TM44 for Multi-Tenant Buildings: 12kW & Shared AC Rules

Mixed-use and multi-tenant buildings create some of the most difficult TM44 compliance questions.

A single property may contain offices, shops, restaurants, leisure facilities and residential accommodation. The landlord may operate central cooling for common areas, while individual tenants own separate split, multi-split or VRF systems. Some equipment may serve several floors, while other units serve only one room.

That creates an important question: does the building need one TM44 inspection, several separate inspections, or none at all?

The answer does not depend only on the total number of air-conditioning units in the building. It depends on cooling capacity, system configuration and—most importantly—who controls the technical operation of each system.

This guide explains how TM44 for multi-tenant buildings works, how the 12kW threshold should be approached, where landlord and tenant responsibilities may divide, and what property managers should check before arranging an inspection.

This article primarily explains the requirements applying in England and Wales. Scotland and Northern Ireland operate under separate regulatory frameworks, so location should always be confirmed when assessing compliance.

The central TM44 rule

Air-conditioning systems with an effective rated output of more than 12kW must be inspected by an accredited air-conditioning energy assessor at intervals of no more than five years.

The 12kW threshold does not apply only to a single large unit. Several smaller units may need to be considered together when they form an air-conditioning system under the control of one person.

The official government guidance states that one or more air-conditioning units within a building controlled by a single person are considered a single air-conditioning system for the purposes of the regulations.

This means that five separate 3kW units could create a system with a combined effective rated output of 15kW. Although no individual unit exceeds 12kW, the combined system would be above the threshold.

You can read more about the general threshold in our guide to air-conditioning systems over 12kW and TM44 requirements.

Why multi-tenant buildings are more complicated

In a simple owner-occupied building, one organisation usually owns, manages and controls the entire air-conditioning installation. Establishing responsibility is relatively straightforward.

In a multi-let building, the position may look very different.

For example:

• The landlord controls central cooling serving reception, corridors and common areas.

• The landlord’s central system also supplies conditioned air to several tenant floors.

• One tenant has installed additional split systems in meeting rooms.

• Another tenant operates a separate VRF system throughout its demise.

• A retailer controls its own air conditioning under a full repairing and insuring lease.

• A facilities-management contractor handles maintenance but does not own the systems.

• Several unused units remain installed in a vacant part of the property.

All of these systems may be located at the same postal address, but they are not automatically treated as one compliance responsibility.

The correct approach is to map the systems, identify their effective rated outputs and establish who controls their technical operation.

Is the 12kW threshold calculated per unit, tenant or building?

There is no universal answer such as “per tenant” or “per building.”

The key questions are:

1. Which equipment forms part of the same air-conditioning system?

2. What is the combined effective rated output?

3. Who controls the technical operation of that equipment?

4. Which parts of the building does the system serve?

The physical building boundary is important, but it is not the only consideration. Control of the system can determine whether equipment should be grouped or treated separately.

Scenario 1: Several small units controlled by one tenant

A tenant occupies one office floor and controls five split systems rated at 3kW each.

Combined capacity:

5 × 3kW = 15kW

The tenant-controlled installation exceeds 12kW and is likely to fall within the inspection requirement, even though every individual unit is below the threshold.

Scenario 2: Separate systems controlled by separate tenants

A building contains three commercial tenants:

• Tenant A controls 8kW.

• Tenant B controls 9kW.

• Tenant C controls 10kW.

The combined capacity within the building is 27kW, but each system is independently controlled by a different tenant.

It should not automatically be assumed that all 27kW forms one system under single control. The leases, ownership arrangements, maintenance responsibilities and technical control should be reviewed before deciding how the regulations apply.

Scenario 3: One landlord-controlled system serving several tenants

A landlord owns and controls a central 90kW system serving three separately occupied floors.

Although several tenants benefit from the cooling, the equipment is under the landlord’s technical control. The system would normally be assessed as a landlord-controlled system rather than three unrelated tenant systems.

Scenario 4: Landlord system plus tenant-installed equipment

A landlord controls a 60kW central system. One tenant has also installed and controls an additional 18kW of split-system cooling.

In this situation, the landlord may be responsible for the central installation, while the tenant may be responsible for its independently controlled 18kW system.

Our guide to tenant-installed air conditioning and TM44 compliance explains why occupier alterations can create a separate compliance risk.

What does “control” actually mean?

Control means more than being able to adjust a wall-mounted thermostat.

Government guidance distinguishes between someone who controls the technical functioning of an air-conditioning system and someone whose involvement is limited to changing the temperature setting.

The person controlling the system may have authority over:

• Operation and technical management

• Maintenance arrangements

• Repair and replacement decisions

• System settings and operating schedules

• Appointment of HVAC contractors

• Access to plant and service records

• Decisions about commissioning, alteration or removal

The system owner will often be the controller. However, responsibility can be affected by lease terms, facilities-management contracts and the practical arrangements operating at the property.

Where an occupier takes full responsibility for the building and its services—for example, under some full repairing and insuring leases—the occupier may control the system.

Where tenants install their own equipment, responsibility will usually lie with those tenants because they own and control their systems.

A managing agent or maintenance contractor should not automatically be assumed to hold the legal responsibility simply because they arrange servicing. The contract must be examined to determine whether technical control has genuinely been transferred.

Even where a facilities-management or servicing company accepts relevant duties under a contract, government guidance explains that the landlord or occupier may retain a parallel duty to ensure the inspection has been completed.

For a fuller explanation, read our guide to TM44 legal responsibility for landlords, tenants and managing agents.

Can one TM44 report cover the entire building?

Potentially—but not in every case.

One report may be appropriate where the relevant systems are under single control and the assessment scope accurately covers the building and equipment concerned.

Separate reports or clearly separated assessment scopes may be appropriate where:

• Different parties independently control different systems.

• A tenant owns additional equipment outside the landlord’s control.

• Separate occupiers have independent maintenance and replacement responsibilities.

• Systems were installed at different times and have different compliance histories.

• The central plant and tenant systems require different levels of assessment.

• The building contains legally or operationally distinct areas.

The objective is not to create as many reports as possible. It is to ensure every system within scope is inspected under the correct responsible party and that the resulting documentation accurately reflects the property.

A report for the landlord’s central system should not be treated as automatic proof that every tenant-installed unit has also been covered.

Equally, a tenant’s report for a local split system does not demonstrate that the building’s central cooling plant is compliant.

Shared central plant in a mixed-use building

Shared plant commonly appears in office blocks, shopping centres, hotels, mixed-use developments and larger managed estates.

A central system may include:

• Chillers

• Rooftop packaged equipment

• VRF or VRV systems

• Air-handling units associated with cooling

• Fan-coil units

• Pumps and distribution equipment

• Heat-rejection equipment

• Building-management-system controls

• Zone controls and sensors

Where one organisation controls this plant, the assessment should consider the system as a whole—not merely the equipment visible inside individual tenant areas.

The assessor may need access to:

• Plant rooms

• Rooftop equipment

• External condensers

• Tenant floors

• Common areas

• Control panels

• Building-management-system information

• Maintenance and commissioning records

Restricted access can reduce the quality of the inspection and may prevent the assessor from verifying important parts of the system.

Property managers should therefore coordinate access with tenants before the appointment rather than waiting until the assessor arrives.

Does each tenant need a separate TM44 inspection?

Not necessarily.

A tenant does not need a separate report simply because it occupies a separate unit. The deciding factors are the system it controls and the effective rated output of that system.

A tenant may require its own inspection where it owns and technically controls air-conditioning equipment above the relevant threshold.

A tenant may not require a separate inspection where it only receives cooling from landlord-controlled central plant and has no independently controlled system within scope.

However, the tenant should still obtain appropriate evidence that the landlord-controlled system has a valid report—particularly where the lease places compliance-document obligations on the tenant or where evidence is required for an audit, transaction or internal compliance review.

Does the landlord’s 12kW calculation include tenant systems?

Not automatically.

If a tenant independently owns and controls its air-conditioning installation, that equipment may represent a separate system and responsibility.

However, this should be established from evidence rather than assumption. Buildings frequently contain unclear arrangements where:

• The landlord paid for the original installation.

• A tenant later modified the system.

• The service charge funds maintenance.

• The tenant controls local settings.

• The landlord approves repairs and replacement.

• A managing agent appoints the maintenance contractor.

• Equipment serves both demised and common areas.

In these cases, the party controlling the technical functioning may not be obvious from a visual inspection alone. The lease, service-charge provisions, planned preventative maintenance contract and asset ownership records may all be relevant.

Our article on TM44 and commercial property service charges explains the distinction between arranging or recovering the cost of compliance and holding the underlying responsibility.

What about residential parts of mixed-use buildings?

TM44 requirements concern air-conditioning systems in buildings rather than applying simply because a property has a commercial address.

Where a mixed-use development includes private residential accommodation, the precise building type, system use, system boundaries and regulatory treatment should be reviewed carefully.

A ground-floor shop with its own commercial AC system may require an inspection even where flats sit above it. Similarly, landlord-controlled cooling serving commercial common areas may need to be considered separately from domestic accommodation.

The safest approach is not to classify the entire development as “residential” or “commercial” without first mapping which systems serve which parts.

What about vacant units?

Vacancy does not necessarily remove a system from consideration.

An air-conditioning system may be switched off temporarily but remain installed, operational and capable of being returned to service. In that situation, the fact that a unit is currently empty does not automatically eliminate the compliance issue.

Important questions include:

• Is the equipment permanently decommissioned?

• Has refrigerant been removed?

• Has the electrical supply been permanently disconnected?

• Is the system recorded as redundant in the asset register?

• Could a new tenant use it without substantial recommissioning?

• Who remains responsible for the equipment while the unit is empty?

Read our detailed guidance on unused air-conditioning systems and TM44 compliance and TM44 requirements for vacant commercial properties.

Tenant fit-outs can change the compliance position

A building may have been compliant when a report was issued, but later fit-out works can change the system inventory and cooling capacity.

Typical changes include:

• Adding split systems to meeting rooms

• Installing supplementary cooling for IT rooms

• Replacing small systems with larger equipment

• Extending VRF systems into additional areas

• Altering zoning or controls

• Converting retail space into a restaurant or gym

• Dividing one office into several separately occupied suites

• Removing units without updating the asset register

The existing report should be checked to see whether it still represents the systems installed and controlled at the property.

If a lease is being assigned or a new occupier is completing a fit-out, use our practical guide to TM44 for lease assignments and tenant fit-outs.

For newly installed equipment, our article on new air-conditioning installations and TM44 inspections explains when the first inspection becomes due.

Worked example: a five-storey mixed-use building

Consider a five-storey property containing:

• Ground-floor retail unit

• Ground-floor café

• Three office floors

• Shared reception and corridors

• Central landlord-controlled cooling

• Tenant-installed split systems

• A separate server-room cooling unit

The equipment is recorded as follows:

System	Cooling capacity	Controller
Central system serving reception, corridors and offices	85kW	Landlord
Retail tenant’s split systems	14kW	Retail tenant
Café cooling system	10kW	Café tenant
Second-floor supplementary meeting-room units	9kW	Office tenant
Server-room cooling	8kW	Same office tenant

The landlord-controlled central system clearly exceeds 12kW and requires inspection.

The retail tenant’s independently controlled 14kW installation also exceeds 12kW and may require its own inspection.

The café controls only 10kW, so it appears below the threshold when considered independently.

The office tenant controls 9kW of meeting-room cooling and 8kW of server-room cooling. If those units are considered part of the air-conditioning system under that tenant’s single control, the combined capacity is 17kW. The tenant should not assume it is outside the requirement merely because each group is below 12kW.

This example demonstrates why counting units by floor is not enough. The assessor or compliance manager must establish system grouping and technical control.

Illustrative case study: the report covered the address, but not every system

A managing agent takes over a multi-let office and retail property. The compliance file contains a TM44 report carrying the correct building address, so the property is initially recorded as compliant.

During a later review, the agent discovers that the report covers only the landlord’s original central plant. Since that inspection:

• Two tenants installed supplementary split systems.

• One retail unit changed use.

• The AC asset register was never updated.

• Maintenance records were held by three different contractors.

• No one had checked whether the tenant systems separately exceeded 12kW.

The managing agent creates a revised asset register identifying system ownership, capacity, location and controller. The review establishes that one tenant controls more than 12kW of additional cooling and needs separate compliance action.

The key lesson is simple: a report bearing the property address is not enough. Its scope must match the systems currently installed and the parties controlling them.

The compliance documents every multi-let building should maintain

A reliable building-level compliance file should contain:

1. Current air-conditioning asset register

2. Manufacturer and model information

3. Cooling output for each unit

4. System grouping and areas served

5. Equipment ownership

6. Named party controlling each system

7. Current maintenance contracts

8. Commissioning and handover documents

9. Previous TM44 reports and certificate numbers

10. Government lodgement evidence

11. F-Gas records where applicable

12. Lease clauses relevant to plant and compliance

13. Details of tenant alterations and fit-outs

14. Records of removed or decommissioned equipment

15. Next inspection dates and responsible contacts

A well-maintained air-conditioning asset register for TM44 inspections can reduce uncertainty, prevent omissions and help the assessor quote accurately.

You can also use our TM44 compliance-file checklist to organise the evidence.

TM44 is not the same as maintenance or F-Gas compliance

A common mistake is assuming that regular air-conditioning servicing proves TM44 compliance.

It does not.

Planned maintenance, F-Gas leak checks and TM44 inspections serve different purposes.

A maintenance contractor may clean filters, repair equipment and test operation. F-Gas requirements deal with refrigerant management and leak-control obligations. A TM44 inspection assesses the energy efficiency, sizing, controls, maintenance condition and operation of the air-conditioning system.

A maintenance certificate is not a substitute for a lodged TM44 air-conditioning inspection report.

Our comparison of TM44 and F-Gas inspections explains the differences in greater detail.

Can representative sampling be used?

Large multi-tenant buildings may contain many similar systems. Appropriate representative sampling can sometimes form part of the TM44 assessment methodology, depending on system type, consistency, available records and the assessor’s professional judgement.

Sampling does not mean ignoring unrecorded equipment.

The assessor still needs a credible understanding of:

• The complete system inventory

• Installed capacities

• System types

• Control arrangements

• Maintenance condition

• Areas served

• Differences between representative and non-representative equipment

Poor asset information can make responsible sampling difficult and may increase the time and cost of the inspection.

Read our guide explaining whether a TM44 assessor must inspect every AC unit.

Who should coordinate the inspection?

For a mixed-use or multi-tenant property, one person should coordinate the building-level process even where several parties ultimately hold separate responsibilities.

This could be:

• Building owner

• Property manager

• Facilities manager

• Managing agent

• Compliance manager

• Lead tenant

• Appointed FM contractor

The coordinator should not assume this appointment transfers every legal responsibility. Their practical role is to gather information, arrange access, identify responsible parties and make sure no system is omitted.

Our guide to TM44 inspections for managing agents and property portfolios provides a wider framework for controlling multiple properties and renewal dates.

Preparing for the assessor

Before requesting a quotation, gather as much of the following as possible:

• Full property address

• Building use and number of floors

• Names of occupiers

• AC asset list

• Approximate number of indoor and outdoor units

• Cooling capacities

• Details of chillers, VRF/VRV, AHUs and fan-coil systems

• Previous TM44 report

• Maintenance records

• Floor plans

• Plant-room and roof-access information

• Name and telephone number of the site contact

• Any known access restrictions

• Confirmation of which systems are landlord- or tenant-controlled

If complete information is unavailable, photographs of equipment and model-number labels can help establish the likely scope.

Our TM44 company checklist before booking explains how to prepare for an efficient inspection.

Common mistakes in multi-tenant buildings

The most frequent compliance errors include:

Adding every unit in the building without checking control

The total building capacity may be useful, but it does not by itself establish how responsibilities divide.

Assuming each tenant is assessed separately

Several systems serving different areas may still form one system under single control.

Assuming the landlord’s report covers tenant installations

The report must be checked against the actual equipment included in its scope.

Treating thermostat access as technical control

Changing room temperature is not the same as controlling the technical functioning of the system.

Ignoring small units

Several small systems can exceed 12kW when combined.

Relying only on maintenance records

Maintenance does not replace a valid TM44 inspection and government-lodged report.

Forgetting fit-out changes

New tenant equipment can change the compliance position after the original inspection.

Failing to plan access

Locked plant rooms, inaccessible roofs and unavailable tenant areas can delay or restrict the inspection.

What happens after the inspection?

Following the inspection, the accredited assessor prepares an air-conditioning inspection report addressing matters such as:

• Likely system efficiency

• Maintenance condition

• Installed controls and settings

• Potential faults

• System sizing in relation to cooling demand

• Opportunities to improve performance

• Key recommendations

The report must be lodged on the official register to be valid. Reports produced on or after 6 April 2012 contain a unique report reference number generated through lodgement.

There is generally no legal obligation under the TM44 regime itself to carry out every recommendation. However, implementing suitable measures can reduce energy consumption, operating costs and unnecessary equipment wear.

Read our guide to TM44 report recommendations to understand what happens after the assessment.

A practical decision process

When reviewing a mixed-use or multi-tenant building, use this sequence:

1. List every air-conditioning unit and system.

2. Record the effective rated output.

3. Identify which equipment works together.

4. Record which areas each system serves.

5. Establish who owns each system.

6. Establish who controls its technical operation.

7. Aggregate relevant equipment under common control.

8. Compare each system’s combined output with the 12kW threshold.

9. Check existing reports against the current installation.

10. Arrange any required inspection with an accredited assessor.

11. Store the lodged report and renewal date in the compliance file.

12. Review the position whenever a tenant, lease or system changes.

Arrange a TM44 scope review for your building

TM44.uk helps landlords, tenants, facilities managers and managing agents assess complex air-conditioning arrangements across mixed-use and multi-tenant buildings.

We can review your available asset information, identify the likely inspection scope and arrange an accredited TM44 air-conditioning energy assessor anywhere in the UK.

Our service can include:

• Pre-inspection scope review

• Assessment of asset information

• Accredited TM44 inspection

• Representative sampling where technically appropriate

• Inspection of central and tenant-controlled systems

• TM44 report and certificate

• Government lodgement

• Portfolio and multi-site coordination

• Clear guidance on the information required before attendance

To receive a quotation, send us the property address, asset list, previous report and any available information about landlord- and tenant-controlled systems.

Request your TM44 inspection quotation or contact the TM44.uk team for assistance.

Final takeaway

TM44 compliance in a multi-tenant building cannot be determined simply by counting units or adding every cooling output shown on the property’s maintenance schedule.

The correct assessment depends on:

• Which equipment forms each system

• The combined effective rated output

• Who controls the technical operation

• Which areas are served

• Whether existing reports cover the current installation

A landlord may be responsible for shared central plant while a tenant is responsible for separately installed equipment. One report may cover a complete system under single control, but it should never be assumed to cover unrelated systems merely because they share the same address.

The safest approach is to create an accurate asset register, establish control, check the scope of existing reports and obtain advice from an accredited assessor where the position is unclear.

Authoritative guidance is available from the UK Government’s guide to air-conditioning inspections and CIBSE TM44 guidance.