Heating energy, not cooling.

Warm air collects under the roof where nobody is.

The thermostat at head height calls for more.

Mixing the space stops that cycle.

They run hardest in winter.

That makes the business case a heating one.

Larger than most people expect in tall spaces.

It grows with roof height and heat input.

Unmixed warehouses show it most clearly.

Measure floor and roof before assuming.

A cheap logger answers it in a week.

That measurement sizes the scheme.

They drive horizontal bulk movement.

High velocity air induces the surrounding mass to move.

That circulates a whole floorplate without ducts.

Car parks are the familiar application.

They also clear exhaust and assist smoke control.

Ductwork is avoided entirely.

They move far more air than passes through them.

Induction depends on spacing, height and angle.

Wrong placement mixes nothing and makes noise.

Manufacturers model the space to set it.

Ask for the layout, not a unit count.

A quotation without one is a guess.

More than for most fans.

These run continuously in occupied spaces.

A unit chosen on airflow can dominate the room.

Sound power at the working plane is the figure.

Slower larger fans are usually quieter.

Check it against the building's use.

Somewhat, though that is not the case for them.

Air movement improves perceived comfort.

They add no cooling capacity at all.

Some sites run them year round for that reason.

The heating saving remains the justification.

Controls should reflect the seasonal difference.

By temperature difference, ideally.

Sensors at high and low level drive the fans.

They run only when stratification exists.

Running continuously wastes part of the saving.

Simple timeclock control is a poor substitute.

Integrate with the heating controls where possible.