Factory HVAC: conditioning for the product or for the people

Two clients making claims on the same air

Materials warp, absorb moisture, cure at different rates, or fail to bond outside a defined range. Adhesives, coatings, powders, paper, timber, textiles and electronics assembly all have conditions they need. People need something different and have a legal entitlement to a reasonable working environment regardless of what the process prefers. When the two conflict, the resolution is usually zoning rather than compromise, since conditioning a whole hall to satisfy the most demanding operation is expensive and often still fails to satisfy it. Establishing both requirements separately, in writing, is the step most projects skip.

Humidity is the requirement nobody states

Temperature gets specified because everyone understands it. Moisture content gets omitted, and then causes the problems that take months to diagnose: dimensional change in hygroscopic material, condensation on cold surfaces or incoming stock, static in dry conditions, corrosion, coatings that will not cure. Controlling humidity is a substantially different engineering problem from controlling temperature and can dominate the plant design and its running cost. If the product has any moisture sensitivity, state it as a requirement at the outset, because adding humidity control to a system designed only for temperature is close to starting again.

Zoning beats conditioning the whole volume

Production halls are large, tall and full of doors, which makes them expensive spaces to hold at a condition. Where only one operation needs control, enclosing that operation and conditioning the enclosure is almost always cheaper to build and to run than treating the entire building. The same reasoning applies to heating people rather than volumes: locally directed heating at fixed workstations can serve better than raising the temperature of air that spends its time near the roof. Zoning does add complexity in control and in maintaining boundaries between areas, which needs designing rather than assuming.

Internal heat gains change the whole calculation

A factory generates its own heat. Motors, ovens, furnaces, hydraulics, compressors, lighting and people all contribute, and in many plants the summer problem is not warming the building but removing what the process produces. Any conditioning design that ignores internal gains will be wrong in both directions: oversized for heating, undersized for cooling. This is also where the interaction with process cooling matters, since heat rejected from equipment into the hall becomes a load on the air handling. Provide the designer with a realistic picture of installed equipment and operating patterns, not a nominal list.

Specification, installation and commissioning are engineering work

Load calculation, plant selection, air distribution, control strategy and the interaction with ventilation and fire systems are the responsibility of mechanical services engineers working to the codes applying at the site. What the occupier contributes is the requirement: what the product needs, what the process emits, how the space is used, and what the tolerance for failure is. Insist that achieved performance is measured and recorded at handover against those requirements. Systems accepted without commissioning evidence tend to be discovered as inadequate during the first extreme weather, when nobody can establish what was promised.

Frequently asked questions

Does a factory have to be heated to a particular temperature?

Workplace regulations in most jurisdictions require a reasonable temperature in indoor workplaces and set expectations rather than a single universal figure, with allowances for processes that make close control impractical. Where the process prevents comfortable conditions, the duty usually shifts to providing other measures such as local heating, protective clothing, rest facilities or work rotation. Check what applies at your location and record how the requirement is being met, because this is a routinely inspected area and an obvious source of workforce complaints.

How do we decide between conditioning the whole hall and enclosing one area?

Compare the capital and running cost of each against the area that genuinely needs control. If a small proportion of operations drive the requirement, an enclosure is usually far cheaper on both counts and gives tighter control than a large space can achieve. Whole-hall conditioning makes sense when most operations need it, when material moves continuously between areas, or when the product cannot tolerate the transitions involved in entering and leaving a controlled zone.

Why do conditions vary so much across our production area?

Large halls stratify, with warm air collecting high and cold air pooling at floor level and near doors. Add localised heat from equipment, cold draughts from dock doors and extraction pulling air through the building, and conditions can differ considerably between two points that look similar. Measuring at several positions and heights over a period, rather than at one thermostat, usually explains complaints that seem contradictory and points to whether the answer is destratification, sealing, replacement air or zoning.