If your building’s air conditioning systems have a combined effective rated output above 12 kW, you need a TM44 inspection carried out by an accredited assessor, and you need one at least every five years. “Combined capacity” means the total output of every comfort cooling system in the building added together, not just the biggest unit in the plant room. Two 8 kW split systems serving different floors still push you over the threshold.

Your next move is straightforward:

Check the nameplate or O&M manual data on each cooling unit for its rated output
Add up every comfort cooling system across the building, not just the largest single unit
If you’re unsure whether the total clears 12 kW, ask an accredited assessor to verify before assuming you’re exempt

Pro Tip: Don’t rely on memory or old paperwork for capacity figures. Manufacturers’ data plates and O&M manuals hold the definitive numbers, and mismatched records are one of the most common reasons a compliance check drags on longer than it should.

Key Takeaways

TM44 inspections are legally required every five years for any commercial building with combined cooling capacity above 12 kW, and treating the report as a live maintenance input rather than a filed certificate is what actually protects both compliance and energy budgets.

Point	Details
Check the 12 kW threshold	Add up every comfort cooling system’s rated output; multiple small units often push buildings over the line.
Confirm who’s responsible	Whoever controls the system, not always the owner, must arrange and hold the report.
Verify assessor accreditation	Ask to see scheme ID and registration level before booking, and confirm they will lodge the report.
Budget realistically	Costs typically range from £400 for small sites to over £1,200 for larger, multi-system properties.
Act on findings promptly	Fold recommendations into planned maintenance; Delta First combines TM44 inspections with PPM scheduling across its serviced regions.

Which buildings and systems fall under TM44 inspection requirements?
Who is legally responsible for arranging a TM44 inspection?
What happens during an inspection and what should the report include?
How do you choose and appoint an accredited TM44 assessor?
What does a TM44 inspection cost and how long does it take?
How should you act on TM44 recommendations after the inspection?
How Delta First delivers a compliant TM44 inspection
Why treat TM44 as a maintenance tool, not a compliance chore
Book a TM44 inspection with Delta First
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Which buildings and systems fall under TM44 inspection requirements?

TM44 catches far more buildings than most facilities managers expect. Offices with central chiller plant are the obvious case, but hotels, retail units, warehouses with climate-controlled storage, schools, and hospitals all commonly exceed the 12 kW threshold once every comfort cooling system on site is totted up.

The system type matters less than the combined output. VRF and VRV systems, packaged chillers, rooftop units, and multiple wall-mounted split units all count towards the same total if they’re providing comfort cooling. A building with six 3 kW split units scattered across offices has 18 kW of combined capacity, comfortably over the line, even though no single unit looks significant on its own.

There’s a distinction worth understanding here: TM44 applies to comfort cooling, meaning systems that condition space for people. Process cooling, such as equipment purpose-built to keep manufacturing machinery or specialist refrigeration running, generally sits outside scope, though the boundary isn’t always obvious. Server rooms are a genuine grey area, since some server cooling counts as comfort conditioning for the space and some doesn’t, depending on how the system is configured and what else it serves.

To confirm your position, follow this sequence:

Pull the nameplate data or manufacturer specification sheet for every cooling unit in the building
Cross-reference against O&M manuals, which usually list rated output more precisely than a nameplate alone
Sum every comfort cooling system’s output, ignoring units dedicated solely to process cooling
Where the total sits close to 12 kW, or where server rooms, shared multi-tenant plant, or mixed-use buildings complicate the picture, get an accredited assessor to verify capacity before you assume either way

Pro Tip: Shared buildings with multiple tenants are a frequent blind spot. If your organisation only manages part of a building, the combined capacity calculation still applies to the whole structure, so speak to the landlord or managing agent about who else’s plant needs counting.

Who is legally responsible for arranging a TM44 inspection?

The statutory basis for TM44 sits in the Energy Performance of Buildings (Certificates and Inspections) (England and Wales) Regulations 2007, which requires inspections of air conditioning systems above the capacity threshold. GOV.UK’s own guidance sets the practical detail: any building in England and Wales with combined cooling output over 12 kW must be inspected at least every five years.

Responsibility falls on whoever controls the system, which is not automatically the building owner. In a leased office, that might be the tenant’s facilities team if the lease gives them operational control of the plant. In a multi-let building, it’s often the landlord or managing agent, since they typically control shared HVAC infrastructure. Where a dispute arises over who holds responsibility, the safest approach is to check the lease terms for maintenance and plant control clauses, and where ambiguity remains, both parties should agree responsibility in writing rather than assume the other is handling it.

Enforcement works through local trading standards or building control officers, who have the power to request a valid TM44 report at any point. If you can’t produce one, or the one you hold has expired, you’re exposed to fixed penalty notices. Government implementation reporting on the regulations makes clear the intent behind enforcement is not purely punitive; it’s designed to push building operators towards identifying inefficiencies and cutting energy use. That said, compliance guides published through 2024 and 2025 point to strengthened enforcement and improved central registers, meaning the days of a quiet word and a grace period are numbered.

Recordkeeping matters more than most facilities teams treat it:

Keep a copy of every TM44 report accessible on-site or in your compliance file, not just with your managing agent
Retain proof of statutory lodgement, since a report your assessor never lodged doesn’t count as compliant
Log the renewal date somewhere your PPM or compliance calendar will actually flag it, five years pass faster than most people expect

What happens during an inspection and what should the report include?

An assessor doesn’t simply glance at your plant room and sign a form; instead, they thoroughly review Siemens thermostats and controls as part of the detailed inspection process. A proper inspection under CIBSE’s TM44 guidance, the technical standard underpinning UK compliance, involves identifying every piece of cooling plant, checking rated capacities against nameplate and O&M data, and reviewing how controls and zoning are actually configured against how the building is used.

On-site, expect the assessor to:

Identify and log every cooling system, cross-checking capacity against documentation
Review controls and zoning to see whether the system matches current occupancy patterns
Examine maintenance records and operating history for signs of inefficiency or neglect
Sample performance where practical, comparing actual running behaviour against design intent

This isn’t a cosmetic check. TM44 assessment explicitly requires review of controls, zoning, and maintenance records alongside energy-saving recommendations, not just a walk-round with a clipboard. A chiller running at full output for a floor that’s been empty for two years, for example, is exactly the kind of mismatch a competent assessor should flag, and exactly the kind of finding that saves real money once actioned.

A compliant TM44 report needs to show:

A clear system description covering every cooling unit inspected and its rated capacity
Findings from the on-site assessment, including any deficiencies in controls, zoning, or maintenance
Specific improvement recommendations, not vague statements about “efficiency opportunities”
A statement confirming the assessor’s accreditation and scheme membership
Evidence of statutory lodgement, ideally a reference number you can quote if challenged

Enforcement officers use this report as their primary evidence when they request proof of compliance, and building owners use it as the baseline for planning remedial works. A report missing any of these elements isn’t just weak, it may not stand up if a local authority asks to see it. If you’re a facilities manager overseeing several sites, it’s worth treating the report format itself as a quality check on the assessor, since a rushed or generic document is often a sign the inspection itself was rushed too.

How do you choose and appoint an accredited TM44 assessor?

Not every HVAC contractor can legally issue a TM44 report. You need someone holding current membership of an approved accreditation scheme, typically at Level 3 or Level 4 assessor status depending on system complexity, and you should ask to see their scheme ID and registration number before instructing them, not after.

Follow this appointment sequence:

Request evidence of accreditation scheme membership and current assessor level, matched to your system’s complexity
Confirm they can lodge the finished report on the statutory register and will provide proof of lodgement, not just a PDF emailed to you
Ask about turnaround time from site visit to lodged report, and what access to plant rooms and roof units they’ll need arranged in advance
Clarify what’s included in the quoted cost, travel, report lodgement fees, and any follow-up consultation on recommendations
Establish exactly what evidence you’ll receive: the report itself, the lodgement reference, and ideally a plain-English summary for non-technical stakeholders

Pro Tip: If you manage several sites, ask whether the assessor can schedule multiple properties in a single visit window. Grouping inspections across a portfolio often reduces per-site cost and means every report lands with a similar renewal date, which makes future scheduling far simpler.

There’s a real procurement advantage in combining TM44 with an existing planned maintenance relationship rather than treating it as a one-off purchase from a separate specialist. Facilities teams that fold TM44 recommendations into their PPM contracts tend to see lower unit costs and faster remedial turnaround, since the contractor already has site access, plant history, and a working relationship in place rather than starting cold. Delta First’s approach to air conditioning consulting reflects exactly this logic: assessment and maintenance sit under one accountable partner rather than two disconnected suppliers.

What does a TM44 inspection cost and how long does it take?

Costs vary by site size and complexity, and the ranges published across the industry reflect that spread clearly. Small single-system sites tend to sit around £400 to £600, medium commercial properties with several systems typically run £700 to £1,200, and larger or multi-plant sites climb higher depending on the number of separate systems and how accessible they are.

Access is the variable that catches people out. A rooftop chiller behind a locked hatch with no permanent ladder access adds time to the visit and, often, cost to the quote. So does a building where maintenance records are scattered across three different contractors rather than held centrally.

Typical on-site inspection time runs from a couple of hours for a straightforward single-system office to a full day or more for a large site with multiple plant rooms. Report delivery usually follows within one to two weeks of the site visit, assuming documentation was available on the day.

The costs that catch facilities teams unprepared are rarely the headline fee. Watch for:

Incomplete or missing O&M documentation, forcing the assessor to spend extra time verifying capacity manually
Inaccessible plant that requires a second visit once proper access has been arranged
Remedial work identified during inspection that wasn’t budgeted for separately

The most reliable way to control cost is to have your capacity documentation ready before the assessor arrives, and to schedule the visit alongside other compliance or maintenance work already planned for the site. Bundling a TM44 visit with a routine HVAC service call, for instance, often means the assessor and engineer share access arrangements, cutting disruption and sometimes cost.

How should you act on TM44 recommendations after the inspection?

A TM44 report that sits in a drawer achieves nothing beyond satisfying an enforcement officer’s paperwork request. Its real value comes from what you do with the recommendations.

Sort recommendations into three tiers: legal or safety risk first, high payback with low disruption second, and everything else third
Fold the priority items straight into your existing PPM schedule rather than treating them as a separate project, since your maintenance contractor already has the site knowledge to act quickly
Document every repair and improvement as it’s completed, including dates, invoices, and before-and-after evidence where relevant
Where remedial works can’t happen immediately, note a realistic rebooking date and keep evidence of that plan, since enforcement officers respond far better to a documented programme than a report with no follow-up

Capital-heavy recommendations, replacing an ageing chiller, for example, belong in your longer-term capital planning rather than an emergency budget line. Smaller items, like recalibrating zone controls or adjusting operating schedules to match actual occupancy, often cost little and can be actioned within weeks. Treating TM44 as an input to ongoing management, rather than a one-off audit, is the single biggest difference between organisations that stay compliant comfortably and those that scramble every five years.

How Delta First delivers a compliant TM44 inspection

Delta First handles TM44 compliance as part of a wider HVAC and mechanical service, not as an isolated transaction. Our process runs in a clear sequence:

Pre-check: we review existing documentation, nameplate data, and O&M records to confirm scope and capacity before booking a site visit
Site inspection: an accredited assessor examines plant, controls, zoning, and maintenance history against CIBSE TM44 requirements
Report drafting: findings and improvement recommendations are written up in a clear, structured format
Statutory lodgement: the completed report is lodged on the government register, with proof of lodgement provided to you directly
Client handover: you receive the lodged report copy, a prioritised improvement roadmap, and costed options for any remedial works identified

Pro Tip: Ask your assessor to walk through the improvement roadmap with your PPM contractor in the same conversation. When the same organisation delivers both, as Delta First does, recommendations move into your maintenance schedule immediately instead of sitting unactioned for months.

Delta First serves commercial, education, healthcare, retail, and public sector clients across Essex, Suffolk, Norfolk, and Greater London, with typical lead times reflecting site complexity and how many systems require inspection. Whether you’re managing a single office or a multi-site portfolio, our engineers work directly with your estates team to keep the process straightforward and the paperwork defensible.

Why treat TM44 as a maintenance tool, not a compliance chore

Most guidance on TM44 treats it as a box to tick every five years, and that framing does facilities teams a disservice. The regulation exists to surface genuine inefficiency, and the reports that get filed and forgotten waste the one useful thing they produced: a professional assessment of where a building’s cooling systems are underperforming.

The conventional advice, book an assessor, get the certificate, move on, misses the point that recommendations without a delivery mechanism rarely happen at all. Facilities teams who see the best return treat the inspection as the start of a maintenance conversation, not the end of a compliance task. That means lining up a contractor capable of acting on findings before the report even lands, not scrambling to find one afterwards.

If there’s one priority worth taking from this, it’s sequencing: confirm your capacity, book the assessor, but have your remedial and maintenance partner already in the loop. Compliance and performance are the same problem viewed from two angles, and treating them separately is where most of the wasted energy, and wasted budget, actually happens.

Book a TM44 inspection with Delta First

Delta First is the direct route to a compliant TM44 report without juggling a separate assessor, a separate maintenance contractor, and a separate remedial works quote. As a single building services partner already covering HVAC, mechanical, electrical, and fabric compliance across Essex, Suffolk, Norfolk, and Greater London, we can inspect, lodge, and action recommendations under one accountable team, rather than passing your building between three different suppliers.

Booking with us gets you a site visit from an accredited assessor, a fully lodged TM44 report with proof of statutory lodgement, a prioritised improvement roadmap, and a fixed-cost quote for any remedial works identified on the day. If you already hold a PPM contract with us, we can schedule the inspection alongside existing visits to reduce disruption and cost.

To check whether your building needs an inspection or to get a fixed quote, visit our building services glossary for more on how compliance surveys fit alongside our wider maintenance and installation services, and get in touch to arrange a site visit.

TM44 inspection: does your building need one now?