Evaporative Cooling vs Air Conditioning: What Works Best for Warehouses?
September 2, 2025
Air Handling Units (AHU): Installation, Upgrades and Maintenance
September 3, 2025
Commercial HVAC Design for Warehouses: Heat Gain, Ventilation, Ductwork and Plant Rooms
Most commercial buildings do not fail because there is not enough plant, they fail because the HVAC design does not match how the space is used day to day. The strongest projects begin with clear targets, honest calculations of heat gain and fresh air needs, and an airflow plan that fits the work on the floor. From there, plant selection, controls, commissioning and maintenance become straightforward. Based in Preston and working across the UK, Inergy designs and delivers systems around operations first, equipment second.
For more information, please call us on 01204 929 999. Free consultation and site visit, as required.
Quick answer: how to design an HVAC system for a commercial building
Define the temperature, humidity, air quality and noise targets for each zone. Survey the building fabric and usage. Work out heat gain and fresh air requirements with transparent inputs. Choose the right strategy by zone. Size airflow and ductwork to reach people at work height. Select plant and diffusers to match the duty. Keep controls simple with the right sensors. Commission against the brief and plan seasonal maintenance from day one.
Why warehouses need a different design to offices or factories
Warehouses are tall and busy. Doors open often, air volume is huge, and heat sources move. Air conditioning struggles in that setting because losses are high and air tends to stratify. Offices are sealed and quiet, so comfort depends on steady temperature, fresh air and low noise. Factories add process heat, fumes and local extraction. Good commercial HVAC design respects these differences. It applies the right method to each area instead of forcing one solution across the estate.
Fundamentals of HVAC design that keep projects on track
Start with outcomes, not kit. Agree temperature bands by area and time. Confirm humidity limits if stock or processes are moisture sensitive. Set indoor air quality targets that make sense for the activity. Capture operating patterns, door cycles, shift lengths and headcounts. Put all this into a short written brief. A clear brief is the anchor through design, procurement and commissioning.
Survey the building fabric and how people actually use it
Measure clear heights, racking, mezzanines, heat sources and glazing. Check the roof structure for plant weights and safe access. Map air paths and pressure relief openings. Note solar gains and wind exposure. Walk the floor during a shift and watch how people move and where they stand for hours. This reveals hot spots, draughts and pinch points that drawings never show.
Heat and fresh air calculations you can defend to anyone
Use transparent inputs. External heat gain through walls and roof. Solar through glazing. Internal heat from people, lighting, motors and processes. Fresh air for people and any process exhaust volumes that match the activity. Apply diversity and coincidence factors that reflect how demands line up in time. For open warehouse cooling, be realistic about leakage and door openings. If the strategy uses high airflow with outside air, base the design on achievable supply air temperatures in UK summer and on the air volume required to sweep heat out of work zones.
Airflow and ductwork design that prevents hot spots
Treat airflow as the first problem to solve. Get cool air to where people stand and give it a simple route out of the building.
Typical design velocities. Use 4 to 7 m per second for supply mains in commercial ductwork. Use 3 to 5 m per second for branches in offices. In high bays, reduce velocities to keep noise down and throw long. Keep runs short and straight. Use large radius bends and minimal flexible sections. Balance branches at zone entries with volume control dampers. In tall warehouses, fabric ducting or long throw nozzles give even spread at worker height without wasting air in the roof void. These are the essentials of sound HVAC ductwork design.
Choosing the right strategy by zone
Warehouse floor. Open volume, high doors, moving targets. A high fresh air strategy with large supply volumes and simple relief paths fits best. In many UK warehouses, evaporative cooling provides the lowest running cost and the most even comfort because it brings in cool, fresh air and pushes warm air out.
Offices and enclosed rooms. Use air conditioning with defined fresh air and steady setpoints. VRF and packaged systems are common. Keep noise low and airflow gentle near desks and meeting rooms.
Workshops and production lines. Mix source capture near hot machines with general supply air. If fumes or dust are present, design extraction at source and keep the rest of the space slightly positive with clean supply.
When a zone is open and high, refrigerating the entire volume is rarely the best path. When a zone is sealed and small, close control from mechanical refrigeration makes sense. The right commercial HVAC design usually combines both in a simple hybrid.
Plant selection and diffuser strategy that matches the duty
Evaporative units. Select by duty airflow, pad area and fan pressure at the operating point. Place units to sweep across work zones rather than up into the roof. Provide relief openings near the high side of the space and use door positions to pull warm air out. For a deeper method article, see our detailed guide to HVAC design for evaporative cooling.
Air conditioning. Select to meet the temperature and moisture control required, with allowance for ventilation and distribution effects. Keep external static pressures reasonable. Make space for service access and coil pulls. In offices, choose diffusers that avoid draughts at head height and keep background noise low.
Ventilation. For processes, design local extraction sized for capture rather than brute force dilution. Run short ducts to atmosphere. Then backfill the space with clean supply so doors and cracks are not the only air path.
Controls and sensors that people understand
Keep controls simple. Put temperature sensors at worker height and where people actually stand, not in the roof void. Add door status inputs so the system adapts when shutters are open. Use seasonal setpoint schedules. Interlock supply and exhaust so building pressure stays near neutral. Meter energy and key temperatures so you can measure performance and tune settings with evidence.
Evaporative Cooling Design Checklist
Every building is different. This checklist takes a project from first visit to sign-off with clear, practical steps.
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Site survey
Walk the space during live operations. Record the layout, door cycles, racking, heat sources and any existing ventilation. Confirm safe plant locations, roof access, water quality, drainage, and electrical capacity. -
Concept and system selection
Choose the approach that fits the space: roof, wall or mixed supply with simple relief paths. Pre-size duty airflow, pad area, unit quantity and placement. Shortlist proven equipment such as Breezair or Climate Wizard to meet duty, noise and maintenance needs. -
Performance modelling
Estimate expected supply temperatures in typical UK summer conditions. Forecast air movement across working zones and the air change rate in those zones. Produce annual electricity and water use estimates with running cost and CO₂ comparisons. Prepare notes for Building Regulations and health and safety compliance. -
Detailed design
Produce CAD layouts and sections showing unit positions, penetrations and safe access. Schedule ductwork or distribution, diffusers, controls and sensor locations. Specify water treatment, isolation valves, drains and maintenance clearances. -
Installation planning
Create a programme that avoids peak trading hours. Plan cranage and access, lifting routes, permits and method statements. Confirm power and water connections, protection, and any temporary works. -
Commissioning and handover
Test and balance airflows, verify temperature drop and prove relief paths with doors operating. Set controls and alarms, then train the facilities team. Provide O&M documents, spares lists and a simple maintenance plan. Include a post-installation performance check after the first warm spell to fine-tune settings.
Commissioning and handover that holds under real use
Commissioning is not a paperwork exercise. Test airflows and balance in the zones where people stand. Prove controls with real door cycles. Set alarms that make sense. Provide a short manual with part numbers, service intervals and contact details. Book a seasonal visit before summer so the system is ready when heat arrives.
Maintenance that protects performance for years
Design for maintenance from the start. Provide clear access to filters, pads and strainers. Fit isolation valves and drains where needed. Keep spares for pumps, belts and critical sensors. If you run both cooling and heating, define a crossover temperature and simple rules so the systems are not fighting. A realistic plan prevents small faults from becoming expensive failures.
Energy and sustainability choices that lower bills without lowering comfort
The fastest way to cut running cost is to avoid removing heat you do not need to remove. Reduce gains where practical, then choose systems with low electrical input per unit of cooling. In tall, open volumes, high airflow fresh air strategies often give the lowest kilowatt hours and the best indoor air quality because they use water and fans rather than refrigerants. Pair that with efficient fans, sensible controls and building improvements and you have a strong path toward your carbon plan. If you need help beyond design, our HVAC services cover survey, project delivery and maintenance with a single point of accountability.
Worked example 1. Open warehouse picking zone
Assumptions. Floor 3,000 square metres at 8 metres height. Active picking in 1,800 square metres. Summer outside 28 Celsius and 50 percent relative humidity. Target worker zone 23 to 26 Celsius with air movement. Two roller doors that cycle frequently. People density varies by shift.
Approach. Select evaporative units for 8 to 10 air changes per hour across the active zone. Use roof units with distribution that throws along aisles and drops at worker height. Keep relief paths simple with eaves vents and door openings. Offices off the warehouse run on VRF with defined fresh air. Controls tie supply volume to door status and temperature.
Outcome. Supply air typically 18 to 22 Celsius in UK summer. Perceived floor temperature 6 to 10 Celsius below outside. Electrical input a fraction of an equivalent AC design over the same area. Complaints about hot aisles drop and picking rates stabilise through the afternoon.
Worked example 2. Mixed office and production floor
Assumptions. Production hot spots, light solvent extraction, 1,200 square metres of office space on two floors.
Approach. Use targeted extraction near hot processes sized for capture velocity. Provide make up air from a central supply so the general space stays slightly positive. Offices run on VRF with 8 to 12 litres per second per person fresh air and heat recovery where duct routes are practical. Controls allow night purge and reduced setpoints outside occupied hours.
Outcome. Odours are contained at source, offices stay quiet and comfortable, and energy use is far lower than a single big recirculating system.
Worked example 3. Small clean area inside a warehouse
Assumptions. Pack room clean area for product finishing. One transfer lobby. Staff gown inside the clean area. Tight temperature and particle targets.
Approach. Create a simple pressure cascade so air always flows from clean to less clean. Use high efficiency filtration on supply. Put return air low level to sweep particles out of the working zone. Interlock doors so pressure stays stable when people move. Use a dedicated air handling unit with sensible cooling and tight control of temperature and humidity. Train staff on entry routines since behaviour is part of clean room performance.
Outcome. The pack room meets cleanliness targets, comfort stays steady, and the rest of the warehouse continues to use low energy cooling.
Clean room HVAC design in commercial settings
Some commercial sites run clean areas for packaging, assembly or lab work. Clean rooms need controlled particle counts, pressure and temperature. Pressure differentials are small yet constant so air always moves from clean to less clean spaces. Filtration is high efficiency and air changes can be high compared to general areas. Clean room HVAC design calculations focus on supply volumes for particle control, filter face velocities that protect media life, return and extract locations that sweep contaminants, and pressure control that is stable when doors open. Most failures come from vague user requirements. Agree cleanliness class, pressure cascade and acceptable temperature and humidity bands before you size anything.
Data rooms and data centres cooling inside a commercial estate
Data rooms add dense, steady heat and strict uptime requirements. Aisle containment, short air paths and high reliability matter more than a single efficiency number. Many estates separate the data room into its own zone with dedicated cooling, humidity control and monitoring, while the rest of the building follows standard commercial HVAC design. In small server rooms inside warehouses, protect against recirculation, keep cable penetrations sealed and design make up air and relief so pressure does not disturb door operation. For wider options and methods, see our approach to data centres cooling.
Plant room design that works on day one
A well planned plant room saves hours during install and years during maintenance. Provide walk around access to all faces of large equipment. Keep clearances for coil pulls and pump changes. Group isolation valves and strainers where they can be reached. Provide safe drainage for blowdown and cleaning. Ventilate the room to remove residual heat and think about noise to adjacent spaces. Firestopping, penetrations and cable trays should be coordinated before the first fix so late changes do not break the programme. These are the essentials of robust HVAC plant room design.
Designing offices inside warehouses without constant complaints
Treat internal offices as separate zones. Use VRF or packaged units sized to the people requirement with defined fresh air and heat recovery where it fits. Control noise, especially near meeting rooms and quiet spaces. Route refrigerant lines and drains with easy access for service. Insulate partitions properly so office comfort is not at the mercy of warehouse temperature.
Commercial HVAC design procurement that keeps you in control
Write a short technical brief that vendors must follow. State indoor targets by zone, design conditions and what must be included in commissioning. Ask bidders to show their temperature, humidity, fresh air and exhaust calculations, airflow rates, fan curves, noise data and service clearances. Favour suppliers who explain trade offs rather than promising the same outcome everywhere. Ask for a simple maintenance plan and real parts availability. Independent selection against your site’s heat gains, airflow needs, layout and lifecycle costs is the best defence against oversizing and overspending.
What commercial HVAC design looks like as a simple workflow
- Define targets and constraints.
- Survey the building fabric and usage.
- Work out heat gain, fresh air and moisture needs with transparent inputs.
- Choose the strategy by zone.
- Size airflow and lay out ductwork or plenums.
- Select plant and diffusers.
- Set controls and sensors with simple logic.
- Commission and balance with the brief in hand.
- Plan maintenance before the first warm day.
Common mistakes and how to avoid them
Oversizing to feel safe. Big systems short cycle, waste money and still miss comfort. Use realistic diversity and prove it.
No clear relief path. Supply air with nowhere to go creates pressure problems and hot corners. Draw the path out of the building.
Sensors in the wrong place! Roof void sensors do not protect people on the floor. Put sensors at worker height.
Trying to refrigerate open volumes. Use high airflow strategies where doors open often and ceiling height is large.
Complex controls for simple buildings. Keep logic readable and maintainable.
For more information, please call us on 01204 929 999. Free consultation and site visit, as required. Or click here to contact us.
FAQ
What is HVAC system design in a commercial building
It is the process of defining indoor targets, working out heat gain and fresh air needs, choosing a strategy by zone, sizing airflow and ductwork, selecting plant and diffusers, commissioning and planning maintenance. It is not a product choice first, it is outcomes first.
Which software is used for HVAC design
Use building heat gain tools for envelope and internal gains, airflow calculators for velocities and pressure drops, and CAD or BIM for coordination. You do not need exotic software to get reliable answers, you do need transparent methods.
How should I approach HVAC ductwork design
Set design velocities, balance branches, keep runs short and straight and use distribution that reaches people at work height. Avoid dumping air into the roof void. Fabric ducts and long throw nozzles can give even spread across long aisles.
How do I handle clean room HVAC design calculations
Begin with a clear user requirement. Define cleanliness class, pressure cascade, temperature and humidity bands. Calculate supply volumes for particle control, plan return locations for sweep and size filters with realistic loading. Keep door pressure stable with sensible control.
Who should I speak to for commercial HVAC design help
Choose independent designers who will commit to a brief and explain trade offs. We provide advice, design and delivery under one roof so you choose the method that suits your building, not a single product line.
Next steps
Every site is different. The best scheme for one warehouse is not always the best scheme for the next. If you want a recommendation that matches your building and your operation, get a survey, a transparent set of heat gain and fresh air figures, and an airflow plan that you can review easily. We keep the method clear so you can challenge the numbers with confidence. Contact us for a free consultation and site survey. If you prefer to start with a call, 01204 929999 connects you with a designer who will ask about the space, the shifts and the outcomes you need.
