HVAC for Warehouse Ventilation: Air Changes, Evaporative Cooling and When AC Is Needed

Most dry-goods warehouses need ventilation, not air conditioning. NBC 2016 lists 3 to 6 air changes per hour for stores and warehouses, which roof fans and louvres can deliver. Evaporative cooling helps in hot, dry months but stalls in humid weather. Conditioned air is justified only when the stock itself needs a set temperature or humidity, as pharma, electronics and some foods do.

How many air changes per hour does a warehouse need?

The National Building Code of India 2016 (Part 8, Building Services) carries a table of recommended ventilation rates in air changes per hour (ACH). CSIR reproduces that table in its ventilation guidelines, hosted by NITI Aayog, and it lists stores and warehouses at 3 to 6 ACH. The same table gives paint shops (not cellulose) 10 to 20 ACH and underground vehicle parking at a minimum of 6. Read the table in the code itself before you freeze a design, because the document we used is a reproduction.

The arithmetic is simple. Airflow in cubic metres per hour is the volume of the space multiplied by the ACH. A shed holding 20,000 cubic metres at 4 ACH needs 80,000 cubic metres per hour, about 22 cubic metres per second. That figure is the total across all fans, and it must be matched by an equal inflow through wall louvres, doors or dedicated intake openings. A fan that has no air path to draw from moves very little. Our ventilation calculator runs the same sum and shows the fan count for a given duty.

Two practical points move the number. Heat from the roof loads the space in summer, so a bare metal roof usually needs more air than an insulated one for the same temperature rise. Occupied zones, such as packing tables and dispatch bays, may deserve a higher local rate than the open racking aisles.

Which storage type decides the cooling design?

The stock decides the design before the climate does. Ask what the product label, the customer or the licence says about storage temperature and humidity. If the answer is "ambient", ventilation is enough. If it is a range, you are designing a controlled space, and that changes the equipment, the envelope and the electrical load.

For battery charging rooms and paint booths we have a separate note on ventilation for charging rooms and paint booths.

When does evaporative cooling work in a warehouse?

Evaporative cooling passes air through a wet pad and lowers its temperature by evaporating water. The India Cooling Action Plan (Ozone Cell, MoEFCC) states that the cooling effectiveness of air coolers is constrained by the humidity of the ambient air, so performance varies a great deal between hot-dry and composite climates on one side and warm-humid climates on the other, and between seasons. It adds that coolers need adequate ventilation to work in humid conditions. It also notes that cooling pad efficiency depends on the pad, with aspen pads about 75 percent and honeycomb about 85 percent efficient.

For a warehouse this means three things. First, it is a once-through system: the cooled, moister air must leave through relief openings, so the building needs an exhaust path as large as the supply. Second, the supply air is humid, so it suits stock that tolerates humidity and not cartons, electronics or bright metal. Third, it uses water, and the pads and water treatment need maintenance. In north India, an evaporative system can be useful from April to June and is much weaker in July to September. Treat any promise of a fixed supply temperature with caution until the wet-bulb design condition for your site is on the drawing.

When is air conditioning justified, and what drives its cost?

Air conditioning is justified when stock value, product stability or a customer audit depends on holding a range. The sensible move is to condition only the zone that needs it. A 2,000 square metre enclosed room inside a large shed costs far less to run than conditioning the whole building.

Cost drivers, in the order they usually matter:

• The envelope: insulated roof and wall panels, sealed joints, and the number and size of dock doors that open to the outside.
• Setpoint and hours: a ceiling of 30 degrees and a band of 20 to 25 degrees are different machines.
• Equipment type: packaged units, VRF or a chilled-water plant, chosen by load and by the distance between the plant and the space.
• Air distribution: tall sheds stratify, so supply throw and return position matter more than tonnage.
• The electrical connection: a conditioned zone adds a continuous load, so check the transformer, the cable and the demand charge before you buy the equipment.

A conditioned warehouse also adds a daytime base load that a rooftop solar plant can offset; see our note on solar for factories. Size the cooling load with the AC tonnage calculator only after the envelope is fixed.

What do ventilation and fire design need to agree on?

Ventilation openings, roof vents and exhaust fans interact with the fire design: sprinkler response, smoke movement and the interlocks that stop fans on a fire alarm. The fire design and the local fire officer decide the interlocks, so put the ventilation layout in front of the fire designer before it is fixed. Our own ventilation, pressurisation and exhaust service is designed alongside the fire layout for that reason.

How Secured Engineers helps

We design the ventilation and cooling in-house, with the electrical and fire design on the same drawings, so the fan load, the cable and the sprinkler layout are checked against each other. Fire NOC, CEIG and DISCOM net-metering filings are done in-house. MEPF and solar can sit under one contract. We work from our Noida (Delhi NCR) and Ludhiana offices, across 535+ projects in 18+ states, and 89.77% of our clients return.

If you have a layout, a storage list and a door schedule, send them for a file review. We will say whether ventilation is enough, which zone justifies conditioning, and what the electrical connection must carry. Start with the ventilation service page, message us on WhatsApp, call +91 70099 85817, or ask for a free proposal.