Warehouses tend to squeeze the most out of their HVAC systems. Long hours, mixed-use zones, open roller doors, racking that never quite stays the same for long. When a TM44 inspection lands, it often exposes patterns that facilities teams already suspect: drifting controls, equipment past its best, and airflow that never lined up with the floorplan. The difference is that a TM44 report translates those suspicions into actionable findings, tied to energy waste, comfort risks, and compliance. Over the years, I have walked through chilled cross-docks, high-bay ambient stores, and everything in between, and similar issues usually recur. The shape of the building changes, the acronyms change, but the energy profile follows a familiar arc.
This piece unpacks the most common TM44 findings in warehouses and explains, in practical terms, what to do next. No silver bullets, just well-tested fixes and the trade-offs that come with them.
How TM44 fits into warehouse reality
TM44 guidance covers the inspection of air conditioning systems above 12 kW, focusing on efficiency, condition, and controls. For warehouses, that usually means a mix of split systems in offices and welfare rooms, packaged units on mezzanine offices, and, in larger facilities, air handling units (AHUs) or rooftop units serving bigger conditioned zones like pick areas or clean rooms. Cooling is often seasonal, but ventilation runs most of the year. Heating is sometimes separate, handled by gas-fired radiant tubes or direct-fired make-up air units. Inspectors look across this whole picture, even if portions sit outside classic “air conditioning.”
The warehouse environment complicates the basics. Doors open for most of the shift. Load profiles change during peak season. Pallet racking creates microclimates and stagnant pockets. Mechanical systems that made sense at practical completion no longer fit the operating pattern a few years later. TM44 picks up on those mismatches and the energy drift they cause.
Controls that fight the building
The most common TM44 finding across warehouses involves setpoints and schedules. Two adjacent systems with different objectives wind up working at cross purposes. A typical example: a mezzanine office cooled to 21°C while the open warehouse beneath is warmed by radiant tubes to 18°C. The staircase acts as a flue, dragging heat upwards, so the office units run hard even when unoccupied. Another frequent error is fan-only modes running overnight with doors and vents open, effectively pulling cold night air across coil banks and wasting energy in standby.
The quickest win often comes from revisiting the control strategy with a short list of questions. Which zones truly need cooling year-round? Are there shift patterns that allow setback temperatures for two thirds of the day? If radiant heat is used, can office walls be better sealed or staircases fitted with simple, code-compliant doors to slow convective flow? Where a BMS exists, alarms on simultaneous heating and cooling can surface the worst clashes. In smaller sites without central controls, training the onsite team to calibrate setpoints each season pays off. A two-degree widening of a deadband can cut compressor starts significantly, and that is a real number you will see on the monthly kWh chart.
A detail that too often gets missed: occupancy sensors tied to ventilation and cooling in small office pods. Inspectors frequently note systems idling into the night because a manual override was left on for a Friday overtime shift. Linking time clocks to access control, or at least to a central weekly schedule, reduces these slip-ups without policing behavior.
Sensor placement that misreads reality
Even good controls fail when sensors sit in the wrong place. In high-bay storage, warm air stratifies above nine meters while the occupied zone can swing with door openings and forklift traffic. I have seen return-air sensors mounted near ceiling level or behind process heat sources. The system thinks the space is hot, so it drives cooling that never reaches people on the floor. TM44 inspectors flag this when they find persistent setpoint offsets or when temperature logs show wild variation.
The fix starts with relocating sensors to representative spots in the occupied zone. In very tall spaces, destratification fans help homogenize air, but they need to be commissioned against real conditions, not a spec sheet. A simple, low-cost tactic is to log temperatures at a few key points for a week. The data usually shows two or three predictable problem windows, often aligned with morning deliveries and late afternoon solar gain along the south wall. With those patterns mapped, you can move sensors and adjust fan speeds to track the real load. If sensors cannot be moved, weighted averaging across multiple points is better than a single, unrepresentative reading.
Maintenance gaps that look small but cost big
TM44 puts weight on maintenance records, and for good reason. The most energy-intensive faults are the boring ones: fouled condenser coils, blocked return grilles pinned behind pallets, and tired fan belts. A warehouse can accumulate dust quickly. Add cardboard fiber and diesel particulate near loading bays, and condenser efficiency can plunge within a season. The system keeps up by running longer and harder, which is often invisible until a compressor fails on a hot week in July.
Decent maintenance in a warehouse is not copy-paste from an office. Coil cleaning frequency has to match the dust profile of the operation, sometimes doubling during peak season. Filters in ventilation units should be specced for the real particulate load. I often replace G4 panels with a staged approach, moving to a pre-filter plus a higher grade final. It adds a small pressure drop, which you can absorb by adjusting fan speeds, and the energy trade-off is better than running coils dirty. Keep records of delta-P across filters and coils. TM44 inspectors love to see trend lines, and so do I, because they flag when cleaning actually saves money instead of just meeting a calendar rule.
One other recurring note: refrigerant charge. Slow leaks are easy to miss when the system appears to “work.” Inspectors will flag evidence of ice buildup or low superheat. A simple regime of leak checks and weighed-in charge logs prevents chronic underperformance and, more importantly, keeps you on the right side of F-gas obligations.
Zoning that never matched the workflow
Warehouses evolve constantly. A returns area takes over part of bulk storage. A kitting line moves closer to dispatch. HVAC zones seldom keep up. TM44 reports often point to oversized systems trying to maintain a temperature in a space that is now half its original size, or to a single thermostat commanding multiple rooms with different gains and occupancy.
Re-zoning sounds expensive, but it does not always require new plant. Ductwork can be rebalanced. VAV boxes can be added where access allows. In split-system land, you may consolidate two underutilized indoor units and decommission the rest. The trick is to align zones with thermal behavior rather than with purely architectural boundaries. Group together zones with similar solar exposure and occupancy, and avoid tying open warehouse space to small enclosed offices. The investment returns faster where shift patterns vary, because a zoned system makes setbacks meaningful. Inspectors will recommend that kind of rationalization when they see persistent comfort complaints in one corner and wasted cooling in another.
Heat rejection in the wrong microclimate
Roof condensers on large flat roofs face brutal conditions: reflected solar gain, stagnant air, and sometimes heat recirculation when units cluster. Ground-level condensers near loading docks fight hot exhaust from idling lorries. TM44 write-ups frequently mention high condensing temperatures and short cycling under peak loads. You can throw capacity at the problem, but the better solution usually involves airflow.
Spacing and elevation matter. Lifting condensers slightly above the roof plane helps reduce recirculation. Avoid back-to-back arrays with less than the manufacturer’s clearance. Where the layout is tight, baffles can redirect discharge air. I have also seen success with light-colored roof coatings around condenser banks to cut local heat island effects by a few degrees Celsius, small on paper but enough to drop condensing pressure during heatwaves. If the site allows, shifting some condensers to the shaded north elevation can add resilience. None of this requires new plant, just deliberate attention to the microclimate you create around the kit you already own.
Overventilation that throws money out of the door
Warehouse operators often equate ventilation with freshness and safety, so they run fans at full tilt all day. TM44 inspections commonly find ventilation rates far above code minima, especially in spaces without significant contaminants. This is compounded by habitually open dock doors. The net effect is a river of conditioned air leaving the building while the AHU keeps trying to hold a setpoint that never stabilizes.
Right-sizing ventilation starts with demand. For low-risk areas, CO2 sensors can trim fresh air while keeping indoor air quality well within limits. In process areas where contaminants are present, local extraction may carry the burden better than whole-space dilution. For doors, air curtains can help, but only when sized, positioned, and maintained properly, and when staff do not prop them into bypass. An alternative that works in cross-docks is to treat the dock zone as a buffer with relaxed setpoints and to condition only deeper interior zones. Clear signage and training help the operational team understand why doors slightly ajar cost far more than they seem. I often share a week of energy data with supervisors after adjustments. Seeing a 10 to 20 percent cut in fan energy, plus steadier space temperatures, tends to build buy-in.
Part-load inefficiency in legacy equipment
Many warehouses run legacy DX systems sized for peak summer days that occur maybe 20 to 40 hours a year. The rest of the time, those systems cycle around low loads. Without inverter drives or staged compressors, they struggle to operate efficiently. TM44 reports regularly recommend variable speed retrofits or staged capacity.
Here is the nuance. A full kit replacement promises big savings, but the economics hinge on runtime. If your cooling hours sit below 1,000 per year, a well-aimed retrofit might outperform a wholesale change-out in pure payback terms. Adding EC fans to AHUs, fitting VSDs on supply and extract, and upgrading controls often captures 60 to 80 percent of the saving for a fraction of the cost. When the system is at end of life anyway, the case for new high-SEER equipment tightens, especially if refrigerant phase-down factors push prices up on older gases. Inspectors will not tell you to spend money for its own sake, but they will point to the parts that burn kWh at part load.
Poor airflow around racking and mezzanines
Racking creates obstacles that designers cannot always predict. A neat CFD model from the design stage rarely matches the reality of a narrow aisle that now stores wrapped textiles or a bay that holds battery-powered equipment generating heat. TM44 inspections highlight hot and cold spots because uneven temperatures drive short cycling and complaint-driven setpoint drops.
You do not always need more capacity to fix this. Re-aim diffusers, add adjustable nozzles for throw, and remove accidental blockages such as temporary signage mounted over grilles. Destratification fans positioned between rack tops and the soffit can even out vertical temperature gradients. Pay attention to safety and clearance, especially around sprinklers. I have walked sites where simply rotating two supply terminals reduced a four-degree aisle-to-aisle temperature swing. Logging temperature across typical pick paths exposes the true problem areas. Solving for uniformity often allows you to raise cooling setpoints slightly without affecting comfort, which saves energy both directly and in reduced cycling.
Documentation gaps that stall progress
TM44 requires evidence: asset lists, maintenance history, control narratives. Warehouses, particularly those that have grown in phases, often lack a single source of truth. The inspector notes “unknown make/model,” “no record of commissioning,” or “setpoints undocumented.” These are not tick-box complaints. Without a map of the system, you cannot execute even modest improvements with confidence.
One of the easiest wins is to create a live, lightweight asset register. QR-tag each indoor and outdoor unit, linking to photos, model numbers, filter sizes, and last service dates. Store control schedules in the same folder. Keep a one-page system diagram for each zone showing sensor locations, airflow direction, and damper positions. I prefer a format simple enough for a shift manager to understand, because that is who will spot when reality diverges from the drawing. The next TM44 visit becomes faster and more useful, and in the meantime your team will waste less time just figuring out what they own.
The energy mix and the heating question
Even when TM44 focuses on cooling and ventilation, heating lurks in the background. Gas-fired radiant tubes or unit heaters often run while cooling protects equipment or a small number of workers in a hot corner. Inspectors highlight simultaneous heating and cooling as a clear inefficiency. The right answer varies by warehouse type. In a high-bay ambient facility, radiant heat is usually the most efficient way to make people comfortable in winter, because it warms people and surfaces without trying to heat all the air. Pairing radiant heat with local cooling for equipment is acceptable, but you must physically separate the zones enough so that the cooling does not counteract the radiant effect.
Where electric pricing structures and carbon policy steer you toward electrification, consider heat pumps that serve offices and enclosed production rooms, while keeping radiant for open bays. Hybrid approaches can be the sweet spot for the next five to ten years. Inspectors will not prescribe your energy pathway, but they will call out poor pairings and encourage better zoning.
Seasonal setpoint drift and the human factor
I have almost never seen a warehouse that did not suffer from setpoint sprawl over time. A heatwave leads to a temporary drop in setpoints. Winter overtime pushes schedules later. Someone installs a portable unit for a bottleneck process and forgets it after the season. By the time the next TM44 arrives, every system is running harder than the design intended.
This is a management problem as much as a technical one. Establish a rhythm for seasonal review. Every April and October, run through setpoints, schedules, and sensor calibrations. Ask supervisors to flag hotspot changes and temporary processes. Make it easy for them by giving a simple form or short walkabout. Then lock your default bands and require a note for any changes. I am not a fan of rigid controls that remove local authority, because warehouses need flexibility, but a light layer of governance keeps energy use from ballooning in quiet increments.
What good looks like after a TM44
The best post-inspection outcomes share a few traits. The team chooses the right scale for action. They grab low-hanging controls changes quickly, because those start saving money within days. They plan medium-cost fixes like sensor moves, minor ductwork adjustments, and fan upgrades during scheduled downtime. They use data to make hard choices on replacement or retrofit. And they keep the inspector’s report visible, treating it as a punch list that ties directly to monthly energy spend and comfort outcomes.
When I review progress with a warehouse six months after an inspection, I look for a handful of changes: cleaner coils and filters on a realistic schedule, tighter and documented setpoints, fewer overlapping zones, adjusted ventilation rates matched to occupancy, and a slightly flatter temperature profile across key aisles. If we see 10 to 25 percent reduction in HVAC electricity use alongside fewer comfort complaints, the plan worked.
Practical fixes ranked by effort and impact
Choosing where to start can feel overwhelming. Below is a compact prioritization that aligns with typical TM44 findings and the realities of a working warehouse. Keep it as a guide, not a rulebook.
- Very low effort, high return: widen deadbands by 1 to 2°C, correct obvious schedule errors, disable simultaneous heating and cooling where possible, relocate blocked sensors or clear obstructions from return grilles. Low to moderate effort: clean condenser and evaporator coils, upgrade to better-suited filters with monitored pressure drop, add or reposition destratification fans, tweak diffuser throws to match racking. Moderate investment: add VSDs to AHU fans, fit EC plug fans in place of belt drives at next service, re-zone small office and welfare areas, implement CO2-based ventilation control in low-risk areas. Targeted capital: replace worst-performing legacy splits with inverter units, reorganize condenser layout to avoid recirculation, add air curtains or create a buffer dock zone with relaxed setpoints. Strategic upgrades: when end of life approaches, shift to high-SEER equipment or heat pumps for enclosed spaces, retain or improve radiant heating for large open bays, and integrate simple BMS functions for alarms and schedules.
Common pitfalls when acting on TM44 advice
It is easy to overcorrect. Cutting ventilation too aggressively can spike CO2 and hurt alertness in pick areas. Overusing air curtains without maintaining them leads to noise and drafts that staff quickly bypass. Installing more sensors without a plan to use the data adds complexity without clarity. And the classic misstep: replacing equipment before fixing controls, which leaves savings on the table.
Run small pilots. Try revised setpoints in one aisle bank for two weeks and log feedback. Commission two TM44 air curtains properly and measure door-zone temperatures before rolling out ten. A measured approach keeps morale and performance intact while you bank savings.
Real numbers from the field
A 30,000 square meter ambient warehouse in the Midlands cut HVAC electricity by roughly 18 percent over three months by taking four steps: widened office deadbands from 21 to 24°C cooling and 20 to 18°C heating, reduced nighttime ventilation to 20 percent with CO2 override, cleaned and straightened condenser fins on 14 rooftop units, and moved three return sensors from ceiling height to the occupied zone. No new equipment. The TM44 that preceded these changes had highlighted short cycling and sensor placement as key inefficiencies.
Another site, a 12,000 square meter e‑commerce facility with mezzanine pick levels, struggled with 5 to 6°C gradients between floor and mezzanine. Adding destratification fans and retuning diffuser throws flattened the gradient to 2 to 3°C. That allowed a 1°C increase in cooling setpoint without complaints, producing an estimated 6 to 8 percent energy saving during summer weeks. Maintenance workload stayed about the same, offset by fewer reactive callouts.
Getting ready for your next TM44
Treat the inspection as free consulting tied to statutory compliance. Ahead of the visit, make sure your asset list is current, filters and coils are in good shape, and setpoints reflect the season. Walk the building and note any obvious conflicts such as doors without effective air separation or zones where heating and cooling overlap. Highlight any recent operational changes so the inspector can consider them in context. The more you share, the more useful the findings will be.
If you take only one principle from this article, let it be this: align your HVAC with the warehouse you actually run, not the one on the drawings. TM44 is a tool to expose misalignments and point toward practical, staged improvements. Fix the controls, place the sensors where people are, keep the air paths clean and intentional, and match ventilation to need, not habit. Do that, and your next report will read like a progress note rather than a to-do list.