptable interim operation. The facility should not rely on a future make-up air project to compensate for an exhaust change that has already been placed into service without appropriate review.

Compare proposals using the same operating description

Provide each bidder with a consistent description of the process, schedules and required outcome. Otherwise, one proposal may assume intermittent extraction while another assumes continuous simultaneous operation.

Ask what is included in controls, connections, air distribution and commissioning. Identify any design work or building modifications that are excluded so the owner can see the complete project responsibility.

Discuss access and service clearances before choosing a location. An installation that is difficult to reach may become difficult to maintain, even if it fits neatly into the available space.

For any projected energy savings, request the baseline and assumptions. The business case should preserve required ventilation and reflect the actual operating schedule. A generic percentage from another building is not a forecast for your workshop.

A practical winter investigation

Consider a hypothetical facility where drafts appear at an assembly bench after a second exhaust process is introduced. The owner initially considers adding another suspended heater.

A useful assessment would document the two process schedules, review the replacement-air arrangement and measure conditions during representative operation. It would also consider the bench location and changes in air distribution.

Possible outcomes could include servicing equipment, revising an appropriate control sequence or planning a designed air-supply improvement. The symptoms alone cannot establish which option is correct.

The important result is an explanation that connects the recommended work to the observed conditions. That allows the owner to understand why the intervention is needed and what performance should be checked when the work is complete.

Make the handover useful

At completion, request a description of the intended operating sequence and the conditions used for verification. Retain the relevant measurements, settings and outstanding items with the system records.

Explain approved controls to the people who start and stop production. A system can be correctly installed but operated differently if its sequence is not understood by the shift team.

Plan a follow-up if the work could not be evaluated during normal production or representative winter weather. Identify what needs review rather than leaving an open-ended promise that someone will return if required.

Finally, connect the system to an appropriate maintenance plan. Supply and exhaust performance should remain visible in the building's records as processes and schedules evolve.

Frequently asked questions

Is make-up air the same as recirculated heating air?

No. Make-up air replaces air exhausted from a space. A space-heating system may recirculate indoor air. The functions and the amount of outdoor air involved need to be identified for the actual installation.

Will a bigger warehouse heater solve cold drafts?

It may not. The source, amount and distribution of replacement air should be assessed alongside heating performance. Increasing heat output without understanding the airflow may leave the underlying problem unresolved.

Can we reduce exhaust operation in winter?

Only make changes following an appropriate review of the process and ventilation requirements. Do not reduce a system's protective function simply to improve comfort or reduce heating costs.

When should a facility review its make-up air?

Review it when extraction changes, production expands, layouts change or repeated complaints appear during system operation. Providing information early can help integrate the mechanical work into the project.

Discuss winter air replacement with Reliable Mechanical

If your Brampton, Bolton or GTA facility experiences cold drafts when exhaust systems run, begin with the operating pattern and the current air-supply arrangement. A coordinated review can identify the next step more effectively than choosing a heater in isolation.

Contact Reliable Mechanical or call 905-457-2665 to discuss make-up air, ventilation and the heating needs of your operation.