Warehouses rarely TM44 enjoy the thermal forgiveness of office buildings. High ceilings, large doors, racking that disrupts airflow, mixed-use areas like packing stations and cold corridors, and a rotating cast of forklifts and people all conspire to make temperature control both expensive and difficult. Add the legal requirement for periodic air conditioning inspections under TM44, and the stakes rise. Done well, a TM44 inspection is more than a tick-box exercise. It can sharpen your plant strategy, reduce energy spend, and head off failures long before they cause downtime. Done poorly, it drains time and yields generic advice that never leaves the PDF.
This guide lays out how to approach TM44 in a warehouse environment with practical depth. It blends the compliance backbone of the scheme with the realities of running large, variable spaces, and it explains how to get genuine value from the process.
What TM44 actually requires
TM44 refers to the guidance associated with Energy Performance of Buildings Regulations inspections for air conditioning systems. In the UK, if your building has air conditioning systems with a combined rated output of 12 kW or more, you must have a TM44 inspection at least every five years by an accredited assessor. The rule applies per site, not per unit, and it captures both comfort cooling and packaged units attached to process areas when they serve occupied spaces.
The inspection is documentary and visual. Assessors review system design, maintenance records, control strategies, refrigerant management, and energy performance. They do not dismantle plant, but they may sample coils, filters, and accessible ducts. The deliverable is a report with recommendations ranked by impact and feasibility. While the recommendations are not legally binding, non-compliance with the inspection itself can lead to enforcement action and fines from local authorities. More quietly, missing inspections invites insurance questions after an incident, particularly where refrigerant leakage or poor maintenance is involved.
Two points often misunderstood: first, TM44 is technology-agnostic. It applies to split systems, VRF/VRV, rooftop packaged units, and even chillers serving air handling units if they provide comfort cooling to occupied zones. Second, the 12 kW threshold is the sum of systems under common control within a building. Five 3.5 kW splits supplying a mezzanine picking area almost certainly trigger the requirement.
Why warehouses have a different TM44 risk profile
TM44 was written to be building-type neutral, but warehouses test its boundaries. The risk profile differs for three reasons.
The operating envelope is wider. Many warehouses allow temperature swings that would be unacceptable in offices, especially in racked storage. That tolerance often hides failing systems until peak summer or a heatwave exposes them. By then, replacement lead times, access equipment, and night work premiums magnify costs.
The geometry is unforgiving. High bays and local heat sources demand careful airflow design. Lightweight splits pushing cold air from 7 meters up will fight stratification and lose. That mismatch shows up in TM44 findings as poor control, simultaneous heating and cooling, and short cycling, all of which drive energy waste.
The plant mix is patchy. It is common to inherit a patchwork of units: a dozen wall-mounted splits in picking, a bank of cassettes over pack benches, a couple of rooftop units for offices, and an unloved pair of ducted units serving the returns area. Spares, filters, and controls vary across manufacturers and vintages. Documentation is thin. A good TM44 inspection will highlight this fragmentation, because it often causes poor maintenance, uneven setpoints, and duplicated controls.
Documentation that makes or breaks the inspection
Most of the value in TM44 arrives through evidence, not guesswork. You can transform the quality of recommendations by preparing a tight pack of documents and data. For a typical 10,000 to 30,000 square meter warehouse, the following items allow an assessor to be precise rather than generic:
- An up-to-date asset register with make, model, serial number, REFCOM leak check class, and rated capacity for each unit, tied to a simple line-drawn plan with unit tags. The past 12 to 24 months of maintenance records, including F-gas checks, leak repairs, and pressure test results, plus any coil cleans and filter replacements with dates. Control strategy notes: setpoints, schedules, occupancy assumptions, deadbands, and any lockouts preventing heating and cooling from running together. Energy data, at least monthly, for sub-meters feeding HVAC if available, or otherwise the whole-site profile with notes on seasonal drivers and operational changes. As-installed drawings or a redline sketch for air handlers, duct routes, and major plant, especially where rooftop units serve multiple zones.
Every missing item pushes the assessor toward conservative estimates and generic advice. Warehouse operators regularly uncover hidden savings simply by consolidating this information across sites. One operator in the Midlands found three model variants of the same cassette unit, each with a different filter size and replacement interval. Standardizing filters cut service visits by ten percent in the first year.
The walk-through: what good looks like
A competent assessor blends compliance checks with performance instincts. In a warehouse, the site walk is where most of that comes together. Expect them to seek evidence of three things: airflow quality, control discipline, and refrigerant integrity.
Airflow quality is visible in the dirt pattern. Dark crescents on ceiling tiles around cassettes often mean the units are entraining dusty air because filters are clogged or the fan is set too high. Coils that look clean under a torch can still be matted on the condenser side outdoors. In high-bay areas, look for temperature stratification markers such as frost damage on top tiers in winter or sweaty shrink wrap at shoulder height in summer. A simple handheld temperature probe placed at floor level and seven meters up tells you more than most BMS screens. If your aisles run long and straight, air throws should be checked at full fan speed against the aisle length. Many cassette configurations dump air half across the aisle, which recirculates heat and defeats the cooling pattern.
Control discipline means setpoints that make sense by zone and time. Mixed-use warehouses often leave pack bench areas at 19 degrees all year because staff complain about heat. That creates a persistent cold sink that drags on neighboring zones, so nearby units run harder. A mature control strategy establishes a temperature corridor per zone, a deadband of at least 2 degrees, weekday and weekend schedules, and a rule that heating and cooling cannot be active together without a verified load case. If you have a BMS or even smart controllers from different manufacturers, the assessor should test a schedule change at one representative unit and verify it executes. Silent setpoints that never reach the controller are a common cause of phantom loads.
Refrigerant integrity is partly paperwork and partly physical. F-gas records overdue by months, no leak test stickers, and unclear refrigerant types create compliance risk. Systems on R22 should no longer be in service; legacy R410A and R407C units still dominate, though many operators have started moving toward lower GWP blends. The assessor may recommend replacing linesets with contaminated oil residues where retrofit to lower GWP refrigerants is planned. Outside, oil staining at service valves, missing caps, and corroded flare joints deserve immediate attention. Inside, a unit that needs top ups year after year is a leak until proven otherwise. Expect the assessor to call that out.
Using TM44 to constrain energy spend
Energy is the line item you can influence most through TM44 recommendations. Warehouses sometimes assume the fabrication of the building dictates energy performance and that air conditioning is a small, unchangeable slice. That’s true for unconditioned racked areas, but not for packing halls, mezzanines, or offices within the box. Through TM44, you can usually find savings between 5 and 20 percent of HVAC electricity without capital-intensive changes.
Start with scheduling. Many warehouses run cooling an hour before shift and an hour after, regardless of ambient conditions. If you record the indoor temperature profile for a week using inexpensive loggers, you often discover that pre-start cooling beyond 20 to 30 minutes yields no comfort gain. A documented change like this is exactly the sort of recommendation an assessor can formalize in the report, giving operational cover to enforce it.
Setpoint discipline pays back. If your pack area is at 20 degrees because of heat stress concerns, gather data on task metabolic rates and consider 23 to 24 degrees in summer with high air movement. Fans make people feel cooler because of evaporation, and moving from 20 to 23 degrees can trim compressor run time significantly. Provide the assessor with data from the hottest week of last summer and your staffing profile; they can then frame a recommendation backed by comfort standards and practical limits.
The next lever is demand control. Occupancy sensors for warehouse zones can be clumsy, but door switches at high-traffic goods-in areas or interlocks with dock levellers make a measurable difference. A unit blasting cold air into a zone with roller shutters up is wasting money. Interlocks that relax setpoints or switch to fan-only while doors are open add resilience. Assessors like to recommend these because they reduce simultaneous heat gains and compressor load without changing worker experience.
Finally, right-size your filtration schedule. Dirty coils drive head pressure up. But overservicing also costs. Move to differential pressure or visual criteria rather than calendar intervals when possible. Where that is not feasible, segment filter intervals by dust risk. A returns area with constant cardboard dust needs shorter cycles than clean admin offices. TM44 reports rarely dive deep into filter logistics, yet more than once we have seen a ten to fifteen percent improvement in system efficiency after a coil deep clean and a revised filter program.
When replacement beats repair
A TM44 assessment should flag units that are past their economic life or out of step with refrigerant policy. In warehouses, lifecycle decisions often revolve around access, downtime, and control integration, not just energy. The trigger points are clearer if you look through four lenses: age and refrigerant, maintenance cost trend, control compatibility, and access risk.
Age and refrigerant go together. If a unit is over 12 to 15 years old and runs R410A, you are facing a medium-term path toward lower GWP options. Retrofits may be possible but can be false economy if coils and linesets are tired. A planned program that swaps entire clusters of units zone by zone reduces parts variability and simplifies control. The TM44 report can formalize a roadmap with prioritization based on leak history and criticality.
Maintenance cost trend matters more than one-off repairs. A unit that needed a fan motor last year and a coil clean this year is not automatically a replacement candidate. What tips the balance is repeated refrigerant losses, seasonal trips, or control boards that fail and are no longer available. Ask your assessor to review two to three years of repair invoices if you have them. Many reports stop at snapshots, but trends tell the real story.
Control compatibility is often overlooked. If you are standardizing on a particular BMS or a cloud gateway, a mismatched island of legacy splits increases the chance of simultaneous heating and cooling as zones fight. Replacing those units to integrate with your chosen controls can yield outsized savings relative to the capital outlay.
Access risk is specific to warehouses with high bays or mezzanines. If a unit requires a 20-meter cherry picker and a night shift every time a board fails, your total cost of ownership rises fast. A TM44 recommendation that relocates plant, switches to rooftop packages with safer access, or consolidates units into a serviceable cluster can pay back through maintenance safety alone.
Controls: the quiet multiplier
Controls are where most TM44 recommendations either fail or flourish. Warehouses often run units with local IR remotes because the install was fast and cheap. The result is a patchwork of setpoints, modes, and timers that drift as people override them. Even a light-touch central control layer improves stability.
There are three workable approaches for most warehouses. One is manufacturer-specific central controllers that bring groups of splits into a unified schedule and setpoint policy. The second is multi-brand gateways that pull key parameters into a dashboard, useful for estates with mixed kit. The third is a simple rules engine using smart thermostats and lockable cases in critical zones. None of these need be expensive or complicated to get 80 percent of the benefit.
During TM44, push the assessor to test control enforcement. Ask them to verify that heat-cool lockouts work, deadbands are at least 2 degrees, and fan speeds auto-adjust before the setpoint kicks compressors into high demand. Also, get a recommendation about naming conventions and zone maps. “Pack Bench North - Cassette A1” beats “Unit 3” in every way when something goes wrong at 4 pm on a Friday.
Special warehouse challenges the report should address
Not all warehouses are the same. A few patterns recur often enough to deserve explicit treatment in the TM44 report.
Mezzanines over heat sources drive local hotspots in summer and cold toes in winter. If you position cassettes at mezz level without underfloor mixing, stratification wins. The remedy includes destratification fans, carefully aimed supply air, and acceptable setpoint compromises. Ask for a recommendation that quantifies fan run time and expected temperature equalization so facilities can defend the change.
High infiltration near loading docks undermines cooling. Weather curtains, fast-action doors, and air curtains help, but only if controls recognize door states. Many air curtains run constantly, wasting energy. A better approach ties them to door triggers with timed extensions and ensures nearby cooling backs off during door-open periods.
Process zones that generate heat, from battery charging to shrink tunnels, should be separated thermally if possible. Where they cannot be separated, prioritize local extraction or displacement ventilation to move heat at source. A TM44 inspector should call out simultaneous heat generation and cooling as a red flag and suggest low-cost segregation steps.
Cold storage adjacency is an edge case. Cold rooms leak chill into surrounding areas and may cause condensation on ductwork or unit casings. Insulate and vapor-seal any exposed pipes near chilled spaces. Ask the assessor to review dew point risk at interface zones and call for anti-sweat controls if needed.
Health, safety, and legality that hide behind the energy story
TM44 is a compliance framework tied to energy performance, but health and safety runs through the details. In warehouses, where access to plant often involves working at height, lockable isolation, safe roof access, and proper fall protection are not optional. A strong report will flag unsafe access routes, missing guards around rooftop condensers, and the lack of safe work platforms.
F-gas compliance deserves special attention. Ensure your contractor is REFCOM or equivalent accredited, keep leak check intervals aligned with refrigerant charge thresholds, and tag units after tests. If your estate crosses jurisdictions or you operate leased sites with shared services, clarify who owns the F-gas duty. TM44 won’t resolve legal ambiguity, but it can document it and push landlords or tenants to assign responsibilities.
Legionella is usually a water-side issue, yet evaporative condensers and adiabatic systems occasionally appear around warehouses. If you have any evaporative equipment tied to cooling, the assessor should reference water hygiene controls and risk assessments. That note can save you from a regulatory blind spot.
Extract value from the recommendations
A thick report helps nobody unless it translates to action. Treat the TM44 output as a mini program, not a document to be filed. The simplest way to move is to assign owners, dates, and budgets to a short set of measures that hit three buckets: zero-cost control changes, low-cost maintenance upgrades, and targeted capital.
Zero-cost changes typically include schedule tweaks, setpoint corridors by zone, and lockout enforcement. These can start within a week. Low-cost maintenance upgrades include coil deep cleans on underperforming units, filter cadence changes, and sealing obvious duct leaks. Capital items might be a handful of destratification fans, a central controller for splits, or sensor kits for dock doors.
Track results even if roughly. A monthly HVAC kWh versus degree days tone-of-the-graph can show whether the measures landed. Many operators rely solely on bills and anecdotes, which dulls the case for the next site. When senior leadership sees a 12 percent reduction in HVAC consumption through the same three measures at three different warehouses, they fund the program.
Practical examples from the floor
At a 15,000 square meter e-commerce warehouse with 24 packing benches, the TM44 inspection highlighted 18 cassettes fighting each other. Half were in cooling at 20 degrees, half in auto at 22 degrees, and all fans were set to high manually. After a one-day controls tidy-up, a 2-degree deadband, and a rule to keep fans on auto, compressor run hours dropped by roughly 17 percent in the next billing cycle even though outside temperatures were similar. The report’s value was not the idea itself, but the documentation that let operations hold the line.
Another site in a coastal region had persistent refrigerant losses from rooftop units, blamed on sea air. The assessor traced the issue to missing service caps and poorly supported linesets that vibrated against parapets. A modest project added proper supports, replaced flare joints with brazed connections, and put locking caps on all ports. Leak rates fell to near zero for the following year. Energy use also dipped because the systems were no longer running with low charge.
A third warehouse with a high-bay mezzanine had workers complaining of heat stress during a warm spell. Infrared scans taken during the TM44 walk showed a 6-degree difference between floor and mezzanine level in the same aisle. Installing five destratification fans and moving setpoints up by 1 degree, combined with a change in shift break timing to avoid the 3 pm solar peak in the packing area, stabilized temperatures within 2 degrees vertically. The TM44 report provided the rationale and recommended fan spec, which sped procurement.
Cost, downtime, and the rhythm of the year
The best time for TM44 in a warehouse is shoulder season, typically spring or early autumn. Units can be run under mild load, access equipment is easier to schedule, and recommendations can be implemented before the next thermal peak. Inspections on a medium site may cost from a few hundred to a couple of thousand pounds depending on system count and complexity. Downtime for individual units during the inspection is minimal, but any follow-on coil cleaning or control work should be slotted into low-volume periods. Night work is expensive. The report can help justify daytime windows if it demonstrates that only a subset of units need intervention at a time.
Tie TM44 into your broader asset plan. If you audit lighting, racking changes, or mezzanine upgrades, align those timelines. Moving a cassette after new racking is painful. Rebalancing airflow once the floor plan shifts is cheaper than fighting hot spots forever. A good assessor will ask about upcoming changes and shape recommendations so you can sequence decisions.
What to ask your assessor before you hire them
The difference between a boilerplate report and a useful one is the assessor’s grounding in warehouse operations. Before commissioning, ask three questions: Have they completed TM44 inspections for large logistics or industrial spaces, not just offices? Do they incorporate spot measurements of temperature stratification and airflow, not just visual checks? Will they review your control strategies in enough detail to recommend concrete setpoints, deadbands, and lockouts for each zone?
Also, clarify deliverables. You want a prioritized action list with estimated savings ranges, ballpark costs, and dependencies, not just “consider improving controls.” Agree on the format of asset registers and the mapping convention so you can reuse the data across sites. Small details like consistent unit tags become invaluable when you scale.
Compliance as a catalyst
TM44 is a compliance duty, but in warehouses it is also a lever. The environment is chaotic by nature. Pallets move, doors open, seasons swing, and staff comfort matters. By treating the inspection as a structured chance to reset controls, clean up documentation, and plan replacements, you convert a regulatory tick into operational performance.
Two or three cycles into a well-run TM44 program, patterns emerge. Units that always drift out of spec stand out. The same handful of recommendations carry over from site to site, so you build standard playbooks. Energy shrinks as a percentage of operating cost, and reactive maintenance gives way to planned interventions that fit your shift rhythm. Most important, you stop arguing about temperatures with anecdotes and start making changes with data.
For warehouses, that is mastery: not perfection, but control. TM44 gives you the scaffolding. The craft lies in the details you feed it and the discipline with which you act on what it reveals.